Diagnostic Value of Bedside Lung Ultrasonography Plus Procalcitonin in Ventilator-associated Pneumonia

INTRODUCTION: Ventilator-associated pneumonia (VAP) is the most prevalent hospital-acquired infection in intensive care units (ICUs), with incidences varying from 5% to 40%. It is linked to significant morbidity and mortality, prolonged mechanical ventilation, and increased healthcare costs. Current diagnostic methods—clinical scoring, microbiological cultures, and radiological assessments—have limitations in specificity and sensitivity.(1–3) OBJECTIVES: 1. To assess the diagnostic performance of the combination of lung ultrasound and procalcitonin (PCT) in mechanically ventilated subjects who exhibit symptoms indicative of pneumonia. 2. Compare the diagnostic capability of lung ultrasound combined with PCT to diagnose VAP with that of lung ultrasound alone, PCT, Clinical Pulmonary Infection Score alone, and chest x-ray. MATERIALS AND METHODS: This prospective study was conducted at Indraprastha Apollo, New Delhi from July 2021 to November 2022, and included 90 patients on mechanical ventilation for ≥48 hours with clinical suspicion of VAP. Clinical suspicion was based on at least two of the following: body temperature ≥38.0°C or <36.0°C, WBC count ≥10,000 or <4,000 cells/mm(3), purulent tracheal secretions, and PaO2/FIO2 <300 mmHg. Lower respiratory tract cultures and serum PCT were obtained. A cut-off value of PCT ng/ml was taken as an indication of bacterial pneumonia for the study. For each individual, VAP was diagnosed based on clinical features plus a positive quantitative bacterial culture of the lower respiratory tract sample. A lung ultrasound was done by an intensivist trained in lung ultrasonography after inclusion in the study. Small subpleural consolidations, Lobar Hemilobar consolidation, and Dynamic air bronchogram were considered positive results for VAP on ultrasound. METHOD OF MEASUREMENT OF OUTCOME: Diagnostic performance was assessed by sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for LUS, PCT, CPIS, chest X-ray, and the LUS + PCT combination. Results: LUS combined with PCT showed a sensitivity of 71.67%, specificity of 86.67%, PPV of 91.49%, and NPV of 60.47% for diagnosing VAP. The diagnostic accuracy of this combination was 76.67%. In contrast, LUS alone, CPIS, serum PCT, and chest X-ray demonstrated lower diagnostic accuracy. Discussions/Conclusions: Our study suggests that combining lung ultrasound with procalcitonin offers a reliable diagnostic tool for VAP, with higher specificity and PPV, although the sensitivity was lower compared to other methods. This combination is particularly useful for excluding VAP in patients with a low likelihood of infection. However, further research is needed to explore the optimal use of these tools and identify additional biomarkers or diagnostic strategies to enhance the accuracy of VAP diagnosis.