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.

Keywords:

• urinary tract infection
• Candida
• antibiotics
• microscopy
• urine culture
• NABY score

Acknowledgments

We thank Rommanee Khositnithikul, PhD from Clinical Pathology Program, Faculty of Medicine Ramathibodi Hospital, Mahidol University for providing the information on urinalysis.

Data Sharing Statement

Data can be made available through contact with the corresponding author.

Disclosure

The authors report no conflicts of interest in this work.