High intraindividual week-to-week variability in BASDAI and BASFI values: Are several evaluations needed before starting or stopping TNFα antagonist therapy for spondyloarthropathies?

Abstract Objective To evaluate intraindividual variability of the BASDAI, BASFI, and HAQ in patients with spondyloarthropathies. Methods The three variables were collected prospectively in 24 patients, once a week for 30 weeks. They were also collected retrospectively in 31 patients on stable infliximab regimens with a mean of 11.5 ± 4 injections, starting at the fourth infusion. Results The BASDAI and BASFI showed high intraindividual variability from week to week; SDs greater than 1 were found for the BASDAI in 14/24 patients and for the BASFI in 10/24 patients, and ranges greater than 4/10 occurred for the BASDAI in 13/24 patients and for the BASFI in 10/24 patients. Although the mean BASDAI was greater than 4 in only 6/24 patients, values greater than 4 occurred on one or more occasions in 19 (79%) patients. The retrospective study of infliximab-treated patients from the fourth infusion onward also showed high variability of BASDAI and BASFI values, with SDs greater than 1 in 18/31 patients and ranges greater than 4 in 14/31 patients and greater than 2 in 22/31 patients. Conclusion Repeated determination of the BASDAI and BASFI by the patients (using paper forms or personal digital assessments) may help to identify candidates for treatment intensification, to optimize infliximab injection regimens in good responders, and to avoid unnecessary switching from one TNFα antagonist to another.