Confirmatory testing in primary aldosteronism: extensive medication switching is not needed in all patients

Abstract

Objective: Confirmatory testing of suspected primary aldosteronism (PA) requires an extensive medication switch that can be difficult for patients with severe complicated hypertension and/or refractory hypokalemia. For this reason, we investigated the effect of chronic antihypertensive medication on confirmatory testing results. To allow the results to be interpreted, the reproducibility of confirmatory testing was also evaluated.

Design and methods: The study enrolled 114 individuals with suspected PA who underwent two confirmatory tests. The patients were divided into two groups. In Group A, both tests were performed on the guidelines-recommended therapy, i.e. not interfering with the renin-angiotensin-aldosterone system. In Group B, the first test was performed on chronic therapy with the exclusion of thiazides, loop diuretics, and aldosterone antagonists; and the second test was performed on guidelines-recommended therapy. Saline infusion, preceded by oral sodium loading, was used to suppress aldosterone secretion.

Results: Agreement in the interpretation of the two confirmatory tests was observed in 84 and 66% of patients in Groups A and B respectively. For all 20 individuals in Group A who ever had end-test serum aldosterone levels ≥240 pmol/l, aldosterone was concordantly nonsuppressible during the other test. Similarly, for all 16 individuals in Group B who had end-test serum aldosterone levels ≥240 pmol/l on modified chronic therapy, aldosterone remained nonsuppressible with guidelines-recommended therapy.

Conclusion: Confirmatory testing performed while the patient is on chronic therapy without diuretics and aldosterone antagonists can confirm the diagnosis of PA, provided serum aldosterone remains markedly elevated at the end of saline infusion.

Figure 1

Study protocol. Flowchart describes the study protocol in brief, including the study procedures and the patients excluded from the analysis. *Denotes a therapy with no or minimal effect on the RAAS, only doxazosin and/or verapamil were allowed. ^†Only amiloride was permitted at a dose not exceeding 15 mg/day.

Figure 2

Comparison of serum aldosterone at the end of the confirmatory tests. This graph compares the end-test serum aldosterone (open circle) in Groups A (A) and B (B). Passing–Bablok regression analysis was used to analyze the differences between the compared confirmatory tests. In both study groups, wide 95% confidence intervals (CI) describing the regression line indicate only moderate agreement in the main results of the compared confirmatory tests. Bold lines indicate regression lines; grey lines indicate 95% CI; and dotted lines indicate identity lines.