To illustrate the consequences of imperfect sensitivity and specificity on test results, consider hypothetical results (see table Distribution of Test Results of a Hypothetical Leukocyte Esterase Test in a Cohort of 1000 Women With an Assumed 30% Prevalence of UTI) of urine dipstick leukocyte esterase testing in a group of 1000 women, 300 (30%) of whom have a urinary tract infection (UTI, as determined by a gold-standard test such as urine culture).