Dipstick screening for urinary tract infection in febrile infants

OBJECTIVE: This study compares the performance of urine dipstick alone with urine microscopy and with both tests combined as a screen for urinary tract infection (UTI) in febrile infants aged 1 to 90 days. METHODS: We queried the Intermountain Healthcare data warehouse to identify febrile infants with urine dipstick, microscopy, and culture performed between 2004 and 2011. UTI was defined as .50 000 colonyforming units per milliliter of a urinary pathogen. We compared the performance of urine dipstick with unstained microscopy or both tests combined ("combined urinalysis") to identify UTI in infants aged 1 to 90 days. RESULTS: Of 13 030 febrile infants identified, 6394 (49%) had all tests performed and were included in the analysis. Of these, 770 (12%) had UTI. Urine culture results were positive within 24 hours in 83% of UTIs. The negative predictive value (NPV) was .98% for all tests. The combined urinalysis NPV was 99.2% (95% confidence interval: 99.1%-99.3%) and was significantly greater than the dipstick NPV of 98.7% (98.6%- 98.8%). The dipstick positive predictive value was significantly greater than combined urinalysis (66.8% [66.2%-67.4%] vs 51.2% [50.6%- 51.8%]). These data suggest 8 febrile infants would be predicted to have a false-positive combined urinalysis for every 1 infant with UTI initially missed by dipstick screening. CONCLUSIONS: Urine dipstick testing compares favorably with both microscopy and combined urinalysis in febrile infants aged 1 to 90 days. The urine dipstick test may be an adequate stand-alone screen for UTI in febrile infants while awaiting urine culture results.