Plasma aldosterone to renin ratio predicts treatment response in primary aldosteronism: is volume loading needed?

Volume loading is considered the golden standard of the confirmatory tests in the diagnostics of primary aldosteronism (PA). However, it is time-consuming, and it is unclear to what extent it improves the diagnostics of PA in comparison to simple screening tests. To study this question, the diagnostics with and without oral sodium loading (OSL) were evaluated by receiver operating characteristic curves analyses in 77 consecutive OSL patients. The final diagnosis was essential hypertension in 39 cases and PA in 38 cases, determined by review of the patient records, biochemical tests, imaging findings, and the response to therapy with spironolactone and/or operation. Plasma aldosterone-to-renin-activity ratio (ARR) and daily urinary aldosterone had a good diagnostic ability that did not significantly improve by accomplishing OSL. Cut-off values with optimal sensitivity and specificity were >or=1050 pmol/l per ng/ml/h for upright ARR, and >or=45 nmol/day for daily urinary aldosterone. To conclude, carefully conducted outpatient tests are sufficient for the diagnostics of PA, when the diagnosis is justified by the positive response to treatment. However, volume loading serves as an additional diagnostic tool in the most problematic cases, improving slightly the discriminative ability of urinary aldosterone determination.