Development and Validation of a Pain Behavior Assessment in Patients with Chronic Low Back Pain.

PURPOSE: High levels of pain behavior adversely affect the success of multidisciplinary rehabilitation of patients with chronic nonspecific low back pain (CNSLBP). Functional capacity evaluation (FCE) assessment should detect high levels of pain behavior to prevent the inclusion of unsuitable patients to functional rehabilitation programs. The aim of this study was to develop a Pain Behavior Assessment (PBA) and to evaluate its construct validity. METHODS: The PBA was developed by experts in the field and is literature-based. Inclusion criteria for participants of the validation study were: CNSLBP, age 20-60 years, referral for fitness-for-work evaluation. The PBA was applied by physiotherapists during FCE. Rasch analysis was performed to evaluate the construct validity of the PBA. Internal consistency was indicated by the person separation index (PSI), which corresponds to Cronbach's alpha. RESULTS: 145 male (72.5%) and 55 female patients were included. Rasch analysis removed 11 items due to misfit and redundancy, resulting in a final PBA of 41 items. Item mean fit residual was -0.33 (SD 1.06) and total item Chi square 100.39 (df = 82, p = 0.08). The PSI value was 0.83. DIF analysis for age and gender revealed no bias. CONCLUSIONS: The PBA is a valid assessment tool to describe pain behavior in CNSLBP patients. The high PSI-value justifies the use of the PBA in individuals. The PBA may help to screen patients for high levels of pain behavior.

Functional Capacity Evaluation: Performance of Patients with Chronic Non-specific Low Back Pain Without Waddell Signs.

PURPOSE: The primary objective of this study is to evaluate the effect of Waddell signs (WS) on Functional Capacity Evaluation (FCE) in patients with chronic non-specific low back pain (CNSLBP) undergoing fitness for work evaluation. If an effect is observed, the secondary objective is to report performance of patients without WS in a standardized 1 day FCE protocol. METHODS: Survey of patients with CNSLBP as their primary complaint, referred for fitness for work evaluation, age between 20 and 60 years. Main outcome measures were WS and performance during manual handling assessed with lifting from floor to waist, waist to crown, horizontal and one handed carry; grip strength with Jamar hand held Dynamometer; ambulation with stair climbing and six minute walking test; work postures with elevated work, forward bend standing, kneeling, and sitting. RESULTS: 145 male with a mean age of 44.5 years (±10.1), and 53 females with a mean age of 43.6 years (±11.0) were included. Mean days off work were in male 658 (±1,056) and in female 642 (±886). 33% of all patients presented positive WS. FCE performance in male and female patients with positive and negative WS differed significantly in all comparisons except grip strength of the dominant hand and sitting in female. Performance of patients with negative WS indicated a mean physical capacity corresponding to lightmedium work in females and medium work in males for both age groups. CONCLUSIONS: WS should be assessed for interpretation of FCE results. Despite long work absence, patients with CNSLBP with negative WS demonstrated a physical capacity corresponding to substantial physical work demands.

What is the role of "nonorganic somatic components" in functional capacity evaluations in patients with chronic nonspecific low back pain undergoing fitness for work evaluation?

STUDY DESIGN: Analytical cross-sectional study. OBJECTIVE: To assess the association of "nonorganic somatic components" together with physical and other psychosocial factors on functional capacity evaluation (FCE) in patients with chronic nonspecific low back pain (NSLBP) undergoing fitness-for-work evaluation. SUMMARY OF BACKGROUND DATA: Functional capacity evaluation is increasingly used for physical fitness-for-work evaluation in patients with chronic NSLBP, but results seem to be influenced by physical as well as psychosocial factors. The influence of nonorganic somatic components together with physical and other psychosocial factors on FCE performance has not yet been investigated. METHODS: One hundred twenty-six patients with chronic NSLBP referred for physical fitness-for-work evaluation were included. The 4 FCE tests were lifting from floor to waist, forward bend standing, grip strength, and 6-minute walking. Nonorganic somatic components were assessed with the 8 nonorganic somatic signs as defined by Waddell and were adjusted for age, sex, days off work, salary in the previous occupation, pain intensity, fear avoidance belief, and perceived functional ability in multivariate regression analyses. RESULTS: Between 42% and 58% of the variation in the FCE tests was explained in the final multivariate regression models. Nonorganic somatic components were consistent independent predictors for all tests. Their influence was most important on forward bend standing and walking distance, and less on grip strength and lifting performance. The physical factors of age and/or sex were strongly associated with grip strength and lifting, less with walking distance, and not at all with forward bend standing. The influence of at least 1 other psychosocial factor was observed in all FCE tests, having the highest proportion in the 6-minute walking test. CONCLUSION: Nonorganic somatic components seem to be consistent independent predictors in FCE testing and should be considered for interpretation of test results.