November 2023
Pyuria doesn’t necessarily indicate infection

In a group of healthy older women, some pyuria was normal.

Strong evidence argues against treating asymptomatic bacteriuria in most patients (NEJM JW Gen Med Oct 1 2019 and JAMA Intern Med 2019; 179: 1519-1527). Still, distinguishing asymptomatic bacteriuria from urinary tract infections (UTIs) that do require treatment is tricky, especially among older patients.

Researchers in the Netherlands evaluated urinalysis results obtained from 63 older women (age, 65 years or older; mean age, 78 years) who received diagnoses of UTI based on at least two new-onset symptoms (most often frequency and dysuria), pyuria and culture results. None were catheterised or had substantial cognitive impairment. The analysis expressed urinary white blood cell (WBC) count in cells/mcL; the conversion from cells/mcL to cells/high-power field (HPF) is about 5:1.

Compared with specimens obtained from 101 asymptomatic, age-matched mostly community-dwelling controls, spun urine sediment from UTI patients had significantly more WBCs on automated microscopy – almost 900cells/mcL (about 180cells/HPF). However, the degree of pyuria among controls was considerably higher than anticipated: median WBC cells/mcL ranged from negligible in controls with insignificant culture results to almost 300 (60 cells/HPF) in those in whom asymptomatic bacteriuria was diagnosed because their cultures yielded substantial amounts of a single organism.

Comment: The take-home message of interesting study is not that patients with UTIs have substantial pyuria, but rather that older women with asymptomatic bacteriuria (and even some with no urinary pathology at all) have far more leucocytes in their urine than standard ‘normal’ values allow. The authors point out that normal values for urine parameters are derived from young women’s samples, and they argue that new ‘normal’ values are needed to manage older patients responsibly, especially those with asymptomatic bacteriuria.

Abigail Zuger, MD, Former Associate Clinical Professor of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai; former Senior Attending Physician, Mount Sinai Roosevelt and Mount Sinai St. Luke’s Hospitals, New York City, USA.

Bilsen MP, et al. Current pyuria cutoffs promote inappropriate urinary tract infection diagnosis in older women. Clin Infect Dis 2023; 76: 2070-2076.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine, Hospital Medicine.

Clin Infect Dis