Concentration matters in newer urinalysis techniques
In newer urinalysis techniques, concentration matters. In a retrospective study of 27,000 infants aged younger than 3 months evaluated for urinary tract infection (UTI) with paired urinalysis and urine culture, investigators set out to determine the optimal urine white blood cell (WBC) threshold for UTI when using an automated urinalysis system stratified by urine concentration. Based on their analysis of the data, the authors recommend using pyuria thresholds of 3 WBC/high-power field (HPF) in dilute urine (specific gravity, <1.015) and 6 WBC/HPF in concentrated urine (specific gravity, >1.015) for a presumptive diagnosis of UTI. They also note that positive leukocyte esterase by automated dipstick is a strong indicator of UTI (Chaudhari PP, et al. Pediatrics. 2016;138:e20162370).