A multicenter case-control study of diagnostic tests for urinary tract infection in the presence of urolithiasis

Urinary stone disease (USD) alone can cause much morbidity, but when present in conjunction with urinary tract infection, complications and morbidity increase even more. This study investigated the clinical and laboratory findings in patients who had USD with and without infection and evaluated the most suitable diagnostic value for urinary tract infection parameters before urine culture results were available. In a prospective fashion, patients who presented to the emergency department with a complaint of colicky flank pain (with or without hematuria) and who were diagnosed as having urolithiasis with ultrasound were evaluated for 1 year. The gold standard for the diagnosis of urinary tract infection was urine culture. The most suitable diagnostic value for urinary tract infection parameters was determined by receiver operating characteristic (ROC) curves. Logistic regression was used to identify independent variables that predicted a positive urine culture. Of the 192 eligible patients, 177 agreed to participate in the study. Of the clinical and laboratory characteristics analyzed, urine WBC, blood WBC, and fever were significantly different between culture positive and negative patients (p < 0.001, p = 0.04 p = 0.012, respectively). Using ROC curve analysis, pyuria (over 10 WBCs per HPF), fever over 37.9 degrees C, and leucocytosis over 11,300 were the best predictors of a positive culture result. The logistic regression model for leukocytosis > 11,300 (OR 2.1), pyuria (OR 2.8), and temperature > 37.9 degrees C (OR 3.1) showed a significantly increased risk of having a positive urine culture (correct class 87.9%). While a single physical examination or laboratory finding cannot predict urinary tract infection in USD patients with complete reliability, the presence of pyruria, fever, and leukocytosis significantly increases the odds of a positive urine culture.