Urine concentration should be taken into account when interpreting pyuria in infants.

Commentary on:  Chaudhari PP, Monuteaux MC, Bachur RG, et al . Urine concentration and pyuria for identifying UTI in infants. Pediatrics 2016;138:e20162370. The relationship between pyuria and true urinary tract infection (UTI) remains controversial. Most studies have assessed pyuria using manual microscopy in centrifuged urine. However, standard practice at most centres now involves automated urinalysis of uncentrifuged urine, thus pyuria in dilute samples may have more significance than pyuria in concentrated urine samples. It may therefore be important to consider the possible impact of urine concentration on the significance of white cell counts (WCC) or leucocyte esterase (LE) assessment. This was a retrospective study of routinely collected data from infants aged less than 3 months with suspected UTI, who presented to a busy US emergency department (ED) over 5 years. Automated urinalysis and culture were available for each eligible child. UTI was defined as ≥50 000 colony-forming units (CFU)/mL of a pathogenic organism, and all analysed samples were collected by catheter. Dipstick urinalysis was automated …