Correlation of Pneumonia Severity Index and CURB-65 Score with Neutrophil/Lymphocyte Ratio, Platelet/Lymphocyte Ratio, and Monocyte/Lymphocyte Ratio in Predicting In-Hospital Mortality for Community-Acquired Pneumonia: Observational Study

<b>Background/Objectives</b>: Community-acquired pneumonia is a major cause of morbidity and mortality, and various scoring systems and laboratory assessments are available for predicting prognosis. The untapped potential of combining the neutrophil/lymphocyte ratio (NLR) with the monocyte/lymphocyte ratio (MLR) and platelet/lymphocyte ratio (PLR) and their correlation with the pneumonia severity index (PSI) and CURB-65 motivated our research. We thought that this would provide more robust data for predicting CAP prognosis. We aimed to assess hematologic parameters' associations with the PSI, CURB-65, and qSOFA scores for predicting the prognosis of hospitalized CAP patients. DESIGN AND SETTING: This is a multicenter, observational study conducted in three hospitals in Türkiye, Antalya. <b>Methods</b>: A total of 343 patients hospitalized with CAP in three centers in Turkey, Antalya, between 1 January 2020 and 30 September 2023 were retrospectively enrolled. The demographic data, comorbidities, vital signs, radiological images, laboratory findings, and 30-day mortality results of the patients were recorded. CURB-65, PSI, and qSOFA scores were calculated. <b>Results</b>: This study included 163 females (47%) with an average age of 74 ± 11.8. Hospital mortality occurred in 51 patients. Non-survivor CAP cases had higher ages (<i>p</i> = 0.007), CURB-65 scores (<i>p</i> < 0.001), PSIs (<i>p</i> < 0.001), and qSOFA scores (<i>p</i> < 0.001) and a longer hospital stay (<i>p</i> = 0.001) and total antibiotic duration (<i>p</i> < 0.001). Additionally, the NLR (<i>p</i> = 0.009), MLR (<i>p</i> = 0.018), and PLR (<i>p</i> = 0.025) were higher in the non-survivor group. The CURB-65, PSI, and qSOFA scores demonstrated strong predictive capabilities for in-hospital mortality. In the ROC analysis conducted to predict in-hospital mortality, the area under the curve (AUC) for CURB-65, the PSI, and qSOFA was determined to be 0.83, 0.82, and 0.82, respectively. The NLR correlated positively with CURB-65, the PSI, and qSOFA; the PLR correlated with the PSI and qSOFA; and the MLR correlated with CURB-65. <b>Conclusions</b>: CURB-65 and PSI scores remain highly effective for predicting in-hospital mortality in CAP patients, as demonstrated by their superior AUC values. While the NLR, MLR, and PLR showed weak predictive performance compared to these scores, their correlations suggest their potential as adjunctive markers.