Renin and Aldosterone:Renin ratio (ARR)
- Aldosterone:renin ratio is useful in the investigation of hypertension, especially if a patient has resistant hypertension, is persistently hypokalaemic (but note that 50% patients with aldosterone producing adenomas are reportedly normokalaemic), or if no obvious cause is found for the hypertension in a younger patient.
- The renin-aldosterone axis is primarily regulated by renal blood flow. Patients under investigation should therefore not be taking any drugs that interfere with fluid balance or potassium.
- Patients should be normally hydrated and have an adequate oral intake of sodium. Significant hypokalaemia must be avoided since this suppresses aldosterone secretion (note that the effect on increasing oral sodium will be to considerably increase urinary potassium excretion).
- Please contact the duty biochemist for details of required patient preparation prior to performing this investigation.
Plasma Renin Activiy
- Plasma Renin Activity is sometimes assayed on its own, for example in a patient with known congenital adrenal hyperplasia or Addison's who is being monitored for adequacy of mineralocorticoid replacement.
Please note that all samples must remain at room temperature (do not chill) and be sent immediately to the laboratory.
For adults, blood taken into a 4ml EDTA Tube
For children, blood taken into a 2ml EDTA tube
For neonates, blood taken into a 1mL EDTA minicollect tube
Do not store samples for either Aldosterone:Renin Ratio and Plasma Renin Activity. Send immediately to the laboratory at room temperature (do not chill). Samples must reach the laboratory preferably within 1 hour but certainly in less than 2 hours.
Please telephone the laboratory to alert before collecting so that samples can be dealt with immediately.
For both Aldosterone:Renin Ratio and Plasma Renin Activity, please include relevant clinical details, including current anti-hypertensive medication. If current medication is not provided, analysis may be delayed as this is required before samples can be sent for analysis.
Samples for Plasma Renin Activity are sent once a week by courier for analysis at Charing Cross, with results expected back within 5 weeks.
Samples for Aldosterone:Renin Ratio are sent once a week by courier for analysis at Kings College Hospital London, with results expected back within 2 weeks.
Conn's unlikely: Aldosterone:Renin Ratio less than 80
Conn's not excluded: Aldosterone:Renin Ratio greater than 80 to 200
Conn's likely: Aldosterone:Renin Ratio greater than 200
To learn more about aldosterone and renin visit Lab Tests Online
Page last updated: 20/04/2021