What is the predictive value of urinary symptoms for diagnosing urinary tract infection in women?

Our aim was to determine the probability of correctly diagnosing urinary tract infections (UTIs) from urinary symptoms and signs, studying their sensitivity, specificity and likelihood ratio (LR) when clinical history, signs and reactive strip test results are taken into account.

An epidemiological analysis with a diagnostic and clinical orientation was carried out in a primary health care setting. The subjects comprised 343 women > or =14 years of age who consulted their family physician for incident urinary tract symptoms. A guided medical examination was carried out using a check-list formulary, reactive strip test, urine culture and the clinical course of all patients.

The pre-test probability of having UTI among patients with incident urinary symptoms is 0.484 [95% confidence interval (CI) 0.431-0.536]. Positive LRs for UTI are: painful voiding 1.31 (95% CI 1.12-1.54), urgency 1.29 (95% CI 1.12-1.50), urinary frequency 1.16 (95% CI 1.06-1.28) and tenesmus 1.16 (95% CI 1.02-1.32). The probability of UTI is reduced by the presence of genital discomfort, dyspareunia, vaginal discharge, positive lumbar fist percussion and perineal discomfort. Nitrites on the urine reactive strip test increase the probability of UTI by >5 times, moderate pyuria increases it by >1.5 times, and the presence of both findings does so by >7 times.

In women with urinary symptoms, a thorough clinical examination, together with performance of a reactive strip test during the office visit, improves the chances of detecting UTI.