For patients who already have a positive result on a screening test for primary aldosteronism (PA), confirmatory testing with the seated saline suppression test (SSST) adds little to the diagnostic work-up and may delay proper and timely care, according to a study published in the Annals of Internal Medicine.
The SSST may misinform treatment decisions and lead to missed chances for intervention “even in patients who would clearly respond to treatment,” the authors wrote, led by Alexander A. Leung, MD, MPH, Division of Endocrinology and Metabolism, Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
The research setting was the Endocrine Hypertension Clinic in Calgary, and the study included 156 adults with a positive screening result for PA. The SSST involved administering 2 L of 0.9% sodium chloride intravenously over 4 hours.
“The results of our study suggest that removal of routine confirmatory testing from the diagnostic care pathway for PA may help to improve diagnostic accuracy and reduce the time needed for diagnosis and treatment for most patients,” the authors wrote.
Fewer Than 1% of Patients With PA Get Treatment
PA accounts for 10%-30% of all cases of hypertension worldwide. Diagnosing it is important not just because of the prevalence but because there are highly effective, disease-targeted treatments. But fewer than 1% of patients with PA get treatment because of the lack of awareness and barriers raised by a complex diagnostic pathway.
That’s why Leung’s team set out to assess in a blinded clinical trial whether confirmatory testing was worth the complications it added to the process.
“We selected the SSST because many believe it to be the most reliable confirmatory test for PA,” the authors wrote. “We used response to targeted treatment as the reference because it is pragmatic and relevant to patients.”
They found that “the SSST could not discriminate between response statuses (area under the curve, 62.1%; 95% CI, 45.1%-79.1%). The positive and negative likelihood ratios were equivocal for aldosterone cutoffs ranging from 140 to 300 pmol/L. These findings remained consistent after differences in treatment, occurrence of hypokalemia, and laboratory assay used were accounted for.”
‘Limited Application in the US’
However, Joshua D. Lenchus, DO, RPh, internal medicine specialist and American Osteopathic Association board member, who was not part of the study, said the study “likely has relatively limited application in the US.”
He explained that some patients with suspected primary PA do not require a confirmatory test, and of those currently available, the SSST is not universally applicable.
“For example, it is generally not used in patients with uncontrolled blood pressure or those with a history of congestive heart failure. Running an intravenous infusion of saline over 4 hours is easier in an inpatient setting but may be cumbersome in an outpatient office,” he told Medscape Medical News.
He said he was also surprised to find that “less than 30% of study participants had resistant hypertension, less than 15% were under the age of 40, and more than 50% were over the age of 60. Typically, the incidence rate of primary aldosteronism is highest in females under 40 years of age with resistant hypertension and hypokalemia.”
Lenchus said the SSST is one of several confirmatory tests for PA used in the United States, including the captopril challenge test and the fludrocortisone suppression test, although no gold standard exists as yet.
He said he would like to see a follow-up with a larger cohort of patients, perhaps comparing several confirmatory tests head-to-head to identify a standard.
The study was funded by the Canadian Institutes of Health Research, Hypertension Canada, and the Heart and Stroke Foundation of Canada.
Marcia Frellick is a Chicago-based healthcare journalist.
