ABSTRACT
Measurement of the integrated concentration is most suited for the study of blood components that fluctuate rapidly. The integrated concentration of plasma aldosterone (IC-ALDO) and plasma renin activity (IC-PRA) were measured in 24 patients with essential hypertension and in 10 normal adult subjects, using a non-thrombogenic 24-hour constant blood withdrawal system. The integrated concentration of plasma aldosterone in the control subjects was 7.7 +/- 1.8 ng/100 ml (mean +/- 1 SD). Eight hypertensive patients had IC-ALDOs that were more than 3 standard deviations above the mean. Although the mean IC-PRA of the hypertensive patients was lower than the mean of controls (0.6 +/- 0.6 and 0.9 +/- 0.6, respectively), the difference was not significant. However, high integrated concentration of plasma aldosterone was mostly associated with low integrated concentration of plasma renin activity. Consequently, the ratio of IC-ALDO to IC-PRA in the hypertensive patients was significantly higher (p less than 0.001). In six hypertensive patients the ratio was more than 4 standard deviations above the mean for the normal control subjects (12.2 +/- 7.6). Individuals with inappropriately high integrated concentrations of plasma aldosterone can therefore be identified by the simultaneous determination of IC-ALDO and IC-PRA.
