Clinical and Immunological Determinants of Glomerular Filtration Rate in Iraqi Patients with Systemic Lupus Erythematosus

Abstract

Objective: To identify clinical, immunological, and cardiometabolic factors associated with estimated glomerular filtration rate (eGFR) in Iraqi patients with systemic lupus erythematosus (SLE) and to describe the distribution of chronic kidney disease (CKD) stages in this group. Methods: This cross-sectional study included 44 patients with SLE attending Baghdad Teaching Hospital, Baghdad, Iraq, between September 2023 and March 2024. Age, sex, body mass index (BMI), blood pressure, antinuclear antibody (ANA) level, erythrocyte sedimentation rate (ESR),white blood cell (WBC) count, and serum creatinine (SCR) were recorded, and eGFR was calculated with the CKD-EPI 2021 equation. Group comparisons, correlation analysis, and multiple linear regression were performed. Results: Most patients were female (88.6%), and the mean age was 42.05 ± 12.87 years. Five patients (11.4%) had CKD (eGFR <60 mL/min/1.73 m²) and eight (18.2%) had hypertension. Patients with CKD had higher SCR than those without CKD (p < 0.001). eGFR correlated negatively with age (Spearman ρ = −0.547, p < 0.001) and SCR (ρ = −0.865, p < 0.001). In multiple regression, age was independently associated with lower eGFR (β = −1.475, p < 0.001). ANA was also associated with eGFR (β = 1.579, p = 0.002), but this association depended on a single patient and was no longer significant when that patient was excluded. BMI was not associated with eGFR. The model explained 42.6% of the variance in eGFR (adjusted R² = 0.331). ESR was higher in female than in male patients (p = 0.036). Conclusions: Older age was the factor most consistently associated with lower eGFR, whereas BMI, blood pressure, and inflammatory markers were not. Routine monitoring of SCR, eGFR, and blood pressure, with closer follow-up of older patients, may support early detection of renal impairment. Larger prospective studies are needed to confirm these findings.