Evaluation of evidence-based urinalysis reflex to culture criteria: Impact on reducing antimicrobial usage.

OBJECTIVES

To implement evidence-based urinalysis (UA) reflex criteria and to evaluate the impact of the intervention on reducing unnecessary antibiotic usage.

METHODS

A prospective intervention study was conducted on 4130 urine samples that were subjected to UA during March to May 2020. Results were analyzed in order to evaluate the effectiveness of newly implemented evidence-based criteria in predicting positive urine cultures. The intervention involved implementing evidence-based UA reflex criteria to ensure a high predictive value of the UA reflex parameters. Multivariable logistic regression was utilized to evaluate the effectiveness of these UA parameters in predicting positive urine cultures and to assess the impact of the new UA criteria on antibiotic usage.

RESULTS

A total of 4130 patient samples were included in the study; 60.1% (n = 2484) were from female patients and 39.9% (n = 1646) were from male patients. The total number of negative urine reflex samples was 3116, which accounted for 75.4% of the total UA reflex samples. In contrast, 24.6% of the urine reflex samples (n = 1014) returned positive UA results and were reflexed to urine culture. Among the urine samples that were cultured, 9% (n = 91) were negative urine cultures, while 91.0% (n = 923) were positive urine cultures. Chi-square analysis indicated highly statistically significant associations between the combination parameters of (≥5 white blood cells (WBCs) and positive nitrite) and positive urine cultures (Chi-square = 516.428, p < 0.001) and (≥5 WBCs and moderate or large esterase) and positive urine cultures (Chi-square = 503.387, p < 0.001). Additionally, Chi-square analysis indicated a highly statistically significant association between the combination parameters of (≥5 WBCs and ≥1 bacteria) and positive urine cultures (Chi-square = 434.806, p < 0.001). The statistical analysis showed that the implementation of evidence-based UA reflex criteria significantly decreased the number of urine cultures performed and potentially decreased the number of patients inappropriately treated with antibiotics from 45.1% to 9%.

CONCLUSIONS

In conclusion, ≥5 WBCs and positive nitrite yielded the highest positive predictive value of 98.00% and showed a highly significant association with positive urine cultures. It was observed that the new UA reflex criteria are highly effective in predicting positive urine cultures, thus potentially resulting in the reduction of unnecessary antibiotic usage.