Urinary tract infection in febrile infants younger than eight weeks of age

Objective. To assess the usefulness of laboratory parameters, including per ipheral white blood cell (WBC) count, C-reactive protein (CRP) concentratio n, erythrocyte sedimentation rate (ESR), and microscopic urinalysis (UA), f or identifying febrile infants younger than 8 weeks of age at risk for urin ary tract infection (UTI), and comparison of standard UA and hemocytometer WBC counts for predicting the presence of UTI. Methods. A total of 162 febrile children <8 weeks of age were enrolled in t his prospective study. All underwent clinical evaluation and laboratory inv estigation, including WBC count and differential; ESR; CRP; blood culture; a lumbar puncture for cell count and differential, glucose level, protein l evel, Gram stain, and culture; and a UA and urine culture. All urine specim ens were obtained by suprapubic aspiration and microscopically analyzed wit h standard UA as well as with hemocytometer WBC counts. Quantitative urine cultures were performed. Sensitivity, specificity, accuracy, likelihood rat ios, and receiver operating characteristic (ROC) curves were determined for each of the screening tests. Results. There were 22 positive urine culture results of at least 100 colon y-forming unit/mL. Eighteen of these 22 patients were males, and all were u ncircumcised. There were significant differences for pyuria greater than or equal to 5 WBCs/ hpf, pyuria greater than or equal to 10 WBC/mu L, CRP >20 mg/L, and ESR >30 mm/hour between culture-positive and culture-negative gr oups (P < .05). The ROC area for hemocytometer WBC count, standard UA, peri pheral WBC count, ESR, and CRP concentration were .909 +/- .045, .791 +/- . 065, .544 +/- .074, .787 +/- .060, and .822 +/- .036, respectively. The ROC curve analysis indicates that the CRP, ESR, and standard UA were powerful but imperfect tools with which to discriminate for UTI in potentially infec ted neonates. Hemocytometer WBC counts had the highest sensitivity, specifi city, accuracy, and likelihood ratios for identifying very young infants wi th positive urine culture results. For all assessments, hemocytometer WBC c ounts were significantly different, compared with the standard urinalysis. ESR, CRP, and peripheral WBC counts were not helpful in identifying UTI in febrile infants. Conclusion. UTI had a prevalence of 13.6% in febrile infants <8 weeks of ag e. The CRP, ESR, and standard UA were imperfect tools in discriminating for UTI, and the sensitivity of these laboratory parameters was relatively low . Hemocytometer WBC count was a significantly better predictor of UTI in fe brile infants.