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Disrupted Self-Perception in People With Chronic Low Back Pain. Further Evaluation of the Fremantle Back Awareness Questionnaire

Open AccessPublished:June 17, 2016DOI:https://doi.org/10.1016/j.jpain.2016.06.003

      Highlights

      • The questionnaire appears to be a sound way of assessing altered self-perception of the back.
      • The level of altered self-perception is positively correlated with pain intensity and disability.
      • Self-perception is also associated with distress, pain related cognitions and sensitivity.
      • Self-perception appears a more important determinant of clinical severity than these factors.

      Abstract

      Several lines of evidence suggest that body perception is altered in people with chronic back pain. Maladaptive perceptual awareness of the back might contribute to the pain experience as well as serve as a target for treatment. The Fremantle Back Awareness Questionnaire (FreBAQ) is a simple questionnaire recently developed to assess back-specific altered self-perception. The aims of this study were to present the outcomes of a comprehensive evaluation of the questionnaire's psychometric properties and explore the potential relationships between body perception, nociceptive sensitivity, distress, and beliefs about back pain and the contribution these factors might play in explaining pain and disability. Two hundred fifty-one people with chronic back pain completed the questionnaire as well as a battery of clinical tests. The Rasch model was used to explore the questionnaires' psychometric properties and correlation and multiple linear regression analyses were used to explore the relationship between altered body perception and clinical status. The FreBAQ appears unidimensional with no redundant items, has minimal ceiling and floor effects, acceptable internal consistency, was functional on the category rating scale, and was not biased by demographic or clinical variables. FreBAQ scores were correlated with sensitivity, distress, and beliefs and were uniquely associated with pain and disability.

      Perspective

      Several lines of evidence suggest that body perception might be disturbed in people with chronic low back pain, possibly contributing to the condition and offering a potential target for treatment. The FreBAQ was developed as a quick and simple way of measuring back-specific body perception in people with chronic low back pain. The questionnaire appears to be a psychometrically sound way of assessing altered self-perception. The level of altered self-perception is positively correlated with pain intensity and disability as well as showing associations with psychological distress, pain catastrophization, fear avoidance beliefs, and lumbar pressure pain threshold. In this sample, it appears that altered self-perception might be a more important determinant of clinical severity than psychological distress, pain catastrophization, fear avoidance beliefs, or lumbar pressure pain threshold.

      Key words

      Low back pain (LBP) is currently the leading cause of disability worldwide
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      Figure 1The maladaptive perceptions model. Abbreviation: Dx, diagnosis.
      In this model maladaptive beliefs and maladaptive body image are seen as mutually reinforcing, contributing to the persistence of LBP

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      Assessing self-perception in patients with chronic low back pain: Development of a back-specific body-perception questionnaire.
      Some minor changes were also made to the wording of the questionnaire on the basis of feedback from participants in this preliminary study.
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      Assessing self-perception in patients with chronic low back pain: Development of a back-specific body-perception questionnaire.
      The aim of this article is to report on the initial testing of the updated questionnaire in a large heterogeneous sample of people with CLBP, particularly to present the outcomes of a comprehensive evaluation of the scale's psychometric properties using a Rasch analysis, and the modifications to the scale that these data might suggest. We also aimed to explore the potential relationships between body perception, nociceptive sensitivity, distress and beliefs about back pain, and the combined and unique contribution these factors might play in explaining pain and disability in this population.

      Methods

       Design

      This cross-sectional cohort study was approved by the Human Research Ethics Committees of Curtin University, Royal Perth Hospital, and Sir Charles Gairdner Hospital in Perth, Western Australia. The data presented were collected as part of a larger study undertaking extensive biopsychosocial profiling of people with persistent LBP, the results of which have been reported elsewhere.
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      All participants provided informed consent and all procedures conformed to the Declaration of Helsinki.

       Participants

      People with axial CLBP were recruited from 2 metropolitan hospitals in Perth, Western Australia (1.4%), private metropolitan physiotherapy clinics (20.1%), pain management and general practice clinics (1.0%), and via multimedia advertisements circulated throughout the general community in metropolitan and regional Western Australia (77.6%). Willing volunteers were asked to contact one of the researchers (M.I.R.) directly by telephone or e-mail, and were then sent a screening questionnaire. All questionnaire responses were screened and ambiguous responses clarified in telephone communication.
      Volunteers were included if they were aged between 18 and 70 years, were fluent in written and spoken English, had experienced LBP for >3 months, scored ≥2 on a numeric rating scale (NRS) for average pain intensity in the past week anchored with 0 = “no pain,” and 10 = “worst pain imaginable,” and ≥5 on the Roland Morris Disability Questionnaire (RMDQ).
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      In addition participants needed a score of at least 60% LBP on the following question
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      minimizing the likelihood of participants with primarily radicular pain being entered into the study.
      Volunteers were excluded if they reported any previous extensive spinal surgery (greater than single-level fusion or discectomy) or any type of spinal surgery within the past 6 months, were diagnosed with serious spinal pathology (cancer, inflammatory arthropathy, or acute vertebral fracture), had been diagnosed with a neurological disease, experienced bilateral pain at the dorsum of the wrist/hand, or were currently pregnant.

       Procedure

      Only procedures relevant to this study are presented. For a fuller description of all testing undertaken see Rabey et al.
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      On initial presentation, all participants were screened for eligibility—including the presence of red flag conditions, given information about the project, and invited to sign a consent form. Participants then provided basic demographic information and had their height and weight measured, from which their body mass index (BMI) was calculated.
      All participants next completed a questionnaire that solicited information about the length of the current episode, pain distribution, current pain medications, and the presence of any comorbidities. In addition, the participants completed a set of standardized surveys that assessed disability, pain, and psychological functioning. LBP-related disability was measured using the RMDQ.
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      with the average score for the 3 subscales used for analysis. Finally, participants completed the FreBAQ (Supplemental Appendix 1).
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      The original study involved an extensive sensory profiling of the participants using a combination of clinical bedside tests and laboratory tests.
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      Pressure was increased at a rate of 50 kPa/s until the participant indicated their pressure pain threshold by pressing a button. Thirty-second interstimulus intervals were adopted to reduce the possibility of temporal summation. The mean of 3 threshold recordings was used for analysis.
      Heat pain threshold (HPT), the temperature at which a sensation of warmth becomes the first sensation of heat and pain,
      • Rolke R.
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      • Treede R.D.
      • Beyer A.
      • Binder A.
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      Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): Standardized protocol and reference values.
      was tested using the Thermotest (Somedic AB). Testing began at 32°C and increased by 1°C/s until the participant indicated their HPT by pressing a button, or the device's upper temperature limit was reached (50°C). Thirty-second interstimulus intervals were adopted and the mean of 3 threshold recordings was used for the analysis.
      Cold pain threshold was recorded as the point at which the sensation of cold became the first sensation of cold and pain.
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      Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): Standardized protocol and reference values.
      The same equipment for testing HPT was used for testing cold pain threshold. Testing began at 32°C and the temperature of the thermode decreased by 1°C/s until the participant detected their threshold and pressed a button, or the device's lower temperature limit was reached (4°C). Thirty-second interstimulus intervals were adopted and the mean of 3 threshold recordings was used for analysis.

       Sample Size

      The sample size requirement for this study was not determined a priori because the sample was recruited as part of an extensive study exploring multidimensional subgrouping in a CLBP population. The sample size of 251 provided .8 power to detect potentially meaningful independent associations of FreBAQ with pain and disability (ie, R2 of .03 or more in regression models after adjusting for covariates) at α < .05 (G*Power version 3.1.9), was well over the minimum requirements for the number of subjects per variable for unbiased regression coefficients and model R2 estimates in linear regression analyses,
      • Austin P.C.
      • Steyerberg E.W.
      The number of subjects per variable required in linear regression analyses.
      and was in excess of the 243 persons recommended to ensure item calibration stability within ± .5 logits with 99% confidence.
      • Linacre J.M.
      Sample size and item calibration stability.

       Data Analysis

       Sample Description

      Descriptive statistics were used to describe the demographic and clinical characteristics of the sample. The FreBAQ was summarized with range, median, mean, and standard deviation measures reported for the total score. The frequencies in each response category were also reported.

       Psychometrics

      We used Rasch analysis (Winsteps v3.73.0 software; Winsteps, Beaverton, Oregon) to assess the psychometric properties of the FreBAQ (see Bond and Fox
      • Bond T.G.
      • Fox C.M.
      Applying the Rasch Model: Fundamental Measurement in the Human Sciences.
      for a comprehensive overview of Rasch analysis). The Andrich Rating Scale model was chosen because the FreBAQ items all share the same rating scale.
      • Linacre J.
      Comparing “partial credit” and “rating scale” models.
      The following components were assessed: item hierarchy, category order, targeting, unidimensionality, person fit, internal consistency, and differential item functioning.
      • Tennant A.
      • Conaghan P.G.
      The Rasch measurement model in rheumatology: What is it and why use it? When should it be applied, and what should one look for in a Rasch paper?.
      Item hierarchy allows for the assessment of construct validity. The FreBAQ was developed to assess body perceptual impairments in people with back pain. We compared the item hierarchy to ensure the items were ordered in a logical manner, from comparatively mild perceptual impairments to more severe impairments. Item reliability >.9 was considered sufficient to confirm the item hierarchy.

      Linacre J: A User’s Guide To Winsteps, Ministep Rasch-Model Computer Programs, Program Manual 3.74.0. Beaverton, Winsteps.com, 2012

      Category ordering was assessed to determine how the sample used the rating scale. The FreBAQ has 5 response categories (0–4) and thus 4 step-calibrations, thresholds at which the likelihood of endorsing 1 category is equal to that of endorsing the next were assessed. Respondents with high overall scores are expected to endorse higher categories on any given item. We assessed whether each of the 5 categories were used and whether the respondents used each category in the expected manner.
      Targeting refers to how well the FreBAQ items targeted the sample. It was assessed by visual inspection of the distribution of persons and item threshold averages and through comparison of the summary statistics. The average item endorsability was anchored at 0 logits; therefore positive average person agreeability would suggest the sample experienced perceptual impairments more frequently than the average of the scale. A negative average person value would suggest the opposite.
      • Tennant A.
      • Conaghan P.G.
      The Rasch measurement model in rheumatology: What is it and why use it? When should it be applied, and what should one look for in a Rasch paper?.
      For questionnaire items to be validly summated to provide an overall measure of a construct, the questionnaire items must collectively assess 1 construct at a time. In this case, the FreBAQ intends to measure ‘perceptual impairment,’ thus each item should assess a component of this construct. That is, each item should share in common an aspect of perceptual impairment yet be sufficiently different so as not to be redundant. Assessment of unidimensionality seeks to identify clusters of items that together may be assessing a secondary dimension, thus threatening measurement of the primary dimension. Unidimensionality was assessed through analysis of item fit statistics and through principal components analysis (PCA) of residuals.
      • Smith E.V.
      Detecting and evaluating the impact of multidimensionality using item fit statistics and principal component analysis of residuals.
      The χ2 based fit statistics, reported as mean-squares (in logits), have an expected value of 1 logit. Fit was considered excessive if >1.4 or <.6 logits
      • Wright B.D.
      • Linacre J.M.
      • Gustafson J.
      • Martin-Lof P.
      Reasonable mean-square fit values.
      and information-weighted fit statistic and outlier-sensitive fit statistic (outfit) were analyzed. The item characteristic curves of misfitting items were visually inspected to assess item performance across the person agreeability range. The PCA residual correlation matrix was inspected visually to identify the presence of secondary dimensions. Item clusters with substantial positive or negative loadings equivalent to an eigenvalue >2 were reviewed to ascertain whether a second dimension was present.
      • Raîche G.
      Critical eigenvalue sizes in standardized residual principal components analysis.
      PCA also allows for a test of local independence of items
      • Tennant A.
      • Conaghan P.G.
      The Rasch measurement model in rheumatology: What is it and why use it? When should it be applied, and what should one look for in a Rasch paper?.
      and is used to identify redundant items. Large positive correlations >.5 were considered indicative of local dependence where the response to 1 item relies on the response to the other.
      Assessment of person fit identifies people who responded in an unexpected manner. Person fit was considered excessive if the outfit statistics were >2 logits.
      • Tennant A.
      • Conaghan P.G.
      The Rasch measurement model in rheumatology: What is it and why use it? When should it be applied, and what should one look for in a Rasch paper?.
      Misfitting persons were compared across variables with those who fit the model using a χ2 test of significance (gender) or an independent samples t-test (FreBAQ total score, age, pain intensity [NRS], disability [RMDQ], and BMI). Response strings of those misfitting persons were visually analyzed to identify patterns in their responses.
      The Winsteps software provides 2 measures of internal consistency; the Rasch-specific ‘person reliability index’ and the more widely recognized Cronbach α.
      • Fox C.M.
      • Jones J.A.
      Uses of Rasch modeling in counseling psychology research.
      Acceptable internal consistency is considered to be >.7 in both instances.
      • Portney L.G.
      • Watkins M.P.
      Foundations of Clinical Research: Applications to Practice.
      • Tennant A.
      • Conaghan P.G.
      The Rasch measurement model in rheumatology: What is it and why use it? When should it be applied, and what should one look for in a Rasch paper?.
      The FreBAQ items should function similarly for all persons of the same level of agreeability. Differential item functioning identifies whether characteristics other than the latent construct alters the functioning of the item (eg, male and female respondents with the same level of perceptual impairment endorse an item differently). We assessed whether age, gender, pain intensity, or disability biased the functioning of the scale by splitting the sample, according to median, and comparing the 2 subgroups. BMI was split according to underweight/healthy weight (<25) and overweight/obese (≥25). Items with statistically significant (P < .05) contrasts > .5 logits were further explored.
      • Alagumalai S.
      • Curtis D.D.
      • Hungi N.
      Applied Rasch Measurement: A Book of Exemplars.

       Relationship to Clinical Status

      The association between FreBAQ scores and 1) demographic characteristics (age, gender, BMI), 2) clinical status (pain and disability), 3) cognitive/psychological characteristics, and 4) nociceptive sensitivity measures, were assessed using correlation statistics (Pearson R, Spearman ρ, or point-biserial coefficient as appropriate). Multivariable linear regression analysis was used to estimate the unique association of FreBAQ scores with pain and disability adjusted for demographic, cognitive/psychological factors, and sensitivity measures. A 3-step process was used, by first evaluating the univariate association of each independent variable with the dependent variable, then estimating a multivariable model retaining those variables associated with the dependent variable at P < .1 (model 1), then estimating a final model (model 2) retaining only those independent variables statistically significant at P < .1 from model 1. Forward and backward stepwise variable selection was also performed and confirmed the stability of the final models (probability of entry/removal P = .05). For the disability model the log-transformed RMDQ was used as the dependent variable because of the skewed distribution of the measure. For the pain model the NRS for average pain in the past week was used as the dependent variable. Models were examined for absence of influential observations and multicollinearity, linearity of associations, and normality and homoscedasticity of residuals. Standardized β coefficients with 95% confidence intervals are reported to allow comparison of strength of associations. The total variance in disability and pain explained by each final model (R2) was partitioned into unique variance attributable to FreBAQ and other variables in the model, and shared variance, by examination of squared semipartial correlations between variables and outcome.

      Results

       Sample Characteristics

      Five hundred eighty-five volunteers were screened for eligibility. Two hundred ninety-two were excluded for the following reasons: low RMDQ score (n = 130), age >70 years (n = 42), dominant leg pain (n = 28), bilateral wrist pain (n = 23), suspected serious spinal pathology (n = 8), low pain intensity (n = 6), and failed to complete baseline assessment (n = 55). Of the 293 eligible participants the first 42 completed a pilot version of the FreBAQ
      • Wand B.M.
      • James M.
      • Abbaszadeh S.
      • George P.J.
      • Formby P.M.
      • Smith A.J.
      • O’Connell N.E.
      Assessing self-perception in patients with chronic low back pain: Development of a back-specific body-perception questionnaire.
      and their data were not used in this analysis. The remaining 251 participants completed the updated version of the questionnaire.
      • Wand B.M.
      • James M.
      • Abbaszadeh S.
      • George P.J.
      • Formby P.M.
      • Smith A.J.
      • O’Connell N.E.
      Assessing self-perception in patients with chronic low back pain: Development of a back-specific body-perception questionnaire.
      There were no differences in gender (P = .127), age (P = .107), disability (RMDQ, P = .424), or pain (NRS, P = .608) between those completing the pilot versus updated version. Demographic and clinical characteristics of the 251 included participants are shown in Table 1.
      Table 1Participants Demographic and Clinical Information (N = 251)
      CharacteristicMean (SD), Median (IQR) or N (%)
      Demographic information
       Gender (female)148 (59.0%)
       Age, y48.8 (13.4)
       Height, cm170.9 (9.8)
       Weight, kg80.6 (16.7)
       Body mass index27.6 (5.2)
       Work status
      At work (or studying)188 (74.9)
      Off work63 (25.1)
      Clinical status
       Duration of LBP, mo
      Data missing for 4 cases.
      120 (42–240)
       Pain area
      Back pain only121 (48.2%)
      Back pain and leg pain130 (51.8%)
       Taking opioid medication40 (15.9%)
       Average back pain intensity (scale of 0–10)5.8 (1.9)
       Disability (RMDQ; scale of 0–24)9 (6–13)
       Pain catastrophization (PCS; scale of 0–52)
      Data missing for 1 case.
      18.8 (12.0)
       Fear avoidance (FABQ-PA; scale of 0–24)14.1 (6.0)
       Psychological distress (DASS-21, scale of 0–42)8.0 (4.0–12.7)
      Abbreviations: IQR, interquartile range; RMDQ, Roland Morris Disability Questionnaire; PCS, Pain Catastrophizing Scale; FABQ-PA, Fear Avoidance Beliefs Questionnaire, physical activity subscale; DASS-21, Depression Anxiety Stress Scale 21.
      Data missing for 4 cases.
      Data missing for 1 case.
      The average total FreBAQ score was 9.8 (SD = 6.6) with a median score of 9.0 (interquartile range = 4.0–14.0). Table 2 shows a full description of the frequency of response for each questionnaire item.
      Table 2Frequency of Responses to Each Item of the FreBAQ (N = 251)
      ItemNever, n (%)Rarely, n (%)Occasionally, n (%)Often, n (%)Always, n (%)MedianMean
      1. My back feels as though it is not part of the rest of my body143 (57.0)47 (18.7)29 (11.5)25 (10.0)7 (2.8)0.8
      2. I need to focus all my attention on my back to make it move the way I want it to58 (23.1)46 (18.3)81 (32.3)51 (20.3)15 (6.0)21.7
      3. I feel as if my back sometimes moves involuntarily, without my control144 (57.4)52 (20.7)33 (13.2)19 (7.6)3 (1.2)0.7
      4. When performing everyday tasks, I don't know how much my back is moving104 (41.4)75 (29.9)39 (15.5)29 (11.6)4 (1.6)11.0
      5. When performing everyday tasks, I am not sure exactly what position my back is in99 (39.4)67 (26.7)45 (17.9)31 (12.4)9 (3.6)11.1
      6. I can't perceive the exact outline of my back125 (49.8)61 (24.3)29 (11.6)25 (10.0)11 (4.4)1.9
      7. My back feels like it is enlarged (swollen)123 (49.0)29 (11.6)47 (18.7)35 (13.9)17 (6.8)11.2
      8. My back feels like it has shrunk184 (73.3)32 (12.8)20 (8.0)10 (4.0)5 (2.0)0.5
      9. My back feels lopsided (asymmetrical)84 (33.5)25 (10.0)48 (19.1)59 (23.5)35 (13.9)21.7
      Abbreviation: FreBAQ, Fremantle Back Awareness Questionnaire.

       Psychometrics

      Rasch analysis was performed on the data from 251 participants. Fifteen (6%) persons registered a minimum score and no persons registered a maximum score, suggesting ceiling and floor effects of the scale are negligible.
      Table 3 shows the average item endorsability thresholds in hierarchal order, where higher thresholds indicate items that are harder to endorse. Item 9 (My back feels lopsided) was the easiest to endorse and item 8 (My back feels like it has shrunk) was the most difficult to endorse. The item order appeared to progress in a largely coherent fashion, from the comparatively lesser perceptual impairments (eg, item 9, My back feels lopsided) to the more severe impairments (eg, item 1, My back feels as though it is not part of the rest of my body), suggesting the FreBAQ has construct validity. An item reliability of .97 suggested the sample size was sufficient to confirm the item hierarchy is reproducible. Interestingly, item 8 (My back feels like it has shrunk) was significantly more difficult to endorse than the other items and did not fit the predicted hierarchal order.
      Table 3Average Item Endorsability Thresholds, Shown in Hierarchal Order, and Fit Statistics, for the FreBAQ Scores of Respondents With Back Pain (N = 251)
      ItemFreBAQ
      Measure (Logits)Score
      Raw score of 1004 (possible score of 4 × 251 participants).
      Infit (mnsq)Outfit (mnsq)
      8.821221.41.7
      3.391871.21.2
      1.272081.21.4
      6.13235.9.8
      4.03256.7.7
      5−.1286.8.8
      7−.152961.01.0
      2−.66421.91.0
      9−.734381.21.2
      Abbreviations: FreBAQ, Fremantle Back Awareness Questionnaire; Infit, information-weighted fit statistic; Outfit, outlier-sensitive fit statistic; mnsq, mean-squares.
      NOTE. Higher measures indicate harder to endorse items and lower measures indicate easier to endorse items.
      Raw score of 1004 (possible score of 4 × 251 participants).
      Visual inspection of the category structure suggested the respondents used the categories in the expected manner although category 1 (rarely) was underused and did not have an interval on the latent variable (Fig 2).
      Figure thumbnail gr2
      Figure 2Probability curves for the 5-category Fremantle Back Awareness Questionnaire (FreBAQ; C0 = Never, C1 = Rarely, C2 = Occasionally, C3 = Sometimes, C4 = Always). Note the disordered threshold for C1.
      The person-item distribution map shown in Fig 3 highlights the targeting of the FreBAQ to the sample. The sample was loaded toward less frequent experiences of perceptual impairment compared with the average item endorsability. The average (SD) person agreeability was −.96 (.84) logits (range = −2.92 to 1.85 logits), compared with the default average (SD) item endorsability of 0 (.46) logits (range = −.73 to .82 logits).
      Figure thumbnail gr3
      Figure 3Item-person threshold map for the Fremantle Back Awareness Questionnaire (FreBAQ). Persons who rarely experience perceptual impairments and items easier to endorse are located on the left side of the logit scale (ie, <0 logits); Persons who regularly experience perceptual impairments and items harder to endorse are located to the right of the logit scale (ie, >0 logits). Average item endorsability is set at 0 logits by default.
      The FreBAQ items constituted a unidimensional scale. Table 3 shows a summary of the fit statistics for the 9 items. Item 8 showed excessive positive outfit (1.7 logits) and analysis of the item characteristic curves suggested the misfit was due to respondents with higher scores overall scoring this item low. Visual inspection of the PCA correlation matrix suggested items 4 (When performing everyday tasks, I don't know how much my back is moving), 5 (When performing everyday tasks, I am not sure exactly what position my back is in), and 6 (I can't perceive the exact outline of my back) could plausibly constitute a second dimension. However, an eigenvalue of 2.0 suggested the scale could be considered unidimensional.
      • Raîche G.
      Critical eigenvalue sizes in standardized residual principal components analysis.
      Assessment of local dependence revealed no meaningful relationships between the FreBAQ item residuals, suggesting none of the questions are redundant.
      Twenty-three persons (9%) showed excessive outfit. Comparatively, misfitting persons were significantly older (P = .02) and in more pain (P = .002). Visual analysis of the response strings of the misfitting persons revealed no meaningful patterns. Typically, persons with higher scores unexpectedly ranked an item low or, less commonly, persons with low scores overall scored an item high.
      A person reliability index of .74 and Cronbach α value of .80 indicated that the internal consistency of the FreBAQ was adequate.
      • Tennant A.
      • Conaghan P.G.
      The Rasch measurement model in rheumatology: What is it and why use it? When should it be applied, and what should one look for in a Rasch paper?.
      Analysis of differential item functioning suggested age may influence responses to item 8. Older persons (n = 128) reported item 8 (.61 logits) easier to endorse than younger persons (n = 123), however, this difference was not statistically significant (P = .054) and should be viewed with caution because of the number of comparisons. No other statistically significant contrasts >.5 logits were observed, suggesting the items were not otherwise biased by the respondents’ age, gender, pain, disability, or BMI.

       Relationship to Clinical Status

      The FreBAQ showed significant initial bivariate association with BMI, disability, pain intensity, pain catastrophization, fear avoidance, psychological distress, and lumbar pressure pain threshold (Table 4).
      Table 4Correlations of Demographic Characteristics, Clinical Status, Cognitive/Psychological Characteristics and Psychophysical Measures Using the FreBAQ
      CharacteristicCorrelation CoefficientP
      Gender (female)−.023.714
      Age, y−.087.166
      BMI.161.011
      Duration of LBP, mo.084.188
      Disability (RMDQ).319<.001
      Average back pain intensity.265<.001
      Pain catastrophization (PCS).358<.001
      Fear avoidance (PABQ-PA).263<.001
      Psychological distress (DASS-21).376<.001
      Lumbar pressure pain threshold−.139.028
      Lumbar cold pain threshold.112.078
      Lumbar heat pain threshold−.077.222
      Abbreviations: FreBAQ, Fremantle Back Awareness Questionnaire; BMI, body mass index; LBP, low back pain; RMDQ, Roland Morris Disability Questionnaire; PCS, Pain Catastrophizing Scale; PABQ-PA, Fear Avoidance Beliefs Questionnaire, physical activity subscale; DASS-21, Depression Anxiety Stress Scale 21.
      NOTE: Significant associations in bold.
      Table 5 shows the standardized β coefficients for linear regression models for disability (logRMDQ). Alone, the FreBAQ score explained 12.4% of the variance in disability. The final model retaining FreBAQ score, psychological distress, BMI, and pain intensity, explained 29.5% of the variance in disability. Of this, FreBAQ uniquely contributed 1.3%, whereas 13.4% was shared between all 4 variables. Psychological distress, BMI, and pain intensity uniquely contributed 6.1%, 2.6%, and 6.1%, respectively. In the final model, an increase of 1 SD in the FreBAQ score was estimated to be associated with an increase in .13 SD of logRMDQ (95% confidence interval, .01–.25; P = .032).
      Table 5Linear Regression Models for Disability (logRMDQ)
      UnivariableMultivariable 1Multivariable 2
      β (95% CI)
      Standardized β coefficient represented expected change in SD units of logRMDQ for 1 SD change in independent variable.
      Pβ (95% CI)
      Standardized β coefficient represented expected change in SD units of logRMDQ for 1 SD change in independent variable.
      Pβ (95% CI)
      Standardized β coefficient represented expected change in SD units of logRMDQ for 1 SD change in independent variable.
      P
      Back perception (FreBAQ).35 (.23–.47)<.001.10 (−.02 to .23).096.13 (.01–.25).032
      Psychological distress (DASS-21).41 (.29–.52)<.001.22 (.09–.36).001.28 (.16–.40)<.001
      Pain catastrophization (PCS).33 (.21–.45)<.001.06 (−.07 to .20).339
      Fear avoidance (PABQ-PA).22 (.10–.34)<.001.09 (−.02 to .21).110
      BMI.34 (.12–.36)<.001.16 (.06 to .27).003.16 (.06–.27).003
      Lumbar pressure pain threshold−.15 (−.30 to −.03).021−.03 (−.14 to .08).594
      Average back pain intensity (scale of 0–10).37 (.25–.49)<.001.26 (.15–.37)<.001.26 (.15–.37)<.001
      Abbreviations: RMDQ, Roland Morris Disability Questionnaire; CI, confidence interval; FreBAQ, Fremantle Back Awareness Questionnaire; DASS-21, Depression Anxiety Stress Scale 21; PCS, Pain Catastrophizing Scale; PABQ-PA, Fear Avoidance Beliefs Questionnaire, physical activity subscale; BMI, body mass index.
      Standardized β coefficient represented expected change in SD units of logRMDQ for 1 SD change in independent variable.
      Table 6 shows the standardized β coefficients for linear regression models for pain intensity (NRS). Alone, FreBAQ explained 7.0% of the variance in pain intensity. The final model retaining FreBAQ and pain catastrophization explained 9.9% of the variance in pain intensity, of which FreBAQ uniquely contributed 3.6%, pain catastrophization uniquely contributed 2.7%, and 3.6% was shared between both variables. In the final model, an increase of 1 SD in FreBAQ was estimated to be associated with an increase in .20 SD of pain (NRS; 95% confidence interval, .07–.33; P = .007).
      Table 6Linear Regression Models for Pain Intensity (NRS, Scale of 0–10)
      UnivariableMultivariable 1Multivariable 2
      β (95% CI)
      Standardized β coefficient represented expected change in SD units of NRS for 1 SD change in independent variable.
      Pβ (95% CI)
      Standardized β coefficient represented expected change in SD units of NRS for 1 SD change in independent variable.
      Pβ (95% CI)
      Standardized β coefficient represented expected change in SD units of NRS for 1 SD change in independent variable.
      P
      Back perception (FreBAQ).26 (.14–.38)<.001.19 (.05–.32).007.20 (.07–.33).002
      Psychological distress (DASS-21).22 (.09–.34).001.05 (−.10 to .20).486
      Pain catastrophization (PCS).25 (.13–.37)<.001.15 (.01–.30).034.18 (.05–.30).007
      Fear avoidance (PABQ-PA).04 (−.07 to .16).547
      BMI.10 (−.02 to .23).111
      Lumbar pressure pain threshold−.10 (−.22 to .03).132
      Abbreviations: NRS, numeric rating scale; CI, confidence interval; FreBAQ, Fremantle Back Awareness Questionnaire; DASS-21, Depression Anxiety Stress Scale 21; PCS, Pain Catastrophizing Scale; PABQ-PA, Fear Avoidance Beliefs Questionnaire, physical activity subscale; BMI, body mass index.
      Standardized β coefficient represented expected change in SD units of NRS for 1 SD change in independent variable.

      Discussion

      One key aim of this study was to report on the initial testing of the updated FreBAQ in a large heterogeneous sample of people with CLBP and present the outcomes of a comprehensive evaluation of the scales’ psychometric properties using the Rasch model. The results of this analysis suggest that the scale functions well. The questionnaire appears unidimensional with no redundant items, has minimal ceiling and floor effects, and acceptable internal consistency, with a Cronbach α very close to that reported in the original development report.
      • Wand B.M.
      • James M.
      • Abbaszadeh S.
      • George P.J.
      • Formby P.M.
      • Smith A.J.
      • O’Connell N.E.
      Assessing self-perception in patients with chronic low back pain: Development of a back-specific body-perception questionnaire.
      The item hierarchy appeared to progress in a theoretically plausible fashion supporting the construct validity of the questionnaire. Furthermore, the differential item functioning analysis showed that none of the items were biased by demographic or clinical variables. However, the FreBAQ items were relatively difficult to endorse and are thus better suited to assessing those with comparatively more frequent episodes of perceptual impairment.
      Item 8 (My back feels like it has shrunk) functioned poorly in that it was significantly more difficult to endorse than the other items, did not fit the predicted hierarchal order, and showed misfit. This, however, was not unexpected because items 8 and 7 (My back feels like it has shrunk, My back feels like it is enlarged) relate to the perceived size of the back. Although it is plausible a respondent could experience either impairment at differing times, it is more likely they will experience one and not the other. The data support this notion with most respondents reporting frequent feelings of enlargement but not shrinkage. The comparatively few responses to item 8 accounted for the misfit and it being the most difficult item to endorse. That some respondents do experience feelings of shrinkage, however, suggests the item might be important for some and the minor statistical anomalies it creates do not warrant its exclusion.
      We noted that category 1 (Rarely) was underused by the sample, suggesting the respondents could not clearly discriminate between ‘rarely’ and ‘occasionally.’ Nonetheless, the scale behaved in the expected manner, with persons with more frequent perceptual impairments scoring higher on each item suggesting changes to the category structure of the scale are not necessary. Retaining the original category structure also has the advantage of enabling comparisons to be made with data already reported
      • Beales D.
      • Lutz A.
      • Thompson J.
      • Wand B.M.
      • O’Sullivan P.
      Disturbed body perception, reduced sleep, and kinesiophobia in subjects with pregnancy-related persistent lumbopelvic pain and moderate levels of disability: An exploratory study.
      • Wand B.M.
      • James M.
      • Abbaszadeh S.
      • George P.J.
      • Formby P.M.
      • Smith A.J.
      • O’Connell N.E.
      Assessing self-perception in patients with chronic low back pain: Development of a back-specific body-perception questionnaire.
      and ongoing studies which may use the scale.
      Overall, the sample used the FreBAQ as expected with only 9% of respondents displaying misfit. That misfitting persons were significantly older can be explained, in part, by their responses to item 8. Older persons found item 8 somewhat easier to endorse compared with younger persons suggesting older people experienced more frequent feeling of shrinkage, rather than expansion. Preferentially endorsing the rarely used item 8 over item 7 would result in person misfit. Future studies are needed to explain these differences but it is plausible that older people with relatively few perceptual impairments experience occasional specific impairments that are associated with age-related changes. Alternatively, they may have not understood the question or answered incorrectly. Nonetheless, that there were no overt patterns in the response strings in general suggests the FreBAQ items are not problematic.
      Another key aim was to explore the relationships between body perception, nociceptive sensitivity, distress, and beliefs about back pain. As hypothesized, disturbed perpetual awareness of the back correlated with distress, fear avoidant beliefs, and catastrophizing cognitions about pain. We also found that higher levels of disturbed self-perception were related to increased sensitivity to pressure at the low back but not cold or heat. This may represent the different tissues that are involved in testing because thermal sensitivity likely assesses sensitivity to stimulus delivered to superficial tissues whereas pressure sensitivity is thought to also assess sensitivity to stimuli delivered to deep tissue.
      • Graven-Nielsen T.
      • Mense S.
      • Arendt-Nielsen L.
      Painful and non-painful pressure sensations from human skeletal muscle.
      This is consistent with previous work, which has suggested that pressure pain thresholds are highly accurate in discriminating between people with CLBP and healthy control participants, whereas the discriminative ability of heat and cold pain sensitivity is limited.
      • Neziri A.Y.
      • Curatolo M.
      • Limacher A.
      • Nüesch E.
      • Radanov B.
      • Andersen O.K.
      • Arendt-Nielsen L.
      • Jüni P.
      Ranking of parameters of pain hypersensitivity according to their discriminative ability in chronic low back pain.
      The relationship found among these variables offers some preliminary support for the model hypothesized in Fig 1, which suggest these factors are likely mutually reinforcing.
      We also provide some evidence that disrupted perceptual awareness of the back significantly and uniquely contributes to pain intensity in this population. In our sample, disturbed body perception appears to be more strongly associated with pain intensity than psychological distress, fear avoidance beliefs, or an objective measure of lumbar spine sensitivity. It is plausible that changes in how the back feels to the individual can affect the pain experience, as our data suggest. Planning and coordination of movement requires an intact perception of the body and its position in space, and movement quality may be compromised if body perception is disrupted. Suboptimal movement patterns might abnormally load the back and contribute to nociceptive input and movement-related pain in those with CLBP.
      • Hodges P.W.
      • Smeets R.J.
      Interaction between pain, movement, and physical activity: short-term benefits, long-term consequences, and targets for treatment.
      • O’Sullivan P.
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      It has also been hypothesized that danger signals may arise centrally as a result of incongruence between predicted and actual sensory feedback associated with movement by virtue of disrupted body maps.
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      This mechanism might also contribute to the pain experience in people with CLBP whose perception of the back is degraded, although experimental support for this hypothesis is inconsistent.
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      It is also plausible that sensitivity might be enhanced by changes in body perception.
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      Role of distorted body image in pain.
      Pain emerges when we conclude our body to be under threat and in need of protection
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      so how the body is perceived should be seen as fundamental to the emergence of pain. In support of this idea are data that show that sensitivity to experimental pain is increased when perception of the body part is distorted by visual manipulation
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      and is partly endorsed by the correlations noted between lumbar pressure pain threshold and FreBAQ scores. Finally loss of sensory precision and decreased ability to accurately localize sensory input could enhance sensitivity by increasing the salience and threat value of any sensory information, noxious or otherwise, received from the affected area. Importantly, preliminary data suggest that strategies that likely improve self-perception such as mirror visual feedback
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      may decrease activity-related pain in people with CLBP.
      We also found that FreBAQ scores were uniquely associated with disability whereas measures of pain catastrophization, fear avoidance beliefs, and lumbar spine sensitivity were not. It is plausible that how the back is perceived may uniquely influence disability. Although numerous factors interact to determine the level of engagement in functional activities
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      the perception of the fitness, health, and robustness of the back might be factors that drive avoidance. Previous research has shown that people with high levels of LBP-related disability have a more pathoanatomical perspective on the cause of their back pain than those with low levels of disability,
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      Health literacy and beliefs among a community cohort with and without chronic low back pain.
      and qualitative research supports the notion that people with LBP perceive the back as fragile and easy to injure,
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      particularly in those with high levels of pain-related fear.
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      • Watkins R.
      • Schütze R.
      • O’Sullivan P.
      What do people who score highly on the Tampa Scale of Kinesiophobia really believe?: A mixed methods investigation in people with chronic nonspecific low back pain.
      Features captured in the FreBAQ such as feelings of disconnection from the back, finding the back difficult to control, and altered perception in the size and shape of the back might add to the belief that the back is fragile and not fit for function, which may contribute to avoidant behavior. Actual peripheral tissue health is also likely to contribute to the perception of fitness. Exploratory studies on healthy subjects have reported a body part-specific decrease in temperature
      • Moseley G.L.
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      within minutes of experimental body awareness disruption, suggesting a link between self-perception and homeostatic control. It is not clear whether such changes do lead to meaningful changes in tissue health but the possibility that altered body perception could also negatively influence actual peripheral tissue health is worthy of consideration.
      The findings presented should be considered in light of the limitations of the study. The sample is quite heterogeneous, being drawn from clinical and nonclinical settings so likely represents participants with very different treatment histories and may partly explain why the associations with clinical severity found in this study are weaker than we have previously noted with a sample drawn only from a clinical setting.
      • Wand B.M.
      • James M.
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      • Smith A.J.
      • O’Connell N.E.
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      Also, although we attempted to only recruit participants with nonspecific LBP, the tool used to exclude individuals with radicular pain may not have successfully screened out all these individuals. Although altered self-perception appears to be a feature of CLBP its importance in the development and persistence of CLBP remains uncertain. It should be considered that self-perception changes may simply be epiphenomena. We have taken a robust multivariate approach to assessing the unique relationships between self-perception and clinical features of CLBP. However, such approaches can only control for known and measured variables and it remains possible that observed relationships might be confounded by unknown variables. The cross-sectional nature of the study also precludes us from drawing any inferences of cause and effect. Finally, the contribution of self-perception to the variance seen in pain and disability is relatively small. Small effect sizes increase the chance that relationships observed may not be causal in nature. Further longitudinal and experimental studies are required to explore these issues.

      Conclusions

      The findings presented provide further evidence that body perception is disturbed in people with CLBP. The level of perceptual disturbance is positively correlated with pain intensity and disability. In this sample, disturbed body perception seems to make a more important contribution to severity of the clinical condition than commonly considered factors such as pain catastrophization, psychological distress, fear avoidance beliefs, and local tissue sensitivity. These findings suggest that assessment of body perception might be useful in helping clinicians understand the complexity of the LBP experience and could serve to guide management. The data presented show that the FreBAQ is a simple, feasible, and psychometrically sound method of assessing disruption of body image in people with CLBP.

      Acknowledgments

      The authors thank Associate Professor Helen Slater and Dr Darren Beales for their assistance with planning of the study.

      Supplementary Data

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