Clin Infect Dis. 2023 Feb 20:ciad099. doi: 10.1093/cid/ciad099. Online ahead of print.
BACKGROUND: Pre-existing lower urinary tract symptoms (LUTS), cognitive impairment and the high prevalence of asymptomatic bacteriuria (ASB) complicate the diagnosis of urinary tract infection (UTI) in older women. The presence of pyuria remains the cornerstone of UTI diagnosis. However, over 90% of ASB patients have pyuria, prompting unnecessary treatment. We quantified pyuria by automated microscopy and flowcytometry to determine the diagnostic accuracy for UTI and to derive pyuria thresholds for UTI in older women.
METHODS: Women ≥ 65 years with ≥ 2 new-onset LUTS and one uropathogen ≥ 104 colony-forming units/mL (CFU/mL) were included in the UTI-group. Controls were asymptomatic and classified as ASB (one uropathogen ≥ 105 CFU/mL), negative culture or mixed flora. Patients with an indwelling catheter or antimicrobial pretreatment were excluded. Leukocyte medians were compared and sensitivity-specificity pairs were derived from a receiver operating characteristic-curve.
RESULTS: We included 164 participants. UTI patients had higher median urinary leukocytes compared to control patients (microscopy: 900 versus 26 leukocytes/µl; flowcytometry 1575 versus 23 leukocytes/µl, p < 0.001). Area under the curve was 0.93 for both methods. At a cut-off of 264 leukocytes/µl, sensitivity and specificity of microscopy were 88% (positive and negative likelihood ratio 7.2 and 0.1, respectively). The commonly used cut-off of 10 leukocytes/µl had a poor specificity (36%) and a sensitivity of 100%.
CONCLUSION: The degree of pyuria can help to distinguish UTI in older women from ASB and asymptomatic controls with pyuria. Current pyuria cut-offs are too low and promote inappropriate UTI diagnosis in older women.