For women with overactive bladder syndrome, urinary ATP may be a dynamic biomarker of detrusor overactivity, "Beyond the Abstract," by Miguel Silva-Ramos and Paulo Correia-de-Sá

BERKELEY, CA (UroToday.com) - The bladder is often said to be an unreliable witness, since the relation between symptoms and urodynamic findings is weak. Urodynamic investigations are also far from accurate, creating a need to develop more reliable, non-invasive tests to assess overactive bladder (OAB) patients. In recent years we’ve witnessed an enthusiastic search for biomarkers of OAB with this purpose.

There is today a considerable amount of evidence showing a paramount role of adenosine triphosphate (ATP) on bladder function and particularly in the pathophysiology of detrusor overactivity. Several studies support the theory that the urothelium releases ATP in response to stretch, and that this ATP can act on suburothelial nerves conveying sensory information to the central nervous system. There is also evidence that the urothelium from OAB patients and from obstructed bladders releases more ATP than controls.

We hypothesised that ATP could be measured in urine, and patients with detrusor overactivity should have higher ATP concentration than controls.

We recruited 70 women, 34 patients with OAB symptoms and detrusor overactivity and 36 controls. Urinary samples from 2 consecutive voids were immediately freeze preserved and afterwards used to measure ATP, nerve growth factor (NGF), and creatinine.

Urinary ATP levels were significantly (p < 0,05) higher in OAB patients compared to controls: 2647±403pM vs 7004±1228pM in the first void and 5700±978 pM vs 10577±1533 pM in the second void. This was also demonstrated when ATP content was normalized to creatinine levels and voided volume. Interestingly there was a direct correlation between voided volume and urinary ATP; this could explain why urinary ATP levels increased in the second void after drinking water at libitum, since the voided volume was higher in the second void. No statistically significant difference was found in the concentration of NGF between patients and controls. Furthermore, we constructed ROC curves for ATP/creatinine and NGF/ creatinine, and revealed an area under the curve of 0,7407 (95%CI 0,62 to 0,86) and 0,5391 (95%CI 0,39 to 0,69), respectively. We also found a relationship between OAB severity and ATP levels, i.e. patients with OAB wet and low mean voided volume had significantly higher ATP levels.

These results further support the role of ATP in the pathogenesis of detrusor overactivity, and reveal ATP as a highly-sensitive dynamic biomarker of detrusor overactivity in women with OAB syndrome.

Written by:
Miguel Silva-Ramos,a, b and Paulo Correia-de-Sáa as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

aLaboratório de Farmacologia e Neurobiologia, UMIB, Instituto de Ciências Biomédicas Abel Salazar (ICBAS) - Universidade do Porto (UP)
bServiço de Urologia, Centro Hospitalar do Porto (CHP), Porto, Portugal

Urinary ATP may be a dynamic biomarker of detrusor overactivity in women with overactive bladder syndrome - Abstract

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