Urinary tract infections (UTIs) are one of the most common reasons women seek treatment in the emergency department (ED). The biomarker procalcitonin (PCT) has gained popularity over the last decade to improve the diagnosis of bacterial infections and reduce unnecessary exposure to antibiotics. PCT has been extensively studied in patients with pneumonia and sepsis and may have additional role in UTI.

A retrospective study of patients who presented to the ED in which a urinalysis test and a PCT level was obtained within the first 24h of presentation. Signs and symptoms of UTI and urine cultures were reviewed to determine a positive diagnosis of UTI. The area under the receiver operating curve was used to calculate the test characteristics of PCT. Different breakpoints were analyzed to determine which PCT level corresponded to the highest sensitivity and specificity.

293 patients were included in this single center, retrospective study. The AUC of PCT to predict UTI was 0.717; 95% CI: 0.643–0.791 (p<0.001). A PCT threshold of 0.25ng/ml corresponded to the best combination of sensitivity (67%) and specificity (63%), with a positive predictive value and negative predictive value of 26% and 91%, respectively.

A PCT threshold <0.25ng/ml was a strong predictor of the absence of UTI. The high negative predictive value of PCT may be useful as an adjunct to urinalysis results to rule out UTI and facilitate noninitiation or earlier discontinuation of empiric antibiotics.