Data collection
Data collection was carried out before the initiation of the biologic, at the same time of blood samples collection and 6 months later. It concerned:
-Demographics: age, sex, body mass index (BMI)
-Disease activity information’s: erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), the diseased activity score in 28 joints (DAS28) for RA patients [19], the bath ankylosing spondylitis disease activity index (BASDAI) [10] and the ankylosing spondylitis disease activity score (ASDAS) [11] for SpA patients and the Harvey Bradshaw index (HBI) [12] for CD patients.
We divided patients into responders and non-responders. For RA patients, DAS28 < 2.6 means remission, DAS28 between 2.6 and 3.2 means low disease activity, DAS28 between 3.2 and 5.1 means moderate activity and DAS 28 > 5.1 means high activity [9]. Patients in remission or low disease activity were considered as responders, and others as non-responders.
For SpA patients, ASDAS (calculated with CRP) < 1.3 means inactive disease, ASDAS between 1.3 and 2.1 means moderate disease activity, ASDAS between 2.1 and 3.5 means high disease activity and ASDAS > 3.5 means very high disease activity [11]. Patients with inactive disease or moderate disease activity were considered as responders, and others as non-responders.
For CD patients, responders were those whom HBI decreased to 4 points or less or by 3 points or less from baseline [12].
-Data related to the treatment: the type of TNF alpha blocker, duration of intake, levels and frequency of intake and concomitant use of conventional synthetic disease modifying anti rheumatic drugs (csDMARDs).