Validity of the urinary dipstick test in the diagnosis of urinary tract infections in adults

INTRODUCTION: Utility of dipstick analysis must be investigated in patients admitted to the emergency department. The aim of this study was to evaluate if urine dipstick analysis can be used to detect significant bacteriuria. The cross-sectional study was performed in the Emergency Department of Copenhagen University Hospital - Herlev Hospital, Denmark.

METHODS: We recorded urine dipstick analysis of 500 adult patients admitted to the Emergency Department. Dipstick results were compared with urinary culture.

RESULTS: Sensitivity for leukocyte esterase (LE) was 80.9%, but specificity was 58%. The sensitivity of nitrite was 46.5%, and specificity was 90%. The positive predictive value (PPV) and negative predictive value (NPV) of LE for women were 54.5% and 75.9%; for men, 50.0% and 91.6%. PPV and NPV for nitrite in women were 85.9% and 66.8%; for men, 62.9% and 88.7%. Positive LE and positive nitrite had a PPV of 90.2% for women and 70.4% for men. Negative LE and negative nitrite had an NPV of 80.9% for women and 93.3% for men.

CONCLUSIONS: No single parameter or combination of parameters on the urine dipstick analysis can be used reliably to predict positive urine culture in women. The most accurate predictor of negative urine culture in men is the combination of negative nitrites and negative LE. To minimize unnecessary use of antibiotics, treatment can be delayed in female patients with positive urine dipstick until urine culture results are available.

FUNDING: none.

TRIAL REGISTRATION: not relevant.