Useful Predictive Factors for Bacteremia among Outpatients with Pyelonephritis

OBJECTIVE: The aim of this study was to identify predictive factors for bacteremia conveniently and quickly among outpatients diagnosed with pyelonephritis. PATIENTS: All patients who were diagnosed with pyelonephritis at the outpatient clinic in the Department of General Medicine of Juntendo University Hospital from April 1, 2008, to June 30, 2015, were enrolled. Patients from whom blood cultures had not been taken were excluded. METHODS: Clinical information was extracted from medical charts. Factors potentially predictive of bacteremia were analyzed using a t-test and Fisher's exact test, followed by a multivariable logistic regression model analysis. RESULTS: Blood cultures were drawn from 116 patients, and 25 (22%) presented with bacteremia. A multivariate analysis with the age, chills, platelet count and urine nitrite test results revealed that older age, positive urinary nitrite test results and chills tended to be associated with bacteremia, respectively. [older age: unit odds ratio (OR) 1.02, p=0.052, 95% confidence interval (CI) 1.00-1.05, positive urinary nitrite test findings: OR 2.5, p=0.092, 95% CI 0.86-7.7, chills: OR 2.5, p=0.096, 95% CI 0.84-7.65]. The area under the receiver operating characteristic (ROC) curve of this model was 0.77. Regardless of age, positive urinary nitrite test findings were significantly associated with bacteremia (OR 3.1, p=0.033, 95% CI 1.1-9.2), and chills tended to be associated with bacteremia (OR 2.7, p=0.07, 95% CI 0.93-7.9) The area under the ROC curve of this model was 0.75. CONCLUSION: Bacteremia should be considered in pyelonephritis patients with rapidly assessable factors in outpatient clinic. In particular, a model including a urinary nitrite test has the potential to aid in the prediction of bacteremia.