Schober test is not a valid assessment tool for lumbar mobility

The Schober test is considered reliable in evaluating lumbar mobility and its impairment. Especially in patients with chronic low back pain (cLBP) identification of functional restriction is important. We aimed to investigate whether the 5 cm Schober cut-off provides a valid distinction between unrestricted and restricted mobility in participants with and without cLBP (18–65 years). cLBP is defined as LBP persisting for ≥ 12 weeks. We analyzed agreement between the Schober test with two measurement devices (Epionics SPINE ® ; Idiag M360 ® ) and the influence of lumbar lordosis (LL) on their agreement. Also, the sensitivity and specificity of the Schober test was evaluated. For 187 participants (49.6%) Epionics SPINE ® RoF and Schober test matched (either ≥ 5 cm; > 40.8° RoF or ≤ 5 cm; < 40.8° RoF), for 190 participants (50.4%) the two measurements did not. Idiag M360 ® RoF of 190 participants (50.4%) showed corresponding results (either ≥ 5 cm; > 46.0° RoF or ≤ 5 cm; < 46.0° RoF). Non-agreement was seen in 187 participants (49.6%). LL differed significantly in the Epionics SPINE ® cohort (p < 0.001). Regarding the Epionics SPINE ® cohort, Schober test showed a sensitivity of 79.6% with a specificity of 36.1%. For the Idiag M360 ® cohort, Schober test showed a sensitivity of 68.2% and a specificity of 46.6%. Our results do not establish a consistent matching between Schober test and the device measurements. Therefore, Schober test may not be valid to predict impairment of lumbar mobility. We recommend Schober test as an add-on in monitoring of an individual relative to its case.