Screening for primary aldosteronism: Implications of an increased plasma aldosterone/renin ratio

Background: The value of the ratio of plasma aldosterone concentration (aldosterone) to plasma renin activity (renin) to identify patients at risk for primary aldosteronism is controversial. We determined the sensitivity, specificity, and predictive value of the ratio to identify combinations of renin and aldosterone compatible with primary aldosteronism. Methods: The ratio was calculated in 505 adults with essential hypertension (143 black women, 82 black men, 122 white women, and 158 white men). We used a conventional cutpoint for an increased ratio (i.e., 20 mL/dL . h) The primary combination of renin and aldosterone considered compatible with primary aldosteronism was increased aldosterone for the concomitant renin, defined as aldosterone in the highest quartile predicted by linear regression on renin. Renin was considered low if it was in the lowest quartile of the sample distribution. Results: The sensitivity of the ratio to identify individuals with increased aldosterone for the concomitant renin was 66% (80% in blacks and 56% in whites; P = 0.009), and the specificity of the ratio was 67% (46% in blacks and 84% in whites; P <0.0001). In 36% of instances of an increased ratio, it was a measure of low renin alone without increased aldosterone for renin (32% in blacks and 45% in whites; P = 0.072). The positive predictive value of the ratio to identify individuals with increased aldosterone for the concomitant renin was 34% (49% in whites and 27% in blacks; P <0.002). Conclusion: The aldosterone/renin ratio lacks sensitivity and specificity and has only a modest predictive value for combinations of renin and aldosterone that are compatible with primary aldosteronism. (C) 2002 American Association for Clinical Chemistry.