The prognostic value of functional capacity evaluation in patients with chronic low back pain: part 1: timely return to work.
METHODS
Historical cohort study.


OBJECTIVE
We examined the validity of the Isernhagen Work Systems' Evaluation in predicting timely return to work.


BACKGROUND
Functional Capacity Evaluations are used commonly to determine readiness for return to work, yet little is known of their validity.


METHODS
Workers' compensation claimants undergoing Functional Capacity Evaluations following work-related low back injury were studied. Two cohorts were formed, one on which exploratory analyses were conducted and a second for confirmation. Evaluation indicators were the number of tasks in the protocol rated as failed and performance during the floor-to-waist lift task. The primary outcome investigated was time receiving total temporary disability benefits (as a surrogate of return to work) and a secondary outcome was time until claim closure in the year following Evaluation. Cox proportional-hazards regression was used to determine the prognostic effect of Evaluation crudely and after controlling for potential confounders.


RESULTS
Few patients (4%) were found to pass all Evaluation tasks, yet most experienced total temporary disability suspension and claim closure within 1 year following Functional Capacity Evaluations. Better Evaluation performance was related to faster time to suspension of total temporary disability benefits and claim closure after controlling confounding factors, but explained little of the variation in these outcomes (approximately 10%). Performance on the floor-to-waist lift was as predictive as the number of failed tasks in the entire Functional Capacity Evaluations protocol.


CONCLUSIONS
Better performance on Evaluation was weakly associated with faster recovery; however, the amount of variation explained was small. One task in the Evaluation was as predictive as the entire protocol.
Gross
Douglas P
DP
Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada. dgross@ualberta.ca
Battié
Michele C
MC
Cassidy
J David
JD
D000328:Adult; D019567:Back Injuries / Q000150:complications; D002170:Canada; D002908:Chronic Disease; D015331:Cohort Studies; D004185:Disability Evaluation; D004651:Employment / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D017770:Lifting; D017116:Low Back Pain / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D011237:Predictive Value of Tests; D011379:Prognosis; D020127:Recovery of Function; D015203:Reproducibility of Results; D018582:Sick Leave / Q000706:statistics & numerical data; D013997:Time Factors