Background: The difficult access to thiopurine metabolites therapeutic drug monitoring led to the search for accessible markers to estimate thiopurine's efficacy. The difference in mean corpuscular volume (ΔMCV) ≥7fL at week 26 of azathioprine monotherapy (Aza) or combined with infliximab (AzaI) was shown to be associated with favourable outcomes in Inflammatory Bowel Disease (IBD). Objective: To confirm the association of ΔMCV ≥7 at week 26–28 with favourable outcomes in IBD in a Portuguese population.
Methods: Retrospective assessment of patients with IBD under Aza or AzaI at time-point: Week 26–28 of treatment. Demographic characterization and severity of pre-treatment disease was evaluated (location, previous surgery status, Mayo score and Crohn's disease activity index [CDAI]). Quantification of ΔMCV and association with time-point outcomes: Steroid-free clinical remission (Rem-sf, CDAI <150, Mayo <2); mucosal healing (MH); C-reactive protein (CRP) normalization <5. Patients with vitamin B12 deficiency were not included. Statistic: Chi-square test or Fisher exact test.
Results: A total of 122 patients with IBD were evaluated [(71 Crohn's disease, 28% operated); 57.4% women; mean age 40±15.6 years] at week 26–28 of treatment with Aza (86.9%) or AzaI (13.1%).
In both treatment groups the mean ΔMCV was ≥7 (Aza 7.9 vs. AzaI 8.1) and this was achieved in the same proportion of patients (66 vs. 62.5%). There was a strong association between ΔMCV ≥7 and remission outcomes (Rem-sf: p<0.05; CDAI <150/Mayo<2: p<0.001) and MH (p<0.05), but not with CRP normalization. However, CRP ≤10 was related to remission outcomes (Rem-sC: p<0.05; CDAI <150/Mayo <2: p<0.001) and MH (p=0.004).
Conclusions: This work confirmed the prognostic importance of ΔMCV ≥7 in our population. The correlation of ΔMCV ≥7 with clinical remission and mucosal healing outcomes occurred in Crohn's disease and Ulcerative Colitis and was independent of the anti-TNF association.