FRI0432 Comparison of tests for lumbar flexion and hip function in patients with axial spondyloarthritis and in healthy controls
Authors: C. Stolwijk, S. Ramiro, R. Landewé, D. van der Heijde, A. van Tubergen
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> Different approaches exist to assess limitation in spinal mobility and hip function in axial spondyloarthritis (axSpA). The 15cm-Schober's test (originally included in the Bath AS mobility index (BASMI)), and the 10cm-Schober's test (recommended by the ASAS to use in the BASMI), are both used to quantify lumbar flexion. The intermalleolar distance (IMD) is included in the BASMI for measuring hip function. A substitute for the IMD, the internal hip rotation (IHR) was later proposed, and is part of the Edmonton AS Metrology Index (EDASMI) [1]. However, direct comparisons between the different approaches are lacking. <h3>Objectives</h3> To assess the agreement between both the 10cm- and 15cm- Schober's test and the IMD and the IHR, and their performance in composite indices. <h3>Methods</h3> A cross-sectional study was conducted among both healthy volunteers (HVs) aged 20-69 years old ('Mobility study') stratified for gender, age- and height-categories, and consecutive outpatients with axSpA. The spinal and hip mobility tests were assessed in all subjects. Agreement between the 10cm- and 15cm-Schober's test and between the IMD and IHR were assessed by Pearson correlation coefficients, visually by cumulative probability plots, and by Bland-Altman plots. The performance of the two versions of the Schober's test in BASMI<sub>10</sub> was assessed by calculating the BASMI-score using either method. <h3>Results</h3> A total of 393 HVs (50.9% males; mean age 43.9 years) and 77 patients (50.6% males; mean age 47.9 years; 76.6% fulfilled the modified New-York criteria) were included. The 10cm- and 15m-Schober's test had a mean value of 5.0cm (SD 1.0) and 6.3cm (SD 1.2) in HVs, and 3.7cm (SD 1.5) and 5.2cm (SD 1.9) in patients, respectively. A strong correlation between the 10cm- and 15cm-Schober's test was found, both in HVs (r = 0.89) and in patients (r = 0.92). The Bland-Altman plot showed a systematic difference between the 15cm- and 10cm-Schober's test of 1.3cm (SD 0.5) in HVs and 1.5cm (SD 0.8) in patients. This difference resulted in an increased mean total BASMI<sub>10</sub> score of 0.3 points in HVs and 0.4 points in patients with the 15cm-Schober compared with the 10cm-Schober. The IMD had a mean value of 112cm (SD 14) in HVs and 100cm (SD 20) in patients. The IHR had a mean value of 48cm (SD 10) in HVs and 45cm (SD 10) in patients. The correlation between the IMD and IHR was weak both in HVs (r = 0.29) and in patients (r = 0.37). A wide distribution of scores and no tendency for parallel increases between the IMD and IHR was found. <h3>Conclusions</h3> The 10cm- and 15cm-Schober's test are highly correlated but the 15cm-method results in systematically higher scores than the 10cm-method, which influences the total BASMI score. Therefore, these methods cannot be used interchangeably. The IMD and IHR are not correlated; the IHR cannot be used as a substitute for the IMD. <h3>References</h3> Maksymowych et al. A&amp;R 2006;55:575-82 <h3>Disclosure of Interest</h3> None Declared