Reproducibility of plasma renin activity (PRA) profile in essential hypertension patients

Whether the same patient with essential hypertension (EH) has the same PRA profile at different occasions, is still uncertain. The validity of the classification of these patients into low or normal renin hypertension depends upon the reproducibility of this profile. A nomogram based on PRA and 24 hr urine sodium in normals, was constructed by computing the regression line with its tolerance limits of not less than 95%. In 30 patients with EH, the PRA and 24 hr urine sodium were determined in 2 separate occasions. Classification of patients showed a change of 30% when PRA was taken during at least 2 hours recumbency. However, when PRA following ambulation is considered, the change appeared only in 6/30 (20%). This change was not large. Thus good reproducibility of PRA is obtained on post-ambulation PRA and changes larger than the 95% tolerance limits, are considered.