Diagnostic performance evaluation of complete urinalysis in the diagnosis of urinary tract infection

Aim: The aim was to evaluate the adequacy of the diagnostic performance of urinalysis parameters in the diagnosis of urinary tract infection.

Materials and Methods: In this retrospective study, the results of 13,315 individuals who had urine culture and complete urinalysis were analyzed. Midstream urine culture results were taken as a reference in the diagnosis of urinary tract infections. The diagnostic performance of urinalysis’ chemical parameters [appearance, leukocyte esterase(LE), nitrite] and microscopic parameters (bacteria and squamous epithelium) individually and in combination were evaluated. Two different cut-off values (trace and 1+) were used while performing the analysis. Sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratios were calculated. The area under the curve (AUC) was evaluated with receiver operating curve (ROC) analysis.

Results: Of the samples, 10.1% were evaluated as culture positive. The highest sensitivity rate was observed in the combination of the presence of any of the LE (trace), nitrite (trace), and bacteria parameters (86%). When evaluated as a single parameter, the highest sensitivity was observed in the LE(trace) parameter (81.6%). The negative predictive value was >90% in both single-parameter and combination evaluations. The AUC of the LE and nitrite tests was calculated as 0.758 and 0.718, respectively.

Conclusion: The parameters evaluated in this study, singly or in combination, showed sufficient performance in predicting negative urine cultures. Although complete urinalysis analyses cannot replace culture examinations, we believe that they can reduce unnecessary culture examinations.