NEW YORK (Reuters Health) - The potassium sensitivity test can predict the response of interstitial cystitis patients to treatment with glycosaminoglycan-substitution therapy, according to a report in the November BJU International.

Glycosaminoglycan-replacement therapies are increasingly used in the treatment of interstitial cystitis, the authors explain, but the results are variable and the outcome unpredictable.

Dr. Suresh K. Gupta and colleagues from Arrowe Park Hospital, Merseyside, UK investigated whether the potassium sensitivity test (PST) could predict the response to treatment with intravesical sodium hyaluronate in 38 patients with interstitial cystitis or chronic pelvic pain of unknown origin.

Seventeen of 23 patients (74%) with a positive PST experienced a significant clinical improvement after treatment, the authors report, compared with three of 13 patients with a negative PST (23%).

Both groups experienced improvements in a self-administered interstitial cystitis symptom index, but only patients with a positive PST experienced significant improvements in the problem index, the report indicates. All improvements were greater in the positive PST group.

There were no major complications from treatment, the researchers note.

"The obvious implication is that the PST can identify a subgroup of patients with interstitial cystitis who have predominantly an abnormality of the bladder epithelium," the investigators explain. "The epithelial abnormality might be caused by defective glycosaminoglycan, which forms a barrier to prevent urine and bladder contents leaking into the urothelium and damaging underlying muscle and nerves."

"The present study shows that glycosaminoglycan-replacement therapy can be selectively offered to patients based on the result of their PST," the authors conclude. "However, the treatment should not be completely withheld from patients with negative PST, as some patients would benefit from this despite a negative test, as in the present study."

"We suggest that [PST-negative] patients with intractable symptoms can be offered this treatment as long as they understand that the chances of a successful outcome are much lower," the researchers add.

BJU International 2005;96:1063-1066

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