Review of Recent Literature: Interstitial Cystitis and Urinary Markers - by Peter M. Lotze, M.D.
Recently, Dr. Kenneth Powers wrote an article for urogyn update reviewing urinary markers in the Painful Bladder Syndrome (PBS). In the article, Dr. Powers recognized that the diagnosis of Interstitial Cystitis (IC) as defined by the NIDDK is restrictive and may exclude as many as 60% of patients who have Interstitial Cystitis from being diagnosed with the disease. In 2002, the diagnosis of “Painful Bladder Syndrome” (PBS) was developed and requires only symptoms of bladder pain when the bladder is being filled as a means to make the diagnosis. However, because PBS does not require cystoscopy (unless hematuria is present) it should be noted that patients complain of bladder pain could also have gynecologic, neurologic, myogenic, or GI problems as well.
The potassium chloride challenge test as well as cystoscopy had been cornerstones for attempting to diagnosis interstitial cystitis but do not provide the highest degree of accuracy of absolutely confirming the diagnosis. Recently, interest has turned to the possible use of “biomarkers” to improve the accuracy of diagnosing people with PBS.
These markers may include the following:
• Inflammatory mediators – elevated levels of histamine and its major metabolite methylhistamine having seen some but not all patients with interstitial cystitis. In addition, Interleukin-6 (IL-6) is a compound that can be found in excess amounts in patients with interstitial cystitis. Individually, neither of these compounds can consistently identify patients with interstitial cystitis. However when both markers are combined, the chances of identifying a person with interstitial cystitis may be as high as 70%.
• Proteoglycans – GP-51 is a glycoprotein that can be found in the bladder. In patients with PBS, GP-51 is found in low volumes compared to patients with other inflammatory bladder conditions (e.g. bladder infections). Following hydrodistention, GP-51 appears to be secreted in excess amounts. Still, as a marker for diagnosing the disease, GP-51 remains relatively nonspecific as a diagnostic test.
• Proliferative factors – a urinary marker called antiproliferative factor is produced by the cells lining the bladder with PBS and prevents the normal growth of the cells lining the bladder. As a marker, APF has been found to have good accuracy in identifying PBS patients (94% sensitivity/95% specificity). However, as a marker, it has not been able to accurately predict treatment responses. Still, the widespread clinical application of APF as a diagnostic marker is unclear at this time. This is partly due to a lack of universally excepted criteria for how the diagnosis is made.
The use of urinary markers to diagnosis painful bladder syndrome is not generally recommended at this time but research through these biomarkers may lead to the potential development of new therapies in the future. In the meantime, Painful Bladder Syndrome remains a diagnosis of exclusion.
Reference Urinary Markers and Painful Bladder Syndrome by Kenneth Powers, MD. Urogyn update (Volume 27, No. 2, Pages 1, 6-7) 2008.
Peter M. Lotze, M.D., PURE HOPE Medical Advisory Board Chairperson
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