The serum aldosterone–renin quotient (ARQ; aldosterone-renin ratio, ARR) is considered a very reliable screening parameter in the diagnosis of Conn syndrome. Conn syndrome is a form of primary hyperaldosteronism. It is characterized by an overproduction of aldosterone in the adrenal cortex due to an adenoma (benign tumor). Aldosterone is a mineralocorticoid that regulates fluid and electrolyte (blood salt) balance with other hormones such as renin and angiotensin. Screening with the aldosterone-renin quotient should be performed in the following patients:
- Arterial hypertension (high blood pressure).
- Blood pressure values > 150/100 mmHg in three measurements on three days.
- Blood pressure values > 140/90 mmHg under three antihypertensive drugs.
- > Grade 2 (> 160/100 mmHg)
- Hypokalemic hypertension (arterial hypertension combined with hypokalemia (potassium deficiency).
- Arterial hypertension in combination with adrenal incidentaloma – individuals with hypertension diagnosed with adrenal neoplasm.
- First-degree relatives of individuals with primary hyperaldosteronism.
- Arterial hypertension combined with positive family history of early hypertension manifestation or apoplexy (stroke) before 40 years of age
The procedure
Material needed
- Blood serum and EDTA plasma (frozen) – serum aldosterone and renin concentration (renin activity, if applicable); analyze material on the same day.
Preparation of the patient
The following medications should be discontinued before the examination:
- Antihypertensives (antihypertensives) – beta blockers* * , central alpha-2 agonists, ACE inhibitors* , angiotensin II receptor blockers* , calcium antagonists (discontinue 2 weeks prior).
- Diuretics (dehydrating drugs) – loop diuretics (eg, furosemide, torasemide, bumetanide, piretanide, acetanide) – discontinue 1 week before.
- Non-steroidal anti-inflammatory drugs (NSAIDs, pain relievers; discontinue 2 weeks prior).
- Renin inhibitors
- Potassium-sparing diuretics: Triamterene, spironolactone, amiloride; eplerenone (aldosterone antagonist) – as early as four weeks prior to testing.
* Increase renin concentration (→ false negative findings) * * Decrease renin and aldosterone concentration (→ false positive findings).
Factors that may influence values:
- Advanced age – individuals > 65 years of age have decreased renin levels.
- Patient positioning during blood collection – blood collection in sitting position after previous rest (circa 10 min).
- Malignant hypertension – severe course of hypertension.
- Renovascular hypertension – high blood pressure due to renal artery stenosis (renal artery stenosis).
- Disturbances in potassium balance – compensate for potassium deficiency from one week before the examination.
- Disorders in sodium balance – discontinue low-salt diet one week before, i.e., no salt restriction!
- Disturbances in the kidney function
- Pregnancy
- Time of day – blood collection between 9 and 10 a.m.; patient should sit for 5 to 15 minutes beforehand
- Different methods for the determination of renin in different laboratories.
Standard values (from different providers)*
| Threshold value in [ng/l aldosterone]/[ng/l renin]. | 50 |
| Aldosterone (pg/ml)/ Renin (pg/ml) | < 20 |
* Test values depend on the different test systems and need careful laboratory validation.
Indications
- Suspicion of Conn syndrome
Interpretation
Interpretation of increased values
- Conn syndrome (primary hyperaldosteronism).
Interpretation of decreased values
- Not relevant
Additional Notes * Since discontinuation of the above antihypertensives (blood pressure-lowering medications) may result in severely elevated blood pressure levels with increased symptomatology, the following antihypertensives may be used:
- Doxazosin
- Hydralazine
- Prazosin
- Terazosin
- Verapamil
Confirmatory testing may not be necessary in patients with spontaneous hypokalemia, suppressed renin, and plasma aldosterone concentration > 20 ng/dl.A saline loading test, fludrocortisone suppression test, or captopril loading test can be performed as a confirmatory test when the serum aldosterone-renin quotient is positive.