Urinalysis Exhibits Excellent Predictive Capacity for the Absence of Urinary Tract Infection

Abstract

Objective: To assess predictive value of urinalysis for negative urine culture and absence of urinary tract infection, re-evaluate the microbial growth threshold for positive urine culture result, and describe antimicrobial resistance features. Urine culture is associated with 27% of U.S. hospitalizations, and unnecessary antibiotic prescription is a main antibiotic resistance contributor.

Methods: Urinalyses with urine culture from women ages 18-49 from 2013 to 2020 were studied. Clinically diagnosed urinary tract infection (CUTI) was defined as (1) uropathogen growth, (2) documented diagnosis of urinary tract infection, and (3) antibiotic prescription. Sensitivity, specificity, and diagnostic predictive values were used to assess urinalysis performance in predicting isolation of a uropathogen by culture and in detection of CUTI.

Results: Total 12,252 urinalyses were included. Forty-one percent of urinalyses were associated with positive urine culture and 1287 (10.5%) with CUTI. Negative urinalysis exhibited high predictive accuracy for negative urine culture (specificity 90.3%, PPV 87.3%) and absence of CUTI (specificity 92.2%, PPV 97.4%). Twenty-four percent of patients not meeting the CUTI definition were still prescribed antibiotics. Twenty-two percent of cultures associated with CUTI exhibited growth less than 100,000 CFU/mL. Escherichia coli was implemented as causing 70% of CUTIs, and 4.2% of these produced an extended spectrum beta-lactamase.

Conclusion: Negative urinalysis exhibits high predictive accuracy for absence of CUTI. A reporting threshold of 10,000 CFU/mL is more clinically appropriate than a 100,000 CFU/mL cutpoint. Reflex culture based on urinalysis results could complement clinical judgement and improve laboratory and antibiotic stewardship in premenopausal women.