[Biochemical detection of Conn's adenoma: definition of criteria and reference values]

Primary hyperaldosteronism is a diagnosis which should be considered in refractory hypertension even in the absence of any hypokalaemia. Its detection relies above all on the levels of renin and aldosterone. The aldosterone/renin ratio has been proposed as the most sensitive criterium. The reference values used for the diagnosis of primary hyperaldosteronism are very variable in the literature, depending not only on the method used but also on the criteria used for their determination. In this study we evaluated the defined reference values prospectively by studying a population of patients with a Conn's adenoma treated surgically. The study included an initial retrospective period which allowed identification of 29 cases of Conn's adenoma treated surgically, and a 9 month prospective period during which 212 reports were collected. During this prospective period a further 9 cases of Conn's adenoma were detected, which were successfully treated with surgery. Analysis to discriminate the 38 Conn's adenomata from the rest showed that 3 parameters contributed significantly and independently to the diagnosis: supine plasma renin activity (ARPc), supine aldosteronaemia and the erect aldosterone/renin ratio, allowing correct classification in 88% of the cases. The reference ranges of these 3 parameters were calculated in order to give a sensitivity of 100% and the best possible specificity, therefore allowing a combined criterium involving all 3 parameters to be defined: ARPc < 0.45 ng/ml/h, supine aldosteronaemia >417 pmol/l, and erect aldosterone/renin >1180.