Inter-examiner reproducibility of tests for lumbar motor control

Background: Many studies show a relation between reduced lumbar motor control (LMC) and low back pain (LBP). However, test circumstances vary and during test performance, subjects may change position. In other words, the reliability - i.e. reproducibility and validity - of tests for LMC should be based on quantitative data. This has not been considered before. The aim was to analyse the reproducibility of five different quantitative tests for LMC commonly used in daily clinical practice. Methods: The five tests for LMC were: repositioning (RPS), sitting forward lean (SFL), sitting knee extension (SKE), and bent knee fall out (BKFO), all measured in cm, and leg lowering (LL), measured in mm Hg. A total of 40 subjects (14 males, 26 females) 25 with and 15 without LBP, with a mean age of 46.5 years (SD 14.8), were examined independently and in random order by two examiners on the same day. LBP subjects were recruited from three physiotherapy clinics with a connection to the clinic's gym or back-school. Non-LBP subjects were recruited from the clinic's staff acquaintances, and from patients without LBP. Results: The means and standard deviations for each of the tests were 0.36 (0.27) cm for RPS, 1.01 (0.62) cm for SFL, 0.40 (0.29) cm for SKE, 1.07 (0.52) cm for BKFO, and 32.9 (7.1) mm Hg for LL. All five tests for LMC had reproducibility with the following ICCs: 0.90 for RPS, 0.96 for SFL, 0.96 for SKE, 0.94 for BKFO, and 0.98 for LL. Bland and Altman plots showed that most of the differences between examiners A and B were less than 0.20 cm. Conclusion: These five tests for LMC displayed excellent reproducibility. However, the diagnostic accuracy of these tests needs to be addressed in larger cohorts of subjects, establishing values for the normal population. Also cut-points between subjects with and without LBP must be determined, taking into account age, level of activity, degree of impairment and participation in sports. Whether reproducibility of these tests is as good in daily clinical practice when used by untrained examiners also needs to be examined.