BERKELEY, CA (UroToday.com) - Despite its high prevalence and economic burden, there is still no cure for overactive bladder (OAB) syndrome or objective tests for its diagnosis.
Recently, Wennberg et al. provided evidence supporting a dynamic progression of OAB symptom severity over time. Over a 16-year period (1991–2007), the proportion of women with OAB without urgency urinary incontinence (OAB dry) did not differ significantly (1991, 11%; 2007, 10%); however, the number of women with OAB with urgency urinary incontinence (OAB wet) increased from 6% to 16%. Among women with OAB dry in 1991, 23% remained OAB dry and 28% reported symptom progression to OAB wet in 2007. Among women who were OAB wet in 1991, 53% remained OAB wet and 21% reported symptom regression to OAB dry in 2007. The rate of complete remission of OAB symptoms was greater for women who were OAB dry (49%) compared with those who were OAB wet (26%). Another study by Malmsten et al. in men with OAB provided similar results. Although some evidence suggests differences in the progression of OAB and urinary incontinence according to gender and age, further studies are needed to assess risk factors for symptom progression and regression or remission.
Biomarkers constitute objective measurable indicators of biological conditions. Detrusor overactivity (DO) has been the classic biomarker used in OAB, assessed urodynamically, with clear-cut limitations. In fact, urodynamics is an invasive exam and does not necessarily aid in the diagnosis of OAB, as approximately half of the patients do not present DO and many asymptomatic individuals do. Additionally, the hallmark symptom of OAB is urgency, which is difficult to perceive for patients and caregivers. Therefore, OAB diagnosis is not easily undertaken and there is a clear need for more efficient tools to diagnose this condition and monitor treatment efficacy. In addition, studies of disease progression might be aided by the use of biomarkers, such as urinary cytokines, chemokines, and growth factors. Urinary levels of these inflammatory mediators are elevated in patients with idiopathic OAB, suggesting a role of inflammation in the pathology of OAB.
Despite the recent wide research on ultrassonographic measure of detrusor wall thickness, this technique remains unreliable, and further standardization is required for diagnostic purposes. From the current putative urinary biomarkers, neurotrophins appear as the most promising. Recent studies reported high urinary levels of nerve growth factor (NGF) in OAB patients, suggesting it may be used as a potential biomarker. However, the sensitivity of this possible diagnostic tool is hindered by a significant overlap between urinary NGF concentration in patients and healthy individuals. Auspiciously, preliminary results suggest that brain-derived neurotrophic factor (BDNF) may constitute a more efficient OAB biomarker, with little overlay between urinary concentrations in OAB patients and healthy individuals and a good correlation with the severity of symptoms. Interestingly, a BDNF val66met polymorphism has been associated with depression, one of the most prevalent psychiatric disorders, frequently associated with OAB. Ultimately, neurotrophins will contribute to elucidate the physiopathological basis of OAB. The genetic basis of OAB is likely to involve the interaction of multiple genes, reflecting the complexity this dysfunction. The first genome-wide association studies for OAB are in progress and should identify new susceptibility genes and discriminate different pathophysiological variants of OAB.
Much remains to be investigated in OAB, not only to clarify its pathophysiology, but also to develop objective, noninvasive and reliable diagnostic tools. This has been the major drive of many research teams in this field, the detection and clinical application of emerging OAB biomarkers.
Tiago Antunes-Lopes 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.