New Screening Test for Aldosteronism

An Expert Interview With Jeff Shih-chieh Chueh, MD, PhD

Emma Hitt

June 19, 2012

June 19, 2012 (Atlanta, Georgia) — Editor's note: A new screening test for primary aldosteronism that uses a ratio of potassium excretion capacity/body mass index is as good as the aldosterone/renin ratio in terms of its screening power for primary aldosteronism, according to the findings of a study presented here at the American Urological Association (AUA) 2012 Annual Scientific Meeting.

Medscape Medical News spoke with lead investigator Jeff Shih-chieh Chueh, MD, PhD, from the Cleveland Clinic, Charleston Urology Office, in West Virginia, about his team's findings.

Medscape: Can you describe the study findings that you presented at the AUA meeting?

Dr. Chueh: Current screening approaches using the aldosterone/renin ratio (ARR) are costly and not universally available. Our study evaluated the ability of the potassium excretion capacity (PUKC)/body mass index (BMI) ratio to screen for primary aldosteronism (abstract 42). PUKC is defined as the serum potassium to urine potassium clearance ratio.

We looked at 134 patients known to have primary aldosteronism and 43 patients with essential hypertension. A comparison of receiver operating characteristic curves showed that the PUKC/BMI and ARR ratios were similar for each method (95% confidence interval, –0.029 to 0.183; P = .186). I think with our study we proved that the efficacy of this test is about the same as ARR, the current gold-standard screening test.

Medscape: What is the advantage of using the PUKC/BMI ratio?

Dr. Chueh: First of all, primary aldosteronism is a cause of secondary hypertension, and this kind of hypertension is treatable. The most important thing is to diagnose it early, which will be easier using this ratio. We currently use the ARR ratio to try to screen for this disease, but this test is more expensive and is not available in every lab. Most of the time, a community hospital will need to mail out a sample to measure the ARR ratio, and it takes a week or 2 for the test to come back. But the PUKC/BMI ratio test we propose measures the electrolytes in the blood, and as long as you have a lab available — even in a small town — it can be done. So our test is more accessible and you can get the result back faster.

Medscape: Can this test be used in clinical practice now?

Dr. Chueh: Our study is limited in that it is retrospective, and we need to confirm these results in a prospective study. At this moment the test is usable, but if the results can be confirmed in a prospective study, the test can replace the ARR.

Medscape: Are there any patients for whom the PUKC/BMI ratio couldn't be used or wouldn't be as useful?

Dr. Chueh: In our study population, we did not see any special limitations with the PUKC/BMI ratio. In addition, the PUKC/BMI ratio gives us better screening ability than either PUKC or BMI alone.

Medscape: Were there any other studies of aldosteronism presented at the AUA meeting?

Dr. Chueh: Another study from our group compared adrenalectomy and medical therapy with spironolactone — I think the findings were really interesting (abstract 43). In patients with aldosterone-producing adenomas, the choice between surgery and spironolactone remains unclear, so we compared the 2. In our study, 66 patients underwent adrenalectomy and 34 patients received spironolactone drug therapy. Both groups of patients improved on several parameters, including blood pressure and potassium levels, compared with baseline values; however, patients undergoing surgery had better outcomes with respect to kidney function, including a significant decrease in proteinuria and in cystatin C–based estimation of glomerular filtration rate.

Medscape: Why are these findings important?

Dr. Chueh: Both approaches are thought to produce similar outcomes with respect to lowering blood pressure and decreasing serum potassium levels. We expected surgery and medical therapy outcomes to be the same, but we saw that surgery resulted in better long-term kidney function than medical therapy with spironolactone. Prior to these study results, we might have been more inclined to leave patients on medication, but these results suggest that as long as patients can tolerate anesthesia, it is best to have surgery to remove the adrenal adenoma.

American Urological Association (AUA) 2012 Annual Scientific Meeting: Abstracts 42 and 43. Presented May 19, 2012.

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