Diagnostic role of opsonic activity in Acinetobacter baumannii Ventilator-Associated Pneumonia

In this study, we investigated the diagnostic value of opsonic activity against Acinetobacter baumannii in Ventilator-Associated Pneumonia (VAP) among 50 patients, compared to 102 negative and positive controls. Out of the 50 patients, only 33 (66%) were diagnosed with VAP using the Clinical Pulmonary Infection Score (CPIS). The opsonic activity assay demonstrated three key findings: (i) 95% sensitivity and 91.7% specificity, with a Receiver Operating Characteristic (ROC) area of 0.976 for distinguishing A. baumannii culture positives from negatives; (ii) 95% sensitivity and 78.7% specificity, with a 0.915 ROC area, in differentiating VAP/blood culture positive patients from colonized/negative groups; (iii) An ROC area of 0.553 for VAP and colonization, as identified by CPIS alone, indicating an indeterminate threshold. These results highlight that CPIS, microbiological, and clinical evaluations were not correlated, suggesting that opsonic activity against A. baumannii could be a potential VAP diagnostic tool, with the need for large-scale validations.