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Sodium restriction increases risk for false negatives in primary aldosteronism screening
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A low-sodium diet can result in false interpretation of primary aldosteronism screening, with milder phenotypes of the disorder most vulnerable to misinterpretation during the screening process, according to recent study data.
“Sodium restriction is recommended in hypertension; however, it can significantly raise plasma renin activity, normalize the aldosterone-to-renin ratio, and result in false interpretation of primary aldosteronism screening,” Rene Baudrand, MD, of the department of endocrinology, School of Medicine, Pontifica Universidad Catolica De Chile, and colleagues wrote. “Optimal screening for primary aldosteronism should occur under conditions of high dietary sodium intake.”
The most common method in screening for primary aldosteronism is the aldosterone-to-renin ratio. Researchers compared the screening results of untreated patients with hypertension with an aldosterone-to-renin ratio greater than 20 after two different dietary interventions (n = 241). Participants were first screened after 1 week of a high-sodium diet and again after 1 week on a low-sodium diet.
Although 79 of the 241 participants (33%) screened positive for primary aldosteronism on the high-sodium diet, 44 of those 79 (56%) screened negative for the disorder on a low-sodium diet. Those participants who tested negative on a low-sodium diet but positive on a high-sodium diet had significantly higher plasma renin activity than participants who screened positive on both diets, the researchers reported.
Baudrand and colleagues wrote that they found an inverse relationship between plasma renin activity and 24-hour urinary sodium balance on the low-sodium diet (r = –0.263, P < .001). White patients were more susceptible to a false negative than other racial/ethnic groups, the researchers wrote, because discordant screening was associated with a higher prevalence of white race (90% vs. 62%; P = .002), even among participants with comparable ages, sex and BMI.
“Since primary aldosteronism is usually diagnosed from the hypertensive population that is routinely advised to restrict dietary sodium intake, these results indicate that a substantial portion of individuals with milder forms of primary aldosteronism may be at risk of being misdiagnosed or underdiagnosed,” Baudrand and colleagues wrote. “We emphasize and extend The Endocrine Society recommendation that using the aldosterone-to-renin ratio to screen for primary aldosteronism should optimally occur after prescribing a high dietary sodium intake, and ideally with some confirmation that this has occurred.” – by Andy Polhamus
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