Manual method versus flow cytometry for diagnosing spontaneous bacterial peritonitis

Abstract

ABSTRACT Background Diagnosing spontaneous bacterial peritonitis (SBP) requires a high clinical index of suspicion because the clinical presentation varies widely. Early detection and treatment of SBP are crucial for improving survival rates. Ascitic fluid neutrophil count ≥ 250 cells/mm3 is the only required criterion to diagnose SBP, regardless of culture results. The most frequently used manual ascitic neutrophil counting is difficult and time-consuming, and it often leads to frequent delays in obtaining results and a possible under- or overestimation of the neutrophilic count. The flow cytometric counting provides results in 30 minutes and is more accurate, with sensitivity and specificity approaching 100%. Objective This study aimed to assess the diagnostic efficacy of manual counting of neutrophils in comparison to flow cytometry for detecting SBP. Patients and methods In a cross-sectional study, we included 140 cirrhosis-related ascites patients who were clinically suspected to have SBP and admitted to the Alexandria Main University Hospital in the Department of Internal Medicine. Participants with ≥ 250 neutrophil cells/mm3 in ascitic fluid by flow cytometry were defined as SBP patients. In contrast, those with fewer than 250 neutrophil cells/mm3 in ascitic fluid using the flow cytometric method were defined as patients without SBP. Results At a cutoff value of 250 cells/mm3, the ROC curve showed that the manual ascitic fluid method had lower sensitivity, specificity, positive and negative predictive values (67.19%, 86.84%, 81.13%, and 75.86%, respectively, with AUC = 0.945, 95% CI, 0.91–0.97, p < 0.001) in diagnosing SBP than the flow cytometric method. Conclusions Using the flow cytometric method significantly improved diagnostic precision. Its use may be recommended to replace the traditional manual method, which may have unaccepted false-negative results.