New opportunities for dynamic evaluation of systemic inflammatory response in patients with rheumatoid arthritis

Systemic inflammation in rheumatoid arthritis (RA) is associated with changes in both counts and composition of circulating inflammatory blood cells such as neutrophils and lymphocytes. Accurate monitoring of inflammation grade and disease status in patients with RA is important in the inpatient setting. Purpose of the study was to determine inflammatory indices derived from the general blood counts (GBC) in patients with active RA during inpatient treatment, and to search for association of these indices with clinical and laboratory parameters of the disease. The inflammatory indices (NLR, neutrophil-to-lymphocyte ratio; MLR, monocyte-to-lymphocyte ratio; PLR, platelet-to-lymphocyte ratio; SII – systemic immune inflammation index, SIRI, systemic inflammatory response index) were determined as based on the results of GBC performed using automated hematology analyzers in 43 patients with RA (55.8% males; aged 22 to 78 years; 88% with high disease activity) twice (at admission to hospitalization and at discharge). The average length of hospitalization was 14 [9;14] days. Common inflammatory markers (ESR and CRP) correlated with each other (r_s = 0.64), i.e., we have found correlations between CRP and leukocyte counts (r_s = 0.47), with PLR (r_s = 0.43), and age of patients (r_s = 0.34), as well as correlations of ESR with PLR (r_s = 0.37) and age of RA patients (r_s = 0.33). The SII index correlated strongly with NLR (r_s = 0.85) and PLR (r_s = 0.86), moderately with MLR (r_s = 0.49), but not with SIRI (p > 0.05). The SIRI index showed a correlation with DAS-28 degree (β = -0.072, p = 0.008). Markers obtained from GBC were not associated with age or sex of the examined individuals (except of SIRI, p = 0.027), no intergroup differences in the studied hematologic markers were found when classifying RA patients by the content of antibodies to cyclic citrullinated peptide, presence of erosions and systemic manifestations (except of PLR, p = 0.048). Only CRP and systemic immune inflammation index (SII) showed a significant decrease (p = 0.24 and p = 0.43, respectively) during hospitalization of patients with RA. No advantage was found for usage of two-component indices (NLR, MLR, PLR) as plausible tools, both for assessing inflammatory status and for management of patients with highly active RA. The SII index, combining the prognostic value of three parameters (platelets, neutrophils and lymphocytes), may be considered not only more powerful for predicting inflammation than single- or two-component hematologic markers, but also a valuable tool for monitoring inflammation and RA progression. Thus, the SII index (along with CRP) may be considered a potential biomarker for determining the outcome of inpatient treatment of patients with highly active RA.