BERKELEY, CA (UroToday.com) - Overactive bladder (OAB) diagnosis is predominately based on a combination of patient symptoms, with additional information from urodynamics in some patients. Recently the role of biomarkers in overactive bladder has evoked much interest as a way of aiding diagnosis and monitoring disease progression and response to treatment.
A biomarker is an indicator of a particular disease. It is generally used to define the presence (diagnostic biomarker), severity, and progression (prognostic biomarker) of a condition and/or its response to a specific treatment (predictive biomarker). Biomarkers can be specific cells, enzymes, hormones, genes, or gene products, which can be detected and measured in parts of the body such as blood, urine, or tissue. Biomarkers of overactive bladder may play a role in both the clinical assessment and the management of patients, as well as in the research setting.
Urinary biomarkers that have been studied in relation to OAB are nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), prostaglandins, cytokines, and C-reactive protein (CRP). All these biomarkers are thought to have a role in inflammation and/or nerve growth. Inflammation has been proposed to contribute to the pathophysiology of OAB.
On reviewing the current literature, it appears that urinary NGF levels are higher in OAB patients and decrease with effective antimuscarinic and botulinum toxin treatment. However urinary NGF also appears increased in acute bladder inflammation, so conditions such as acute bacterial cystitis and urothelial cell carcinoma should be excluded.
Fewer studies exist on BDNF, however 2 studies carried out in humans demonstrated higher BDNF levels in those with OAB and that treated OAB causes a reduction in BDNF levels.
Prostaglandins are synthesised in the bladder muscle and mucosa and animal studies have shown intravesical instillation of prostaglandins resulted in increased micturition pressure and decreased bladder capacity. However, human studies on prostaglandins reveal conflicting results with some showing them to be increased in OAB and others showing no significant difference in prostaglandin levels between OAB and interstitial cystitis/bladder pain. The role of cytokines and CRP does not appear to be specific to the OAB disease process according to the current available evidence.
Genetic biomarkers have mainly focused on stress incontinence, however the rs4994 single nucleotide polymorphism of the beta3-adrenoreceptor appears to be associated with an almost 2.5-fold increased risk of OAB symptoms.
Based on the evidence so far, NGF and BDNF appear to be the most promising biomarkers in OAB. Although still in their infancy, these neurotrophic factors could potentially diagnose OAB, negate the need for urodynamics, and aid in monitoring disease progression and response to treatment, in addition to clinical symptoms.
Alka A. Bhide, Rufus Cartwright, Vik Khullar, and G. Alessandro Digesu 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.
Department of Urogynaecology, St. Mary's Hospital, Cambridge Wing, Praed Street, W1 1NY, London, UK
Biomarkers in overactive bladder - Abstract