Optimizing reflex urine cultures: Using a population-specific approach to diagnostic stewardship

Background:Clinicians and laboratories routinely use urinalysis (UA) parameters to determine whether antimicrobial treatment and/or urine cultures are needed. Yet the performance of individual UA parameters and common thresholds for action are not well defined and may vary across different patient populations. Methods:In this retrospective cohort study, we included all encounters with UAs ordered 24 hours prior to a urine culture between 2015 and 2020 at 3 North Carolina hospitals. We evaluated the performance of relevant UA parameters as potential outcome predictors, including sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV). We also combined 18 different UA criteria and used receiver operating curves to identify the 5 best-performing models for predicting significant bacteriuria (>= 100,000 colony-forming units of bacteria/mL). Results:In 221,933 encounters during the 6-year study period, no single UA parameter had both high sensitivity and high specificity in predicting bacteriuria. Absence of leukocyte esterase and pyuria had a high NPV for significant bacteriuria. Combined UA parameters did not perform better than pyuria alone with regard to NPV. The high NPV >= 0.90 of pyuria was maintained among most patient subgroups except females aged >= 65 years and patients with indwelling catheters. Conclusion:When used as a part of a diagnostic workup, UA parameters should be leveraged for their NPV instead of sensitivity. Because many laboratories and hospitals use reflex urine culture algorithms, their workflow should include clinical decision support and or education to target symptomatic patients and focus on populations where absence of pyuria has high NPV.

Automated summary

This retrospective cohort study analyzed the relationship between urinalysis and urine culture in three hospitals in North Carolina from 2015 to 2020. The study found that no individual urinalysis parameter had both high sensitivity and high specificity in predicting bacterial infection. The absence of leukocyte esterase and pyuria had a high negative predictive value for significant bacteriuria. Combining urinalysis parameters did not perform better than pyuria alone in terms of negative predictive value. Rating: 8 out of 10