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We should use a much higher leukocyte cutoff to diagnose UTI in older women
Clinical Question
What is the optimal leukocyte cutoff for diagnosing urinary tract infection in older women?
Bottom line
For women 65 years and older, we should use a much higher cutoff for pyuria before diagnosing UTI to avoid overtreating women who have asymptomatic bacteriuria. A limitation of this diagnostic case-control design is that it tends to overestimate the accuracy of a test, so a follow-up study using a cohort design and women with clinically suspected UTI should be done next. (LOE = 4)
Overuse alert: This POEM aligns with the Canadian Nurses Association’s Choosing Wisely Canada recommendation: Don’t recommend antimicrobials to treat bacteriuria in older adults unless specific urinary tract symptoms are present. A patient handout is also available on reducing unnecessary antibiotic use.
Reference
Study design: Diagnostic test evaluation
Funding: Government
Setting: Outpatient (any)
Synopsis
The usual cutoffs for diagnosing urinary tract infection (UTI) are greater than 10 leukocytes/microliter (mcl) or greater than 5 to 10 leukocytes/high-powered field. However, these cutoffs were derived from studies of premenopausal women. Approximately 20% of older women have asymptomatic bacteriuria (ASB), and 90% of them also have some degree of pyuria. To identify the optimal leukocyte cutoff for a diagnosis of UTI in older women, these researchers identified 63 women, 65 years and older, with UTI based on a positive urine culture for a uropathogen, at least 2 lower urinary tract symptoms (LUTS), and at least 10 leukocytes/mcl. The comparison group consisted of 101 community-dwelling women, 65 years or older, without LUTS; 18 had ASB, 25 had a negative urine culture, and 58 had a culture with mixed flora. All urine samples underwent automated microscopy and urine flow cytometry. The area under the curve for leukocytes as a test for UTI was 0.93 for both methods. The optimal cutoff for automated microscopy was greater than 265 leukocytes/mcl, which was 88% sensitive and 88% specific (positive likelihood ratio [LR+] 7.2; negative likelihood ratio [LR-] 0.14). For flow cytometry, the optimal cutoff was greater than 231 leukocytes/mcl, which was 91% sensitive and 86% specific (LR+ 6.5; LR- 0.10). And what about the cutoff of greater than 10 leukocytes/mcl? It was 100% sensitive, but only 36% specific.
Reviewer
Mark H. Ebell, MD, MS
Professor
University of Georgia
Athens, GA
Comments
Diagnosing UTI
Should physicians in community-based practice still count leukocytes using microscopy, as a test for UTI? I diagnose based on clinical findings, or wait for a culture report.
Thresholds for UTI in elderly females
This confirms what Urologists have long known
Impact assessment
Excellent
LEUKOCYTS AND UTI IN OLDERWOMEN
GOOD TO KNOW