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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?

Oesch, Peter MSc*,†; Meyer, Kathrin MPH; Jansen, Beatrice MSc§; Mowinckel, Petter MSc; Bachmann, Stefan MD*,†,‡; Hagen, Kare Birger PhD‖,**

doi: 10.1097/BRS.0b013e31822e6088
Occupational Health/Ergonomics

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.

A cross-sectional study was performed to investigate the association of “nonorganic somatic components” together with physical and other psychosocial factors on functional capacity evaluation in patients with chronic nonspecific low back pain undergoing fitness-for-work evaluation. Nonorganic somatic components were consistent independent predictors for all functional capacity evaluation tests.

*Research Department, Rehabilitation Centre Valens, Switzerland

Department of Rheumatology, Rehabilitation Centre Valens, Switzerland

Department of Geriatrics, Inselspital, Bern University Hospital, Switzerland

§Department of Work Rehabilitation, Rehaklinik Bellikon, Bellikon, Switzerland

Division of Rheumatology and Institute of Physical Medicine, University Hospital Zurich, Switzerland

National Resource Centre for Rehabilitation in Rheumatology, Diakonhjemmet Hospital, Oslo, Norway

**Institute of Health and Society, Department of Health Sciences, University of Oslo, Norway

Address correspondence and reprint requests to Peter Oesch, MSc, Rheuma- und Rehabilitationszentrum Valens, 7317 Valens, Switzerland; E-mail: p.oesch@klinik-valens.ch

Acknowledgment date: April 22, 2011. First revision date: June 29, 2011. Acceptance date: July 6, 2011.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Verein IG Ergonomie SAR, Switzerland, funds were received to support this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Ethical approval was obtained from the 3 regional ethics committees (EKSG 08/029/2B; SPUK N°. 784, EKAG 08/058) where the rehabilitation clinics are located.

© 2012 Lippincott Williams & Wilkins, Inc.