RESULTS
Population:
One hundred thirty-seven patients (37 with RA, 53 with SpA and 47 with CD) treated by TNF alpha blockers (IFX=68, ADA=69) were included in the study. Table 1 illustrates the baseline clinical characteristics and disease activity scores of our patients.
Treatment characteristics of our patients including the type of TNF alpha blockers, the treatment duration and the combined treatment are summarized in table 2.
Prevalence of ADAbs and relation with drug levels
ADAbs were detected in 44 patients: 27 treated with IFX (40%) and 17 receiving ADA (25%) (p=0.195). ADAbs were positive among 13 RA patients (35%), 21 SpA patients (39%) and 10 CD patients (21%) (p=0.354) (table 3). The presence of ADAbs was inversely correlated to the trough levels of IFX and ADA during RA (p=0.01 and p<0.0001) (figure 1), SpA (p<0.01 and p<0.0001) (figure 2) and CD (p=0.001 and p=0.04) (figure 3).
Comparison of patients’ characteristics between ADAbs+ and ADAbs– patients:
Table 4 illustrates the comparison between ADAbs+ and ADAbs- patients. Demographic data including age, sex, disease duration, age at disease beginning were not statically different between the 2 groups, except for BMI. Indeed, RA ADAbs+ patients had higher BMI than ADAbs- ones (p=0.04). Concerning the concomitant drug used, there was not any significant association between AZA and immunogenicity. However, the use of MTX was significantly associated with immunogenicity in CD (p=0.04), with a dose effect in RA and CD (p=0.04 and p=0.005 respectively).
Comparison of disease activity between ADAbs + and ADAbs – patients
Laboratory and clinical data related to disease activity was not significantly different between ADAbs+ and ADAbs- patients (Table 5).
Safety
3 patients had infusion reactions to IFX. These 3 patients were ADAbs+ (p=0.01) and had lower trough levels of IFX (p<0.001).