Disease activity in rheumatoid arthritis patients stratified by hemoglobin levels: a multi-center study

Objectives: Hemoglobin (Hb) level and its relation to rheumatoid arthritis (RA) is multifactorial. The primary aim of this study was to examine the association between Hb levels and disease activity in patients with RA.

Methods: This retrospective study obtained data from adult RA patients with Hb reports from the Kuwait Registry for Rheumatic Diseases. Patients were recruited from four public hospitals in Kuwait between February 2013 and February 2022. The cohort was stratified into two groups: Hb ≤ 110 g/L and Hb > 110 g/L. Demographic, treatment, clinical, and laboratory characteristics were used to compare the two Hb groups. Multivariate and univariate statistical analyses were used to analyze the data.

Results: The total number of patients visited (Nv) was 11 393 and consecutive patients with RA diagnoses and Hb data (Np) were 1584. Both Nv and Np were included in the study. Of these, 72.5% (n = 8260) had high Hb levels and 27.5% (n = 3133) had low Hb levels. The average age of the cohort was 55.9 ± 12.5 years. Logistic regression analysis revealed that a greater number of non-Kuwaiti patients had anemia than Kuwaiti patients [adjusted odds ratio (aOR) = 1.34, 95% CI: 1.16-1.56; p < 0.001). Patients who received biologic treatment were more likely to be non-anemic [aOR = 1.33, 95% CI: 1.23-1.45; p < 0.001). Additionally, the study demonstrated that patients with anemia had greater odds of acquiring Disease Activity Score -28 joint count (DAS-28) ≥ 3.2 versus DAS-28 < 3.2 [aOR = 0.74, 95% CI: 0.61-0.90; p = 0.002].

Conclusions: Lower Hb levels in RA are an independent predictor of disease activity.