The diagnosis of primary aldosteronism typically requires at least one confirmatory test. The fludrocortisone suppression test is generally accepted as a reliable confirmatory test, but it is cumbersome. Evidence from accuracy studies of the saline infusion test (SIT) and the captopril challenge test (CCT) has provided conflicting results. This prospective study aimed to evaluate the diagnostic accuracy of the SIT and CCT using fludrocortisone suppression test as the reference standard. One hundred thirty-five patients diagnosed with primary aldosteronism and 101 patients diagnosed with essential hypertension who completed the 3 confirmatory tests were included for the diagnostic accuracy analysis. The areas under the receiver-operator characteristics curves of the CCT and SIT were 0.96 (95% confidence interval [CI], 0.92-0.98) and 0.96 (95% CI, 0.92-0.98), respectively, using post-test plasma aldosterone concentration (PAC) for diagnosis. However, the areas under the receiver-operator characteristics curves of the CCT decreased to 0.71 (95% CI, 0.65-0.77) when the PAC suppression percentage was used to diagnose primary aldosteronism. The optimal cutoff of PAC post-CCT was set at 11 ng/dL, resulting in a sensitivity of 0.90 (95% CI, 0.84-0.95) and a specificity of 0.90 (95% CI, 0.83-0.95), which were not significantly different from those of SIT (with PAC post-SIT set at 8 ng/dL, sensitivity: 0.85 [95% CI, 0.78-0.91], =0.192; specificity: 0.92 [95% CI, 0.85-0.97],=0.551). In conclusion, both CCT and SIT are accurate alternatives to the more complex fludrocortisone suppression test. Because CCT is safe and much easier to perform, it may serve as a more feasible alternative. When interpreting the results of CCT, PAC post-CCT is highly recommended.
Aim This retrospective study is aimed at investigating whether aldosterone-renin ratio (ARR) cutoffs calculated by the plasma aldosterone concentration (PAC)/plasma renin concentration (PRC) should be set differently in patients of different ages. Methods 521 hypertensive patients were screened for primary aldosteronism (PA) by the PAC/PRC. 174 patients diagnosed with PA and 311 patients with essential hypertension (EH) were included in the final analysis. Subjects were subdivided into four age groups: <40, 40–49, 50–59, and ≥60 years old. Results The accuracy of the ARR varied greatly among the different age groups. An ARR of 3.7 (ng/dl)/(μIU/ml) had a sensitivity of 100% and a specificity of 80% in patients ≥ 60 years old. With this cutoff, the sensitivities in patients < 40, 40–49, and 50–59 years old were 74%, 82%, and 87%, respectively, and the specificities were 94%, 95%, and 94%, respectively. To achieve a sensitivity higher than 90%, the ARR cutoff needed to be lowered to 2.0 (ng/dl)/(μIU/ml) for patients 40–49 and 50–59 years old, resulting in sensitivities of 90% and 95%, respectively, and specificities of 80% and 84%, respectively. To achieve a sensitivity higher than 90%, the ARR cutoff needed to be lowered to 1.0 (ng/dl)/(μIU/ml) for patients < 40 years old, resulting in a sensitivity of 90% and a specificity of 82%. Conclusions An ARR of 3.7 (ng/dl)/(μIU/ml) is optimal for patients ≥ 60 years; for patients 40–59 years, the optimal ARR cutoff is 2.0; for those younger than 40 years, an ARR of 1.0 may be more reasonable.
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