A-066 Pyuria Thresholds and Diagnostic Accuracy in Postmenopausal Urinary Tract Infections

Abstract

Urinary tract infection (UTI) is a frequent diagnosis in postmenopausal women =65 years, but pyuria—a key diagnostic indicator—may also occur due to atrophic vaginitis or noninfectious causes. Conventional microscopic cutoffs for pus cells lack validation in geriatric females, leading to potential overdiagnosis and inappropriate antibiotic use. The present study was a prospective case–control study conducted on 300 pyuric postmenopausal women with suspected UTI. Out of which 150 were culture positive cases with equal no of culture negative controls. Urine microscopy was assessed at pyuria thresholds of 10, 17, and 20 leukocytes/high-power field (hpf) against culture as the gold standard. Parallel evaluation was done by flowcytometry and leukocyte esterase. Diagnostic performance was analyzed using sensitivity, specificity, predictive values, and Youden index to identify the optimal pyuria cutoff for this cohort. A cutoff of 17 leukocytes/hpf on microscopy demonstrated the best balance—sensitivity 61.3% (95% CI: 53.2–69.0%), specificity 48.7% (95% CI: 40.6–56.8%), and the highest Youden index (0.10). The conventional 10/hpf threshold showed higher sensitivity (72.7%) but very low specificity (14.0%; false-positive rate 86%), while 20/hpf improved specificity (58.7%) but missed 63% of true positives. Whereas, flow cytometry cut off at =560 WBCs/mL demonstrated superior accuracy with sensitivity 85–95%; specificity 75–85% compared to microscopy. A pyuria threshold of 17 leukocytes/hpf provides an optimal balance for diagnosing UTI in postmenopausal women in Indian settings. Incorporating flow cytometry as the primary screening tool followed by microscopy in doubtful cases and culture confirmation when indicated—can enhance diagnostic accuracy and reduce unnecessary antibiotic use by approximately 35% while maintaining patient safety.