Mean corpuscular volume and red cell distribution width as predictors of methotrexate response in RA patients

To correlate ΔRDW and ΔVCM (baseline and week 12) with the number of patients achieving remission or low disease activity by CDAI at week 24 after initiating MTX.

Retro-prospective, analytical, and observational study in consecutive adult patients diagnosed with RA (ACR/EULAR 2010). Demographic data, clinical characteristics, personal history, initiated treatments, and VCM (fL) and RDW (%) at weeks 0, 4, 12, and 24 were evaluated. Safety data was recorded.

descriptive analysis, Chi² test or Fisher's exact test; Student's T-test or Mann-Whitney; and ANOVA or Kruskal-Wallis. Lineal and/or multiple logistic regression.

139 patients were included, of whom 109 completed the study requirements. 83.5% were women, median age (m) 50 years (IQR 39-60), with a median disease duration of 12 months (IQR 0-78). In the per-protocol analysis of 109 patients, the m ΔRDW between baseline and week 12 was 0.8 (IQR 0-2.4), and the m ΔVCM was 2.0 (IQR 0.1-4.4). No correlation was found between ΔRDW and CDAI at week 24 (Rho=-0.08; p=0.416), but a statistically significant correlation was found between ΔVCM and CDAI at week 24 (Rho=-0.190; p=0.048). Results were analyzed by intention to treat for 139 patients. Between baseline and week 12, a m ΔRDW of 0.8 (IQR 0-2.4) and a m ΔVCM of 2.2 (IQR 0.2-4.5) were recorded. No correlation was found between ΔRDW and CDAI at week 24 (Rho=-0.073; p=0.433), but a statistically significant correlation was found between ΔVCM and CDAI at week 24 (Rho=-0.217; p=0.018). 64.2%, 39.4%, and 15.6% of patients achieved CDAI 50/70/85 responses at week 12, respectively, with no significant changes at week 24. Univariate and multivariate analysis identified that the only factor significantly associated with achieving CDAI 50 at week 24 was achieving such a response at week 12 (p=0.001). Safety evaluation showed that 68 patients (48.9%) experienced adverse events, with 20 events (14.4%) related to MTX. Only 5 (3.6%) were considered serious adverse events, all of them unrelated to treatment.

This study revealed that an increase in red cell distribution width (RDW) and mean corpuscular volume (VCM) was associated with the initiation of MTX treatment. However, only a significant correlation was found between the change in VCM and RA activity measured by CDAI at week 24. Although ΔRDW did not show a significant association with RA activity, ΔVCM negatively correlated with CDAI at week 24. Additionally, a significant percentage of patients achieved a positive response at week 12, but there were no significant changes at week 24. Safety analysis showed that some patients experienced adverse events, with a small proportion considered serious adverse events not related to treatment. Overall, these findings suggest the importance of monitoring changes in VCM and considering its relationship with RA activity during MTX treatment.