IS URINE CULTURE NECESSARY TO RULE OUT URINARY-TRACT INFECTION IN YOUNG FEBRILE CHILDREN

Objective. To determine whether the absence of pyuria on the enhanced urinalysis can be used to eliminate the diagnosis of urinary tract inf ection, avoiding the need for urine culture and sparing large health c are expenditures. Design. Results of an enhanced urinalysis (hemocytom eter counts and interpretation of Gramstained smears) performed on unc entrifuged urine specimens obtained by catheter were correlated with u rine cultures in young febrile children at the Children's Hospital of Pittsburgh Emergency Department. In a group of 4253 chil dren (95% feb rile) less than 2 years of age, pyuria was defined as greater than or equal to 10 white blood cells/mm(3), bacteriuria as any bacteria on an y of 10 oil immersion fields in a Gram-stained smear and a positive cu lture as greater than or equal to 50 000 colony-forming units/ml. A su bgroup of 153 children with their first diagnosed urinary tract infect ion were enrolled in a separate treatment trial, acute phase reactants (peripheral white blood cell count, erythrocyte sedimentation rate an d C-reactive protein) were obtained and Tc-99-dimercaptosuccinic acid renal scans were performed. Results. The presence of either pyuria or bacteriuria and the presence of both pyuria and bacteriuria have the h ighest sensitivity (95%) and positive predictive value (85%), respecti vely, for identifying positive urine cultures. Because a white blood c ell count in a hemocytometer is the technically simpler component of t he enhanced urinalysis, we chose to analyze the false negative results and achievable cost savings of using pyuria alone as the sole criteri on for omitting urine cultures. If in this study urine cultures had be en performed only on specimens from children who had pyuria or were ma naged presumptively with antibiotics, cultures of 2600 (61%) specimens would have been avoided. Twenty-two of 212 patients with positive uri ne cultures would not have been identified initially. However, based o n interpretation of acute phase reactants, initial Tc-99-dimercaptosuc cinic acid scan results, response to management and incidence of renal scarring 6 months later, 14 of the 22 patients most likely had asympt omatic bacteriuria and fever from another cause. The remaining 8 patie nts probably had early urinary tract infection. Conclusions. The analy sis of urine samples obtained by catheter for the presence of signific ant pyuria (greater than or equal to 10 white blood cells/mm(3)) can b e used to guide decisions regarding the need for urine culture in youn g febrile children.