PRIMARY ALDOSTERONISM - DIAGNOSTIC AND PR OGNOSTIC VALUE OF POTASSIUM, RENIN, ALDOSTERONE AND THE ALDOSTERONE RENIN RATIO/

Objectives: To evaluate diagnostic criteria in primary aldosteronism, we studied the sensitivity and specificity of potassium, renin, aldost erone and the renin/aldosterone ratio in 60 patients undergoing surger y for Conn's adenoma, 50 patients with primary hypertension and 49 nor mal controls. We also searched for a relationship between these parame ters and the blood pressure outcome of surgery. Methods: The diagnosti c value of the tests was quantified using the Youden index after adjus tment for receiver operating characteristic (ROC) thresholds. Results: Potassium level in patients was lower than in controls, but in 22%, k aliaemia was greater than or equal to 3.5 mmol/l and the threshold giv ing the best Youden index (0.93) was 3.9 mmol/l. The diagnostic power of active renin was low (Youden index 0,28), but the Youden indexes fo r aldosterone level and the aldosterone/renin ratio in supine position were 0.68 and 0.66 respectively. After a mean follow-up of 8.7 months after surgery, 70% of the patients had normal or improved blood press ure levels. None of the biological parameters evaluated was associated with blood pressure outcome, but age > 55 years was related to unfavo rable outcome (sensitivity and specificity 80 and 60%). Conclusion: Th e threshold level requiring a search for an adenoma should be raised. When the potassium level is less than or equal to 3.9 mmol/l the aldos terone/renin ratio should be measured in supine position since it eval uates the dissociation between renin and aldosterone seen in primary h yperaldosteronism. The effect of age on the surgical result emphasizes the importance of early diagnosis.