Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1123 page)

   Standing: 0.7–3.3 ng/mL/hour

   Normal values depend on the laboratory and the patients prevailing Na and K, status of hydration, and posture. Only stimulated values are of practical value in evaluating hypertensive patients.

   Use

   Particularly useful to diagnose curable hypertension (e.g., primary aldosteronism, unilateral renal artery stenosis).

   May help differentiate patients with volume excess (e.g., primary aldosteronism) with low PRA from those with medium to high PRA; if latter group shows marked increase in PRA during captopril test, patients should be worked up for renovascular hypertension, but those with little or no increase are not likely to have curable renovascular hypertension.

   Captopril test criteria for renovascular hypertension: stimulated PRA ≥12 μg/L/hour, absolute increase PRA ≥10 μg/L/hour, increase PRA ≥150% (or ≥400% if baseline PRA <3 μg/L/hour).

   In children with salt-losing form of congenital adrenal hyperplasia due to 21-hydroxylase deficiency, severity of disease is related to degree of increase. PRA level may serve as guide to adequate mineralocorticoid replacement therapy.

   Interpretation

Increased In

   Secondary aldosteronism (usually very high levels), especially malignant or severe hypertension 50–80% of patients with renovascular hypertension (Table 16.66).

   Normal or high PRA is of limited value to diagnose or rule out renal vascular hypertension.

   Very high PRA is highly predictive but has poor sensitivity.

   Low PRA using renin–sodium nomogram in untreated patients with normal serum creatinine is strongly against this diagnosis.

   Fifteen percent of patients with essential hypertension (high-renin hypertension)