Diagnostic Accuracy of Lung Ultrasound versus Chest Radiograph for Early Diagnosis of Ventilator-associated Pneumonia: An Observational Study

Introduction: Ventilator-associated Pneumonia (VAP) is one of the leading causes of morbidity and mortality in intensive Intensive Care Unit (ICU) and is diagnosed by clinical symptoms, Chest X-ray (CXR), Computerised Tomography (CT) and microbiology test in routine practice.

Aim: To compare the diagnostic accuracy of Lung Ultrasound (LUS) with gold standard CXR, with or without modified Clinical Pulmonary Infection Score (CPIS) score, for the diagnosis of VAP in ICU.

Materials and Methods: This prospective observational study was carried out on 40 mechanically ventilated patients in Indira Gandhi Medical College and Hospital, Shimla, Himachal Pradesh, India over the duration of one year from November 2018 - October 2019. The study was continued till VAP was diagnosed by all three modalities (CXR, LUS and microbiology) or to the maximum of 10 days postintubation whichever was less. Data was analysed with appropriate statistical tools “MedCalc”.

Results: The mean age of patients was 45.78±15.99 years and there were 28 male and 12 females. The diagnosis of VAP was earliest with LUS (3.1±0.81 days) and (4.22±1.23 days) with CXR when studied alone (p<0.0001). However, when LUS was incorporated in CPIS score instead of CXR the diagnostic accuracy were statistically similar (p>0.05). During the early days (3 &4 day) the diagnostic accuracy (AUC), sensitivity and specificity of LUS was better and was (0.70-0.74, 57-90%) than (0.5; 16.7-83%) with CXR. Fifth day onwards AUC was better with CXR (0.79-0.81) as compared to (0.54-0.70) with LUS. Total leucocyte count (TLC), fever, P/F ratio and sputum quantity were observed individually between the VAP and non VAP group patients and were found to be similar (p>0.05).

Conclusion: According to the present observational study, LUS can accurately diagnose VAP when other objective tools like CPIS, CXR and microbiology are inconclusive.