The Potassium Sensitivity Test (PST) involves inserting a solution of a known irritant into the bladder, for the ostensible purpose of diagnosing interstitial cystitis. While it is still used by some urologists, the American Urological Association (AUA) has deemed it ineffective and unnecessarily painful to patients.
"In addition, the PST is painful and risks triggering a severe symptom flare. In view of the paucity of benefits, the panel agreed the risk/benefit ratio was too high for routine clinical use." -AUA IC Guidelines, 2014
This test was based on the myth that interstitial cystitis is a direct result of damage to the bladder lining (while we now know that IC is multi-factorial and in many cases the bladder is an ‘innocent bystander’ in the process). The theory was that inserting an extreme irritant into the bladder would be able to immediately identify patients who had damage to the bladder lining.
There are three important aspects of any diagnostic test, but the Potassium Sensitivity Test fails on all three of these key points:
1. Does it correctly identify people who have the condition?
Studies have shown the PST does not identify 26-40% of patients who have IC - and remember, these are patients who are already presenting with all the symptoms of IC. Simply diagnosing IC by the symptoms that are present would be far more accurate than mis-identifying more than one-quarter of patients.
As the AUA Guidelines state: “A negative test will not change the clinical plan, because 26% of patients who met the strict NIDDK criteria for IC/BPS had a negative test.”
2. Does it rule out people who don't have the condition?
The Potassium Sensitivity Test also has many false positives with other conditions, including urinary tract infections, overactive bladder, and bladder cancer. These are also the most likely explanations (other than IC) for the symptoms that patients experience, so the inability to differentiate between these other conditions renders the test ineffective.
The IC Guidelines state: "The potassium sensitivity test (PST) does not result in the identification of other disorders. In fact, it is consistently positive in some alternate disorders."
3. Does it change the treatment plan?
The results of the Potassium Sensitivity Test don't have any affect on the treatment plan for interstitial cystitis. If the test is positive, a patient would begin standard IC treatments immediately. If it's negative, they might have some additional tests, but would hopefully still be correctly diagnosed. The PST also doesn't predict the success of any specific treatment (like Elmiron or bladder instillations), so it can't guide which treatment options will be most successful.
The AUA Guidelines report "the evidence to date reveals minimal predictive value [of the Potassium Sensitivity Test]."
In fact, no test or procedure is necessary to diagnose interstitial cystitis – it is diagnosed by the symptoms and in the absence of other identifiable causes. A cystoscopy is often done to either discover Hunner’s lesions or rule out other conditions, but is not technically required for a diagnosis.
If your doctor recommends conducting a Potassium Sensitivity Test, they may have an outdated understanding of the condition. You can ask them to review the American Urological Association IC Guidelines, or you may want to get a second opinion before moving forward with an unnecessary and painful test.
Dr. Nicole Cozean is the founder of PelvicSanity physical therapy, Orange County's premier pelvic floor physical therapy clinic. One of only 270 PTs to be board-certified in the pelvic floor, and the first PT to serve on the ICA Board of Directors, Nicole is the author of the acclaimed and best-selling book The Interstitial Cystitis Solution (2016). She is an adjunct professor at her alma mater, Chapman University. The PelvicSanity blog focuses on presenting practical, positive information to help patients beyond the walls of Nicole's clinic.