Predictors of ICU Admission and In-Hospital Mortality in Hospitalized Patients With Lupus Nephritis: The Prognostic Value of Neutrophil-to-Lymphocyte Ratio and C Reactive Protein to Serum Albumin Ratio

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease characterized by immune dysregulation, autoantibody production, immune complex deposition, and complement activation, leading to inflammation and irreversible organ damage. Despite advances in immunosuppressive therapy, SLE remains associated with significant morbidity, frequent hospitalizations, and premature mortality. Lupus nephritis (LN), affecting approximately 40-60% of patients with SLE, is one of its most severe manifestations and a major cause of chronic kidney disease, endstage kidney disease, cardiovascular complications, recurrent hospitalizations, and death. Hospitalized patients with LN often develop severe disease flares, acute kidney injury, nephrotic syndrome, infections, pulmonary hemorrhage, neuropsychiatric lupus, thrombotic microangiopathy, or cardiovascular complications requiring intensive care, where mortality remains high Early identification of patients at risk of clinical deterioration is essential to improve monitoring and optimize treatment. Several demographic, clinical, and laboratory factors have been linked to poor outcomes, including older age, active disease, infection, impaired kidney function, thrombocytopenia, hypocomplementemia, and hypoalbuminemia. However, most available studies are retrospective or limited to selected SLE populations.

Recently, inexpensive inflammatory biomarkers derived from routine laboratory tests have gained attention. The neutrophil-to-lymphocyte ratio (NLR) reflects systemic inflammatory activity and has been associated with disease activity, acute kidney injury, ICU admission, and mortality. The C-reactive protein-to-albumin ratio (CAR), combining inflammatory and nutritional status, has also demonstrated prognostic value in inflammatory and critically ill patients.

This prospective observational cohort study aims to identify the clinical and laboratory predictors of ICU admission and in-hospital mortality among hospitalized patients with lupus nephritis, with particular emphasis on evaluating the prognostic performance of NLR and CAR as simple, readily available biomarkers for early risk stratification.