Initial infliximab dose for patients positive and negative for antibodies toward infliximab (ATI
, respectively). Box plots show the medians and interquartile ranges, and the whisker plots represent the 95th percentiles. Two patients in the RA subgroup (open circles) received 5 mg/kg infliximab at initiation because they were initially suspected of having psoriatic arthritis. During follow-up, anticitrullinated protein antibodies were detected in both patients, which explains their placement in the RA subgroup. Two patients with SpA (open circles) received 3 mg/kg infliximab at initiation because they had a peripheral form of the disease and were therefore misclassified as having RA. ATI: antibodies toward infliximab; ATIpos: ATI detected at least once during follow-up; ATIneg: ATI not detected; RA: rheumatoid arthritis; SpA: spondyloarthritis.