Predictive Value of Urinalysis and Recent Antibiotic Exposure to Distinguish Between Bacteriuria, Candiduria, and No-Growth Urine

Abstract

Purpose: Urinary tract infections are diagnosed by clinical symptoms and detection of causative uropathogen. Antibiotics are usually not indicated in candiduria and no-growth urine. We aimed to develop a predictive score to distinguish bacteriuria, candiduria, and no-growth urine, and to describe the distribution of microorganisms in urine. Patients and Methods: A single-center, retrospective cohort study was conducted between January 2017 and November 2017. Patients with concomitant urinalysis and urine culture were randomly sorted for a clinical prediction model. Multivariable regression analysis was performed to determine factors associated with bacteriuria, candiduria, and no-growth urine. A scoring system was constructed by rounding the regression coefficient for each predictor to integers. Accuracy of the score was measured by the concordance index (c-index). Results: There were 8091 positive urine cultures: Bacteria 85.6%, Candida 13.7%. Randomly selected cases were sorted into derivation and validation cohorts (448 cases and 272 cases, respectively). Numerous yeast on urinalysis predicted candiduria with complete accuracy; therefore, it was excluded from a score construction. We developed a NABY score based on: Positive nitrite, 1 point; Antibiotic exposure within 30 days, -2 points; numerous Bacteria in urine, 2 points; few Yeast in urine, -2 points; moderate Yeast in urine, -5 points. The c-index was 0.85 (derivation) and 0.82 (validation). A score ≥0 predicted 76% and 54% of bacteriuria in the derivation and validation cohorts, respectively. A score ≤−3 predicted 96% of candiduria in both cohorts. Conclusion: Numerous yeast on urinalysis and the NABY score may help identify patients with a low risk of bacteriuria in whom empiric antibiotics for UTIs can be avoided.