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

Area of Science:

• Clinical microbiology
• Infectious diseases
• Diagnostic accuracy

Background:

• Urine culture contributes to 27% of US hospitalizations.
• Unnecessary antibiotic prescriptions drive antimicrobial resistance.
• Urinalysis is a key diagnostic tool for urinary tract infections (UTIs).

Purpose of the Study:

• Assess urinalysis predictive value for negative urine cultures and absence of UTI.
• Re-evaluate the microbial growth threshold for positive urine culture.
• Describe antimicrobial resistance patterns in UTIs.

Main Methods:

• Retrospective study of 12,252 urinalyses and urine cultures from women (ages 18-49) from 2013-2020.
• Clinically diagnosed UTI (CUTI) defined by uropathogen growth, UTI diagnosis, and antibiotic prescription.
• Calculated sensitivity, specificity, and predictive values to assess urinalysis performance.

Main Results:

• Negative urinalysis showed high accuracy for predicting negative urine culture (90.3% specificity) and absence of CUTI (92.2% specificity).
• 10.5% of patients had CUTI; 24% received antibiotics without meeting CUTI criteria.
• 22% of CUTI cultures had <100,000 CFU/mL; *E. coli* caused 70% of CUTIs, with 4.2% ESBL producers.

Conclusions:

• Negative urinalysis is highly predictive of the absence of CUTI.
• A 10,000 CFU/mL threshold is more clinically appropriate than 100,000 CFU/mL for positive urine cultures.
• Urinalysis-based reflex cultures can enhance clinical judgment and improve antibiotic stewardship.