The prognostic value of the prognostic nutritional index in patients with sarcoidosis.

BACKGROUND: Sarcoidosis is a heterogeneous multisystem granulomatous disease with an unpredictable clinical course. Reliable biomarkers for predicting relapse remain limited. The Prognostic Nutritional Index (PNI), reflecting systemic inflammation and immunonutritional status, has emerged as a prognostic marker in various inflammatory and pulmonary diseases. However, its role in sarcoidosis has not been sufficiently clarified. This study aimed to investigate the association between baseline PNI levels and relapse in patients with sarcoidosis. METHODS: This retrospective single-center study included 302 adult patients diagnosed with sarcoidosis between January 2015 and January 2025. Baseline laboratory parameters, including serum albumin, lymphocyte count, C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), were recorded. PNI was calculated as: 10 × serum albumin (g/dL) + 0.005 × total lymphocyte count (/mm³). The primary outcome was disease relapse during follow-up. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive performance of baseline PNI. RESULTS: Relapse occurred in 52 patients (17.2%) during follow-up. Patients who developed relapse had significantly lower baseline albumin levels, lymphocyte counts, and PNI values, and significantly higher CRP, NLR, and PLR levels (all p<0.01). Baseline PNI demonstrated excellent discriminative ability for predicting relapse, with an area under the curve (AUC) of 0.922 (95% CI: 0.887-0.957, p<0.001). A cutoff value of ≤39.25 yielded a sensitivity of 94.2% and a specificity of 82.8%. CONCLUSION: Lower baseline PNI values are strongly associated with relapse in patients with sarcoidosis and show excellent predictive performance. As a simple, inexpensive, and widely available biomarker reflecting both inflammatory burden and immune competence, PNI may serve as a practical tool for risk stratification and individualized follow-up in clinical practice. Prospective multicenter studies are warranted to validate these findings.