Pyuria Thresholds in UTI Diagnosis

HealthDay News—For infants undergoing microscopic urinalysis as part of urinary tract infection (UTI) evaluation, urine concentration should be included in the interpretation, according to a study published online in Pediatrics.

Pradip P. Chaudhari, MD, from Boston Children’s Hospital, and colleagues conducted a retrospective cross-sectional study involving 2,700 infants aged younger than 3 months (median age, 1.7 months) evaluated for UTI in the emergency department with paired urinalysis and urine culture.

The researchers found that the prevalence of UTI was 7.8%. Optimal white blood cell (WBC) cut-points were 3 and 6 WBC per high-power field (HPF) in dilute and concentrated urine, respectively. Regardless of urine concentration, positive leukocyte esterase (LE) had excellent test characteristics for dipstick analysis.

“Urine concentration should be incorporated into the interpretation of automated microscopic urinalysis in young infants. Pyuria thresholds of 3 WBC/HPF in dilute urine and 6 WBC/HPF in concentrated urine are recommended for the presumptive diagnosis of UTI,” the authors write. “Without correction of specific gravity, positive LE by automated dipstick is a reliably strong indicator of UTI.”

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  1. Chaudhari PP, Monuteaux MC, Bachur RG. Urine concentration and pyuria for identifying UTI in infants. Pediatrics. 2016. doi: 10.1542/peds.2016-2370
  2. Roberts KB. The diagnosis of UTI: concentrating on pyuria. Pediatrics. 2016. doi: 10.1542/peds.2016-2877