The impact of decreased prognostic nutritional index on the prognosis of patients with pneumonia treated with glucocorticoids: a multicenter retrospective cohort study.

Background: Long-term or high-dose glucocorticoid administration can markedly impair immune responses, mask clinical indicators of pulmonary infections, and increase the susceptibility to refractory pneumonia, leading to heightened mortality risk. The Prognostic nutritional index (PNI), derived from peripheral lymphocyte count and serum albumin (ALB) levels, serves as a reliable indicator for evaluating nutritional and immune statuses across various clinical populations, including oncology patients, individuals with cardiovascular disorders, and perioperative patients. However, the predictive value of PNI in pneumonia patients receiving glucocorticoids, especially within the Chinese population, has not been sufficiently investigated. This observational analysis aimed to explore the correlation between PNI levels and all-cause mortality (ACM) in patients undergoing prolonged glucocorticoid therapy for pneumonia. Methods: A retrospective cohort study was conducted utilizing data extracted from the Dryad database. Kaplan-Meier curves, multivariable Cox regression, restricted cubic splines (RCS), and subgroup analyses were used to assess the association between PNI and ACM in patients with pneumonia who received glucocorticoids. Results: The study incorporated a total of 639 pneumonia patients who received glucocorticoid therapy. The ACM rates were 22.5% at 30 days and rose to 26.0% at 90 days. Multivariable Cox regression showed that, after full adjustment for potential confounders, every 2-unit decrease in PNI was associated with a 10% higher 30-day mortality hazard (HR = 1.10, 95% CI = 1.05-1.15, p < 0.001) and a 9% higher 90-day mortality hazard (HR = 1.09, 95% CI = 1.04-1.14, p < 0.001). Compared with patients with PNI ≥ 43, patients with PNI < 43 had a 118% increased risk of 30-day mortality (HR = 2.18, 95% CI = 1.28-3.81, p = 0.005) and a 96% increased risk of 90-day mortality (HR = 1.96, 95% CI = 1.20-3.19, p = 0.008). Further validation using RCS analysis revealed a robust inverse relationship between PNI scores and ACM, and subgroup analyses revealed no significant interactions. Conclusion: Among pneumonia patients receiving glucocorticoid therapy, a decreased PNI was associated with an increased risk of 30-day and 90-day mortality, particularly in those with a PNI < 43.