A systematic review including 70 studies with a total of 84,396 subjects was abstracted in DARE. Studies that used semi-quantitative or quantitative urine culture as the reference standard of diagnosis were eligible for inclusion. The sensitivity of nitrite testing was generally low (45 to 60%) with higher specificity (85 to 98%). Positive predictive values for nitrites were greater than or equal to 80% in elderly people and in family medicine. Compared with nitrites, sensitivity was slightly higher with leukocyte-esterase (48% to 86%) and specificity was slightly lower (17 to 93%). Negative predictive values were high for both tests in all patient groups and settings, except for family medicine. Combined leukocyte esterase and nitrite tests (one or both positive equals a positive result) produced generally increased sensitivities and had varying effects on specificities. Using this combination, overall accuracy was high in urology patients (Diagnostic odds ratio (DOR) 52, 95% CI: 48 to 56), children (DOR 46, 95% CI: 23 to 95) and where clinical information was present (DOR 28, 95% CI: 18 to 44). Sensitivity was highest in family medicine (90%, 95% CI: 89 to 92).
A systematic review examined the use of urine leukocyte esterase and nitrite tests in adults to exclude or rule out urinary tract infection (UTI). 23 trials, which used a cut-off of 108 colony-forming units per liter, were combined in a meta-analysis. The leukocyte esterase or nitrite test combination, with one or the other test positive, was used in 14 studies, showed the highest sensitivity and the lowest negative likelihood ratio. While there was significant heterogeneity between the studies, 7 of 14 demonstrated significant decreases in pretest to posttest probability with a pooled posttest probability of 5% for the negative result. In certain circumstances, there is evidence for the use of urinalysis as a rule-out test for UTI.
A cross-sectional study included 616 consecutively enrolled participants suspected of having a urinary tract infection. The optimal test characteristics were obtained when index test positivity was defined as any leucocyte esterase reaction and/or a nitrite reaction and reference test positivity was defined as a urine culture with a growth of at least 103 colony-forming units/mL (sensitivity: 88.2% (95% CI 81.6 to 93.1), negative predictive value: 93.0% (95% CI 88.9 to 95.9)). The post-test probability of a positive urine culture after a negative urinary dipstick test was 7% in the obstetric/gynaecology clinic and 8% in the internal medicine clinic.
Comment: The quality of evidence is downgraded by heterogeneity (wide range of reported results).