Performance tests in people with chronic low back pain: responsiveness and minimal clinically important change.
STUDY DESIGN
Cohort study.


OBJECTIVE
To assess the responsiveness and minimal clinically important change (MCIC) of 6 commonly-used performance tests (5-minute walking, 50-ft walking, sit-to-stand, 1 minute stair climbing, loaded forward reach, Progressive Isoinertial Lifting Evaluation).


SUMMARY OF BACKGROUND DATA
Performance tests are used to evaluate physical function in people with low back pain. Little is known about their clinimetric properties.


METHODS
Performance tests were administered in people with chronic nonspecific low back pain (n = 198) before and after 10 weeks of treatment. At 10 weeks, the global perceived effect scale was used to determine if participants judged themselves as worsened, unchanged, or improved. The mean change scores for each performance test were calculated. A performance test was considered responsive if the area under the receiver operating characteristic curve (AUC) was equal to or greater than 0.70. We used 2 methods to evaluate MCIC: the optimal cut-off point based on the receiver operating characteristic curve, which takes into account both sensitivity and specificity, and the minimal detectable change for improvement, which considers test specificity only.


RESULTS
In general, the mean change scores were the smallest in participants who judged themselves worsened and largest in those reporting to be improved. Sit-to-stand (AUC = 0.75) and stair climbing (AUC = 0.72) were the only performance tests that showed adequate responsiveness. For sit-to-stand, the MCIC ranged from 4.1 to 9.8 seconds (19%-45% of the mean baseline score). For stair climbing, the MCIC ranged from 14.5 to 23.9 steps (19%-31% of the mean baseline score).


CONCLUSION
Only 2 of the 6 performance tests were responsive. Both had acceptable MCIC values. Developing individualized performance tests might partly overcome the general lack of responsiveness of performance tests. Future research should focus on the clinimetric testing of performance tests in subgroups.