Do patients with ankylosing spondylitis adapt to their disease? Evidence from a ‘then-test’ in patients treated with TNF inhibitors

OBJECTIVE: To investigate whether patients with ankylosing spondylitis (AS) adapt to their disease, using the ‘then-test’. METHODS: Data from patients participating in the AS Study for Evaluation of Recombinant Infliximab Therapy (ASSERT) and continuing in the European AS Infliximab Cohort (EASIC) were used. At 5 assessments in EASIC, patients were asked to rerate their global well-being before the start of infliximab in ASSERT. The patients evaluated their past situation by using a ‘then-test’ (‘retrospective patient global’). Initial and retrospective patient global were compared using a paired t test, and mixed linear models investigated whether the retrospective score of well-being was stable at all follow-up assessments in EASIC. Linear regression analysis explored whether treatment response was associated with the difference between the initial and retrospective score (‘gap’) while adjusting for possible confounders. RESULTS: 86 patients (mean age 39.8 years (SD=10.4), mean disease duration 10.8 years (SD=8.5)) contributed to the current analyses. At the time of starting infliximab, patients judged their global at 7.0 (SD=1.6), and with the ‘then-test’ at 7.2 (SD=2.3) (p=0.45). Time elapsed did not influence the ‘then-test’ (p=0.13). Multivariably, the gap was irrespective of treatment response, but associated with initial patient global (p<0.01) and initial Bath AS Disease Activity Index (p=0.02). CONCLUSIONS: Patients with AS accurately judged their global well-being before starting treatment with tumour necrosis factor inhibition, even though substantial time had elapsed. The difference between initial and retrospective judgment was irrespective of treatment response. In this setting, the ‘then-test’ could not prove adaptation in AS. TRIAL REGISTRATION NUMBER: NCT01286545.