Objective

Postoperative pneumonia (POP) frequently complicates cardiac surgery that involves cardiopulmonary bypass (CPB). This study aimed to assess the diagnostic utility of procalcitonin (PCT) for identifying pneumonia after CPB-assisted cardiac surgery.

Methods

Patients diagnosed with POP were enrolled in the retrospective matched case-control study and were admitted to a Grade III general hospital in Nanjing in 2023. POP diagnosis was determined based on a combination of clinical and microbiological criteria.PCT and white blood cell count (WBC) data were systematically collected from day 1 (T1) to day 5 (T5). Receiver operating characteristic (ROC) curve analysis and subject operating characteristics were utilized to evaluate the diagnostic performance of biomarkers. At the same time, a binary logistic regression model was developed to identify factors that influence the diagnosis of POP.

Results

The study included 220 age- and sex-matched patients, comprising 56 individuals with POP and 164 uninfected patients constituting the non-POP group. ROC curve analysis revealed that serum PCT concentration exhibited an AUC > 0.7 from day 2 to day 5, whereas other indices demonstrated AUCs < 0.7 at these time points. Univariate and multivariate analyses highlighted serum PCT concentration on day 2, WBC count on day 5, the PCTT4-T1 variation rate, and days of mechanical ventilation as significant predictive factors for POP diagnosis, each demonstrating statistical significance (P < 0.05). The calculated AUC was 0.837 (95%CI: 0.773–0.902). The absolute PCT value exhibited superior diagnostic performance relative to its variance rate and WBC count, yielding optimal diagnostic accuracy with a cutoff value of 3.45 ng/ml.

Conclusion

Serum PCT absolute value demonstrates higher sensitivity and specificity than other indices, offering superior diagnostic potential for predicting POP.