Comparative Prognostic Value of Serum Albumin, Prognostic Nutritional Index, and CRP-to-Albumin Ratio for In-Hospital Mortality in Hospitalized Pneumonia: A Retrospective Cohort Study

Abstract

Aim: Pneumonia is a major cause of in-hospital mortality, particularly in older patients with multiple comorbidities. The comparative value of nutritional–inflammatory indices in this setting remains insufficiently clarified. We compared serum albumin, the Prognostic Nutritional Index (PNI), and the C-reactive protein/albumin ratio (CAR) as predictors of in-hospital mortality in adults hospitalized for pneumonia. Materials and Methods: We retrospectively reviewed 294 adults (aged 18–90 years) hospitalized with pneumonia between January 2023 and January 2026. Patients with active malignancy, advanced hepatic failure, protein-losing conditions, or ongoing immunosuppression were excluded. PNI was calculated as (10 × albumin [g/dL]) + (0.005 × lymphocyte count [/mm³]) and CAR as CRP (mg/L) / albumin (g/L). The primary endpoint was in-hospital all-cause mortality. Independent predictors were identified by logistic regression, with multicollinearity assessed by variance inflation factors (VIF). Discrimination was evaluated by ROC analysis with the Youden index. Results: In-hospital mortality was 16.3% (48/294). Serum albumin showed the highest AUC (0.680; 95% CI 0.605–0.751; cutoff ≤32.5 g/L; sensitivity 67%, specificity 51%); PNI (AUC=0.611) and CAR (AUC=0.606) showed lower discrimination. Pairwise AUC comparisons (DeLong) were not performed, so the ordering is descriptive. In multivariable analysis, lower albumin (OR 0.840 per g/L, 95% CI 0.757–0.932; p=0.001), respiratory failure, and ICU admission were independent correlates of mortality; CAR was non-significant. No meaningful collinearity was observed between albumin and CAR (VIF=1.002 for both). Mortality was higher with PNI <45 than ≥45 (18.5% vs 5.9%; p=0.027), but PNI category was unrelated to etiologic distribution or resistant pathogen isolation. Conclusion: Admission serum albumin was independently associated with in-hospital mortality and showed numerically higher discrimination than PNI and CAR. Composite indices added no measurable prognostic value beyond albumin. These findings support admission albumin as a practical early risk marker, pending prospective confirmation against validated severity scores.

Keywords

• Pneumonia
• Serum Albumin
• Prognostic Nutritional Index
• CRP-to-Albumin Ratio
• Mortality
• Prognosis

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