Comparison of Tests for Lumbar Flexion and Hip Function in Patients With and Without Axial Spondyloarthritis

Objectives: To compare the 15cm- with the 10cm-Schober's test, and the intermalleolar distance (IMD) with the internal hip rotation (IHR). Methods: A cross-sectional study was conducted among both normal individuals and patients with axial spondyloarthritis (axSpA).The spinal and hip mobility tests were assessed in all subjects. Agreement between the different tests was assessed with correlation coefficients, Bland and Altman agreement, and by cumulative-probability-plots. The component scores for lumbar flexion in the Bath Ankylosing Spondylitis Metrology Index (BASMI) with use of either the 10cm-Schober's test or the 15cm-Schober's test were compared. Results: A total of 393 normal individuals (51% males; mean age 44 years) and 90 patients with axSpA (53% males; mean age 49 years) were included. A strong correlation was found between the 10cm- and 15cm-Schober's test, both in normal individuals (r = 0.89) and in patients (r = 0.93). The 10cm-Schober's test was systematically lower than the 15cm-test with an average difference of 1.5cm (SD 0.8) in patients, resulting in a higher total BASMI score of 0.4 (SD 0.2) points. The correlation between IMD and IRH was weak, both in normal individuals (r = 0.29) and in patients (r = 0.40). Conclusion: The 10cm- and 15cm-Schober's tests are highly correlated but, as expected, the 10cm-method is systematically lower than the 15cm-method. Therefore, these measures cannot be interchangeably used in the BASMI. The IMD and IHR are not correlated, indicating that they measure different aspects of hip mobility. Therefore, the IHR cannot be used as a substitute for the IMD. (c) 2014 American College of Rheumatology.