[The reliability and validity of a Croatian version of the Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) in patients with ankylosing spondylitis].

The aim of the study was to investigate the reliability and the validity of the Croatian version of the Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Disease Activity index (BASDAI) in patients with ankylosing spondylitis (AS). Patients with established diagnosis of AS participated in the study. Fifty-two and 48 patients were included for the evaluation of BASFI and BASDAI, respectively. For translation international translation steps were followed. For reliability patients recompleted both indices on the following day. To assess validity following parameters were obtained: spinal mobility in sagittal plane, chest expansion index, erythrocyte sedimentation rate, serum C-reactive protein, level of pain and patient's global health. Apart from descriptive statistics Spearman's rho coefficient was used. Correlation between BASFI and BASDAI score was 0.621. The mean BASFI scores on two occasions (within 24 hours) were 4.82 +/- 2.67 versus 4.88 +/- 2.52 (r = 0.961; p < 0.01), and for BASDAI scores were 5.46 +/- 2.30 versus 5.32 +/- 2.19, respectively (r = 0.959; p < 0.01). Stability index for both indices was 0.98. High correlation was found for each repeated question of BASFI and BASDAI. For both indices congruent validity demonstrated the best correlation with cervical and thoracic mobility. Also, the correlation was observed for BASFI with spinal mobility in lumbar region and with chest expansion index, and for BASDAI with the level of pain. Our findings indicate that Croatian version ofBASFI and BASDAI is reliable and valid. Therefore, it can be used in clinical research as well as in clinical practice.