The Diagnosis of UTI: Concentrating on Pyuria

* Abbreviations: AB — : asymptomatic bacteriuria LE — : leukocyte esterase UTI — : urinary tract infection WBC — : white blood cell The term “pyuria” literally means “pus in the urine” but, in common usage, the focus is not on the presence of pus but on the number of white blood cells (WBCs) or amount of leukocyte esterase (LE) that exceeds a threshold and suggests a urinary tract infection (UTI). In this issue of Pediatrics , Chaudhari et al1 share the results of a study of the impact of urine concentration on the optimal threshold in the new era of automated urinalysis. Centrifugation of urine specimens has long been standard laboratory practice, presumably performed to concentrate sediment and facilitate the detection of cellular elements and bacteria. The implied (but questionable) assumption is that the process renders 1 spun specimen comparable to another in concentration. The “enhanced urinalysis”2 and automated urinalysis methods use analysis of unspun urine for cellular elements but have not attempted to control for concentration. The authors recognized concentration as a potential concern and demonstrated, with automated urinalysis, different thresholds for dilute and … Address correspondence to Kenneth B. Roberts, MD, 3500 Bramblewood Dr, Mebane, NC 27302. E-mail: kenrobertsmd{at}gmail.com