Procalcitonin is a strong predictor of urine culture results in patients with obstructing ureteral stones: A prospective, pilot study

PURPOSE: The appropriate management of infected obstructing ureteral calculi is prompt genitourinary decompression. Urine cultures are the gold standard for confirming infection but often take 24–48 h to result. Although white blood cell (WBC) count is an important diagnostic laboratory test, it is a nonspecific inflammatory marker. Similarly, urinalysis (UA) can be misleading in the setting of a contaminated sample, bladder colonization, or in cases of a completely obstructed the upper urinary tract. Procalcitonin (PCT) has shown promise in predicting the presence and degree of bacterial infections. In this proof-of-concept study, we explore whether PCT is effective at predicting concomitant infections in the setting of obstructing ureteral stones. MATERIALS AND METHODS: This is a prospective, single-institution observational pilot study examining adult patients who presented to the emergency room with acute obstructing ureterolithiasis. In total, 22 patients were enrolled. At the time of presentation, data obtained were vital signs, WBC count, PCT, UA, urine, and blood cultures. Fisher-exact two-tailed t-tests and receiver operating characteristic statistics with area under the curve (AUC) calculations were used to determine the correlation between urine culture results and PCT, WBC count, nitrite-positive UA, heart rate, and fever. RESULTS: In total, 5/22 patients had bacteria-positive urine cultures. PCT (P = 0.020) and nitrite-positive UA (0.024) were the only statistically significant predictors of urine culture results. In comparing the AUC, PCT (0.812) was strongly correlated with eventual urine culture results. CONCLUSIONS: This proof-of-concept pilot study gives encouraging results, in that PCT was a good predictor of positive cultures (P = 0.02, AUC 0.812). Given, the small sample size, one cannot directly compare PCT to other markers of infection. However, PCT shows promise in this arena and warrants future investigation.