Based on our team's previous discovery of a unique type of squamous epithelial cell in the bronchoalveolar lavage fluid (BALF) of patients with aspiration pneumonia (AP) using microbiological rapid on-site evaluation (M-ROSE) technology-characterized by its distinct morphology and absence of bacterial adhesion on the surface-which we termed "showering cells," we designed a diagnostic test case-control study. Adult patients with pulmonary infection scheduled to undergo bronchoscopy were screened and allocated into an AP group (experimental group) and a non-AP group (control group). BALF sampling and M-ROSE slide preparation were performed following a standardized protocol. Microscopic examination was conducted to detect and manually count "showering cells." Simultaneously, a committee of respiratory and critical care medicine experts determined the gold-standard diagnosis (AP or non-AP) based on composite clinical criteria.
A 2×2 contingency table was constructed to calculate sensitivity, specificity, positive/negative likelihood ratios, positive/negative predictive values along with their 95% confidence intervals, and the kappa agreement rate. A receiver operating characteristic (ROC) curve was plotted to evaluate the diagnostic performance of "showering cells" for aspiration pneumonia, from which the area under the curve (AUC) was calculated and the optimal cutoff value determined. This study aims to assess the diagnostic utility of "showering cells" and provide a novel cytomorphological tool for the diagnosis of aspiration pneumonia.