Estimation of the Bath Ankylosing Spondylitis Disease Activity Index cutoff for perceived symptom relief in patients with spondyloarthropathies

Objective. To estimate the best Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) cutoff based on patients' perceptions of symptom relief collected in a large population of patients with spondyloarthropathies (SpA), in comparison to the BASDAI cutoff determined by experts. Methods. A survey of patient perceptions about current disease control was conducted among the members of Spondylis, one of the main not-for-profit SpA patient organizations in France. BASDAI was among data collected by the questionnaire. To estimate the best BASDAI cutoff for discriminating between poor and well perceived controlled groups, we plotted the receiver operating characteristic (ROC) curve. We also determined the cutoff separately in male and female patients. Results. Of the 1000 mailed questionnaires, 485 were returned without any missing data regarding perceived disease control and the BASDAI. Of these patients, 55.3% perceived inadequate control of their disease. The mean BASDAI in the overall population was 43.5 +/- 22.9, 30.4 +/- 19.9 in the well controlled group and 54 +/- 19.4 in the poorly controlled group (p < 0.001). The best BASDAI cutoff for discriminating between patients in the 2 groups was 39 (sensitivity 74.6% and specificity 72.4%). According to gender, the best cutoff was 44 for women and 36 for men. Conclusion. The best BASDAI cutoff of 39 based on patients' perceptions was very similar to that selected by international experts, i.e., 40. Gender affected the cutoff for perceived symptom relief in our study. These results need to be confirmed by further studies collecting the opinions of both patients and physicians.