Prognostic Value of the C-reactive Protein-to-Lymphocyte Ratio (CLR) for Lupus Nephritis: Comparison With Neutrophil-to-Lymphocyte Ratio (NLR) and Fibrinogen-to-Albumin Ratio (FAR).

Background This study aimed to evaluate the prognostic value of C-reactive protein-to-lymphocyte ratio (CLR) in lupus nephritis (LN), and compare its utility with neutrophil-to-lymphocyte ratio (NLR) and fibrinogen-to-albumin ratio (FAR). Methods We retrospectively enrolled 359 newly diagnosed or immunosuppressant-free LN patients, including 215 with renal biopsy data. A composite endpoint was used to define poor renal prognosis. Baseline CLR, NLR, and FAR at first hospitalization were compared between patients with and without poor prognosis, and their correlations with clinical characteristics were analyzed. Prognostic value was assessed using receiver operating characteristic (ROC) analysis, Kaplan-Meier survival analysis, and least absolute shrinkage and selection operator (LASSO) Cox regression. Results Over a median follow-up of 36 months, 137 patients reached the composite endpoint. Baseline CLR, NLR, and FAR were significantly elevated in the endpoint group. CLR exhibited the strongest correlation with disease activity (SLEDAI) compared to NLR and FAR, and correlated significantly with active pathological lesions (activity index, endocapillary hypercellularity). The area under the ROC curve (AUC) for CLR in predicting poor prognosis was 85.94%, significantly higher than that of NLR or FAR. Patients with CLR >2.23 (optimal cut-off) had significantly poorer renal outcomes. LASSO Cox regression identified CLR as an independent predictor of poor renal prognosis, regardless of whether pathological parameters were included.  Conclusion CLR demonstrates superior prognostic value for renal outcomes in LN compared to NLR and FAR. Its strong association with disease activity and pathological findings suggests CLR may serve as a valuable, readily available early warning biomarker in clinical practice.