Table 2. Factors that may lead to false-positive or false-negative aldosterone:renin ratio results.
| Factor | Effect on aldosterone plasma concentration | Effect on renin concentration | Effect on aldosterone:renin ratio |
|---|---|---|---|
| Drugs* | |||
| Beta adrenergic blockers | ↓ | ↓ ↓ | ↑ (FP) |
| Central agonists (e.g. clonidine, alpha methyldopa) | ↓ | ↓ ↓ | ↑ (FP) |
| Non-steroidal anti-inflammatory drugs | ↓ | ↓ ↓ | ↑ (FP) |
| Potassium wasting diuretics | → ↓ | ↑ ↑ | ↓ (FN) |
| Potassium sparing diuretics | ↑ | ↑ ↑ | ↓ (FN) |
| ACE inhibitors | ↓ | ↑ ↑ | ↓ (FN) |
| Angiotensin receptor antagonist | ↓ | ↑ ↑ | ↓ (FN) |
| Calcium channel blockers (dihydropyridines) | → ↓ | ↑ | ↓ (FN) |
| Renin inhibitors | ↓ | ↓ ↑ | ↑ (FP) |
| ↓ (FN) | |||
| Potassium status | |||
| Hypokalaemia | ↓ | → ↑ | ↓ (FN) |
| Potassium loading | ↑ | → ↓ | ↑ |
| Dietary sodium | |||
| Sodium restriction | ↑ | ↑ ↑ | ↑ (FN) |
| Sodium loading | ↓ | ↓ ↓ | ↑ (FP) |
| Advancing age | ↓ | ↓ ↓ | ↑ (FP) |
| Premenopausal women (vs males) † | → ↑ | ↓ | ↑ (FP) |
| Other conditions | |||
| Renal impairment | → | ↓ | ↑ (FP) |
| PHA-2 | → | ↓ | ↑ (FP) |
| Pregnancy | ↑ | ↑ ↑ | ↓ (FN) |
| Renovascular hypertension | ↑ | ↑ ↑ | ↓ (FN) |
| Malignant hypertension | ↑ | ↑ ↑ | ↓ (FN) |
FN false negative, FP false positive
↓ decreases effect, ↑ increases effect → has no effect
PHA-2 pseudohypoaldosteronism type 2 (familial hypertension and hyperkalaemia with normal glomerular filtration rate)
* Renin inhibitors lower plasma renin activity, but raise direct renin concentration. This would be expected to result in false-positive aldosterone:renin ratios for renin measured as plasma renin activity and false negatives for renin measured as direct renin concentration.
† In premenopausal, ovulating women, plasma aldosterone concentrations measured during the menses or the proliferative phase of the menstrual cycle are similar to those of men but rise briskly in the luteal phase. Because renin concentrations are lower, the aldosterone:renin ratio is higher than in men for all phases of the cycle, but especially during the luteal phase during which aldosterone rises to a greater extent than renin. False positives can occur during the luteal phase, but only if renin is measured as direct renin concentration and not plasma renin activity. In preliminary studies, some investigations have found false positives on the current cut-offs for women in the luteal phase. Accordingly, it would seem sensible to screen women at risk in the follicular phase, if practicable.
Source: adapted from reference 3