National Research Institute of Tuberculosis and Lung Disease (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran TANAFFOS (Respiration) 1735-0344 16 1 2017 01 01 Diagnostic Yield of a Direct Quantitative Smear of Lower Respiratory Tract Secretions in Patients with Suspected Pneumonia Compared to a Semi-quantitative Culture 9 12 240195 EN Shervin Shokouhi Infectious Diseases and Tropical Medicine Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Ilad Alavi Darazam Infectious Diseases and Tropical Medicine Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Maryam Sadeghi Infectious Diseases and Tropical Medicine Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Latif Gachkar Infectious Diseases and Tropical Medicine Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Samaneh Dolatshahi Infectious Diseases and Tropical Medicine Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Journal Article 2020 12 25 Background: Microorganism isolation from respiratory tract specimens is the standard of care in patients with suspected nosocomial and ventilator associated pneumonia. However, these methods are time-consuming and are influenced by several factors. A direct quantitative smear (DQS) with proper staining may be an easy, cost-effective, rapid method. We evaluated the diagnostic yield of direct smears compared to semi-quantitative culture methods. Materials and Methods: Hospitalized, intubated patients with clinically suspected pneumonia and patients who underwent diagnostic bronchoscopic alveolar lavage (BAL) and trans-endotracheal aspiration (TEA) were enrolled in a prospective study. The obtained specimens were Gram stained and microorganisms were computed per 10 high-power fields (HPFs) of light microscopy. All samples were cultured by a standard semi-quantitative method. Colony-forming units (CFU) >104/mL and >105 CFU/mL were reported as culture-positive for BAL and TEA, respectively. Results: A total of 331 respiratory specimens were analyzed. Based on culture results, the best cut-off point was 35 microorganisms in 10 HPFs of microscopy and provided 90.4% sensitivity and 90.8% specificity. The best cut-off point for 25 microorganisms in 10 fields of light microscopy provided 95.2% sensitivity and 85.7% specificity. Conclusion: A DQS obtained by BAL and TEA may be a reliable and rapid method to diagnose pneumonia and anticipate semi-quantitative culture results. The sensitivity and specificity of a direct smear have adequate diagnostic yield to recommend it as an adjunct to microorganism-isolation methods. https://www.tanaffosjournal.ir/article_240195_988f1d97856a933be6b65c5502f27b30.pdf