The Role of NLR, PLR, SII and CRP Pre- and Post-Treatment with Infliximab in Rheumatoid Arthritis

<b>Background</b>: Inflammatory activity in rheumatoid arthritis can be determined by normal blood count ratios such as Neutrophil Lymphocyte Ratio (NLR), Platelet Lymphocyte Ratio (PLR), Systemic Immune Inflammation Index (SII), and C-reactive Protein (CRP). <b>Objective</b>: The aim of this research is to determine how these markers change after therapy and whether their pre- and post-treatment differences follow patterns that allow for simple parametric analyses. <b>Methods</b>: A prospective cohort of 52 RA patients (30 females and 22 males) was examined. The patients' blood samples were tested at baseline and at the end of their 6-month Infliximab treatment. Hematologic markers such as NLR, PLR, and SII were calculated from the complete blood count (CBC), and CRP levels were measured. The statistical methods of Shapiro-Wilk (SW), Kolmogorov-Smirnov (KS), and Anderson-Darling (AD) were used, and later, paired <i>t</i>-tests were used to generate statistics where necessary. <b>Results</b>: Post-treatment measurements were consistently lower for all four biomarkers. QQ-plots and formal tests revealed that the differences between findings were essentially normal, allowing for paired <i>t</i>-tests. The mean decreases were as follows: NLR -1.10 (95% CI -1.48 to -0.71), PLR -43.0 (-55.4 to -30.7), SII -299 (-388 to -211), and CRP -11.36 (-13.18 to -9.54), all <i>p</i> < 0.001. CRP showed the greatest drop, with significant decreases in PLR and SII and a moderate decline in NLR, indicating therapy-related attenuation of systemic inflammation. <b>Conclusions</b>: The study shows that six months of infliximab therapy results in a consistent post-treatment decrease in all four biomarkers: NLR, PLR, SII, and CRP. Because the pre-post differences were roughly normal, CRP revealed the greatest decrease, with significant decreases in PLR and SII and a moderate decrease in NLR, consistent with systemic inflammation reduction. When combined, the CBC-derived indices track with CRP and can serve as practical, low-cost markers for monitoring therapy response in RA, despite the single-arm design.