ATP Nixed for Assessing Urinary Infection
BARCELONA—Urinary adenosine- 5' triphosphate (ATP) apparently has no role as a diagnostic tool in patients with lower urinary tract symptoms (LUTS), according to data reported by a British group at the 43rd Annual Meeting of the International Continence Society.
“We found that urinary ATP disappoints as a potential surrogate, clinical diagnostic marker of urinary infection in patients with LUTS,” James Malone-Lee, MD, Professor of Medicine at University College London Medical School, and associates said in a poster presentation. “In fact, urinary ATP, when used alone, does not improve on current diagnostic markers of urinary tract infection such as urine microscopy.”
Their study examined the effects of age, gender, symptoms, pyuria, and midstream urine culture on urinary ATP.
The exclusion of urinary tract infection (UTI) is a “mandatory first step” in patients with LUTS, the authors said. In individuals who present with the classic symptoms of acute frequency and dysuria, the diagnosis of UTI is not difficult to establish. However, in those with LUTS, clinicians rely on dipstick tests and MSU cultureto rule out possible infection.
Despite their widespread use, the midstream urine culture and urinary dipstick are inadequate for excluding UTI in patients with LUTS symptoms but without acute frequency and dysuria, they added.
The best marker currently available for UTI is microscopy of a fresh, unspun urine sample, which reportedly has a nearly 70% sensitivity rate. Patient clinics, however, often do not have the means to analyze urine samples promptly, and delayed analysis of a urine sample may produce a false-negative result. Thus, there is a need to identify other surrogate urinary markers that can be used clinically, Dr. Malone-Lee and his colleagues said.
ATP is a neurotransmitter and inflammatory cytokine implicated in the pathophysiology of lower urinary tract disease. It is used in the food, water hygiene, and sanitation industry as a marker of bacterial contamination. Urinary ATP has been proposed as a clinical test and surrogate marker of urinary tract infection.
For the study, 340 patients presenting with LUTS were recruited over a two-month period from incontinence clinics, and clean-catch midstream urine samples were obtained. Seventy-five healthy control volunteers were recruited from hospital staff.
Urinary ATP was assayed by the conventional luciferin-luciferase method, and pyuria was counted by microscopy of fresh, spun urine. Symptoms were assessed using validated scales.
The study included 100 LUTS patients who were classified as being without pyuria, 120 LUTS patients with pyuria, 120 LUTS patients with pyuria, and 75 controls.
The statistical analysis showed that the urinary ATP was very unlikely to explain any more of the disease activity than that achieved by current tests. This was confirmed by analysis of the sensitivity and specificity in relation to current accepted gold-standards.
The investigators said that their results underscore the need for additional research to find other surrogate markers of urinary infection in order to exclude urinary tract infection in patients who present with LUTS.