Old Age, B Cell Function and Count Are the Critical Factors for Predicting Infection Risk in Patients With Autoimmune Rheumatic Diseases Undergoing Immunosuppression: A Cohort Study

Objective: The study aims to assess baseline immune parameters that predict infection risk in autoimmune rheumatic disease (ARD) patients, with the goal of identifying high-risk individuals requiring immunosuppressive therapy escalation, based on infection rates during a one-year follow-up. Methods: The independent cohort study was conducted at a tertiary rheumatology center in India from December 2019 to March 2022. It included adult participants with ARDs undergoing immunosuppression. Ethics approval and informed consent were obtained. Patients underwent detailed history, clinical examination, and baseline investigations, which included complete hemogram, inflammatory parameters, immunoglobulin levels, cellular levels of the immune system, complement levels, and viral markers. Descriptive statistics, ANOVA, chi-squared tests, t-tests, and Fisher's exact tests were used. OLS regression analyses identified significant predictors of infection risk. They were followed up for a period of 1 year for any infection episodes. Results: Of the 106 participants recruited, 4 were excluded due to disease-related complications during the 3-month period of follow-up. The mean age of the participants was 38.21 +/- 12.73 years, with an average follow-up duration of 13.1 +/- 8.35 months. Among the remaining 102 participants, younger age was associated with a lower infection risk (OR 1.047). Protective factors against infection included lower levels of immunoglobulin E (IgE) (OR 0.379), methotrexate (MTX) use (OR 0.247), and biologics (OR 0.543). Conversely, lower Immunoglobulin G (IgG), elevated neutrophil counts (OR 3.588), higher neutrophil-to-lymphocyte ratios (NLR) (OR 2.577), low platelet counts (OR 0.546), and steroid use, which increased the risk fivefold (OR 5.686), were identified as risk factors. Ordinary Least Squares (OLS) regression analysis highlighted age, IgG levels, CD19 lymphocyte counts, WBC counts, and ESR as significant predictors of infection risk between the groups. Conclusion: Older age, low IgG, low B cell count (CD19) predict susceptibility to infections; high neutrophil counts, low platelets, and elevated NLR are key predictors of developing infection in ARDs patients. Careful monitoring and tailored treatment strategies are essential to reduce infection risks. Further research is needed in this direction to develop predictive algorithms.