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Study Design: Cross-sectional study., Objective: To examine reference data for the Pain Disability Index (PDI) in Dutch and Canadian patient samples with a variety of musculoskeletal pain disorders and to test which potential factors are independently associated with the PDI score., Summary of Background Data: The PDI is a widely used generic instrument for measuring disability related to pain. It is unknown whether patients with spinal and other musculoskeletal diagnoses have different levels of disability when scored on the PDI., Methods: Patients were referred to secondary and tertiary care centers in the Netherlands and Alberta, Canada, between 2009 and 2013. All patients filled out a baseline questionnaire including demographics and the PDI. After first consultation with a medical doctor, diagnoses were set by the medical specialist. Univariate general linear models were used to examine correlations between PDI scores and age, sex, country of residence, diagnosis, and work status., Results: In total 6997 patients were included in this study: 1302 Canadian and 5695 Dutch patients. Mean PDI score of the total group was 37.8 ± 14.2. Reference values are presented and clustered into the following diagnostic groups: spinal nerve and intervertebral disc disorders; nonspecific back pain; rheumatic soft-tissue pain (widespread pain or fibromyalgia); spinal stenosis; and whiplash-associated disorder. The PDI score was significantly and relevantly associated with pain intensity (η explained variance from 20% to 25%), but not relevantly associated with age, sex, country of residence, and diagnostic group (η<3%). In the working subgroup, adding "current sick leave" as covariate increased the explained variance to 34%., Conclusion: Reference values of the PDI are presented. Patient ratings of disability on the PDI are relevantly associated with pain intensity and work status, but not with nationality or diagnostic group. Only minimal differences were identified between the various musculoskeletal diagnoses included., Level of Evidence: N/A.

Study Design: A cross-sectional study design was performed., Objective: To validate the pain disability index (PDI) extensively in 3 groups of patients with musculoskeletal pain., Summary of Background Data: The PDI is a widely used and studied instrument for disability related to various pain syndromes, although there is conflicting evidence concerning factor structure, test-retest reliability, and missing items. Additionally, an official translation of the Dutch language version has never been performed., Methods: For reliability, internal consistency, factor structure, test-retest reliability and measurement error were calculated. Validity was tested with hypothesized correlations with pain intensity, kinesiophobia, Rand-36 subscales, Depression, Roland-Morris Disability Questionnaire, Quality of Life, and Work Status. Structural validity was tested with independent backward translation and approval from the original authors., Results: One hundred seventy-eight patients with acute back pain, 425 patients with chronic low back pain and 365 with widespread pain were included. Internal consistency of the PDI was good. One factor was identified with factor analyses. Test-retest reliability was good for the PDI (intraclass correlation coefficient, 0.76). Standard error of measurement was 6.5 points and smallest detectable change was 17.9 points. Little correlations between the PDI were observed with kinesiophobia and depression, fair correlations with pain intensity, work status, and vitality and moderate correlations with the Rand-36 subscales and the Roland-Morris Disability Questionnaire., Conclusion: The PDI-Dutch language version is internally consistent as a 1-factor structure, and test-retest reliable. Missing items seem high in sexual and professional items. Using the PDI as a 2-factor questionnaire has no additional value and is unreliable.

Objective: To describe the comparison of multiple and single pain ratings in patients with complex regional pain syndrome type I (CRPS I)., Design: Correlation, agreement, and reliability analyses were performed between the average pain intensity measured 3 times a day over a course of 4 days and one single pain rating (designated the "recalled average" pain, as assessed by the patient) before treatment and at 1-, 3-, and 6-month periods after treatment., Patients: The patient population consisted of 54 patients with CRPS I in a randomized trial., Results: The results show that both measurements correlate and have excellent agreement. Furthermore, both ratings measure significant pain reduction after treatment; "recalled average" pain, however, reflects greater change in pain intensity., Conclusions: In patients with CRPS I a single pain rating is an accurate predictor of the average pain measured by a multiple pain-rating test. Moreover, both assessments are accurate enough to determine changes in pain over time with an effective treatment.

Background: Activities and their importance for daily living vary widely between patients. Patient-specific measurement of functional status means that the evaluation is focused on activities that an individual patient selected as main complaints., Objective: To develop and to evaluate a patient-specific approach for measuring functional status in low back pain., Study Design: A cohort of 150 patients was measured at baseline and 12 weeks later., Methods: The feasibility of the patient-specific approach was evaluated in patients with nonspecific low back pain. We used effect size statistics to evaluate responsiveness in terms of sensitivity to change and specificity to change., Results: The selection procedure for the main complaint was feasible but labor intensive. The patient-specific approach was able to detect changes in complaints that were highly relevant for the patients. The patient-specific approach appeared to be more sensitive to change but less specific to change compared with other instruments., Conclusions: On the basis of this study it would be valuable to apply the patient-specific approach in future studies, also with the aim of further evaluation. In the meantime a number of practical problems of the method need to be resolved.

Study Design: This study was a literature review of the quality of four disease-specific functional status questionnaires for patients with low back pain: Oswestry; Million; Roland; and Waddell disability questionnaire., Objectives: The questionnaires were evaluated in terms of general description, scale structure, reliability, validity, responsiveness, and clinical research applications., Summary of Background Data: Functional status is an outcome of great interest for clinical trials of low back pain., Methods: A computer-aided search was conducted of articles published between 1981 and 1993 and references given in selected relevant publications. Articles were selected if at least one of the four functional status questionnaires was used or if the authors gave relevant information about the methodology of these questionnaires., Results: There was not enough information available about the criteria of item selection used for the development of the questionnaires. The test-retest reproducibility of the questionnaires seemed satisfactory. The Oswestry and Roland disability questionnaires have been used and evaluated more frequently than the Million and Waddell. Therefore, we can be more certain about the validity and responsiveness of the former pair of questionnaires., Conclusion: In the absence of a gold standard, direct comparisons of evaluative functional status questionnaires in a single patient group are needed. Through direct comparisons, comparative validity and responsiveness can be assessed. Functional status measures are not currently used in many settings in which they would be valuable. It is important to encourage their wider use in clinical trials. Additional research is needed to compare and improve the existing questionnaires.