Correlation of Hematological Indices and Acute-Phase Reactants in Rheumatoid Arthritis Patients on Disease-Modifying Antirheumatic Drugs: A Retrospective Cohort Analysis

Abstract

Acute-phase markers are often used to evaluate the disease activity of rheumatoid arthritis (RA). Occasionally, the serum levels of acute-phase reactants remain normal in patients with obvious inflamed joints. Hematological indices derived from complete blood counts have been shown to correlate with disease activity. This provides a potential practical implementation in daily practice. Only a few studies have evaluated the relation between hematological indices and novel RA treatment (i.e., biological and targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs); no research has examined the changes in hematological indices in RA treatments longitudinally. We conducted a retrospective study involving 273 RA patients with b/tsDMARD treatment and followed them for at least a year. Baseline, 3-month, and 6-month lab data were collected. The results indicated a reduction in the neutrophil–lymphocyte ratio (NLR), platelet–lymphocyte ratio (PLR), monocyte–lymphocyte ratio (MLR), and systemic immune-inflammation index (SII) post-treatment. Higher baseline PLRs and SIIs were associated with a more significant reduction in ESR at three months (η2 = 0.03/0.13, p = 0.21/0.023). NLR and SII correlated with CRP moderately at three months (r = 0.373/0.394, p < 0.001/< 0.001). A correlation comparison showed that the correlation of NLR and PLR with CRP differs during different periods (p = 0.037/0.004). Subgroup analysis revealed that the time effect on correlation is related to treatment with Janus kinase inhibitor and anti-interleukin-6 but not antitumor necrosis factors.