Renin Assay
Test OverviewA renin assay blood test is done to find the
cause of
high blood pressure (hypertension). Renin is an
enzyme made by special cells in the
kidneys. Renin works with aldosterone (a
hormone made by the
adrenal glands) and several other substances to help
balance sodium and
potassium levels in the blood and fluid levels in the
body, which affects your blood pressure. A renin test is often
done at the same time as an aldosterone test. In some people, it may be normal
to have high blood levels of both renin and aldosterone. If renin levels are
low and aldosterone levels are high, a tumor may be present in the
adrenal glands. Why It Is DoneA renin test is done to find the cause
of high blood pressure (hypertension), especially when potassium levels in the
blood are low. How To Prepare For 2 to 4 weeks before the test, you
may be asked to stop taking medicines that can affect the test, such as
diuretics,
estrogens, and high blood pressure medicines
(especially
beta-blockers and ACE inhibitors). Your doctor may have you take other medicines for a few weeks that will not
change the renin test results. Do not eat natural black licorice
for 2 weeks before the test. Do not eat or drink foods that contain caffeine
the day before the test. Natural licorice and caffeine can change the test
results. For 3 days before a renin test, you may be asked to
follow a special low-sodium diet. You may be asked to not eat or
drink anything for 8 hours before the test. How It Is DoneYou may need to sit or lie down to
relax for 1 to 2 hours before your blood is collected. A second blood sample
may be collected after you move around for 2 hours. The health
professional drawing blood will: - Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with
alcohol.
- Put the needle into the vein. More than one needle stick
may be needed.
- Attach a tube to the needle to fill it with
blood.
- Remove the band from your arm when enough blood is
collected.
- Put a gauze pad or cotton ball over the needle site as
the needle is removed.
- Put pressure on the site and then put on a
bandage.
How It FeelsThe blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch. RisksThere is very little chance of a problem from
having a blood sample taken from a vein. - You may get a small bruise at the site. You
can lower the chance of bruising by keeping pressure on the site for several
minutes.
- In rare cases, the vein may become swollen after the
blood sample is taken. This problem is called phlebitis. A warm compress can be
used several times a day to treat this.
ResultsA renin assay blood test is done to find
the cause of
high blood pressure (hypertension). The time of day
and your position (standing, sitting, or lying down) before the blood sample is
collected, your age, and the level of sodium in your blood all affect the test
results. NormalThe normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab. Plasma renin activityfootnote 1| Adult (upright
position, normal-sodium diet) | 0.7-3.3
nanograms per milliliter per hour (ng/mL/hr) or
0.7-3.3
micrograms per liter per hour (mcg/L/hr) |
|---|
| Adult (lying down, normal-sodium diet) | 0.2-1.6 ng/mL/hr or 0.2-1.6
mcg/L/hr |
|---|
| Adult (upright position,
low-sodium diet) | 4.2-19.8 ng/mL/hr or 4.2-19.8
mcg/L/hr |
|---|
| Adult (lying down, low-sodium diet) | 0.4-3.2 ng/mL/hr or 0.4-3.2
mcg/L/hr |
|---|
Many things can affect renin test results. Your
doctor will talk with you about any abnormal results that may be related to
your symptoms and past health. High values A high renin value can mean kidney
disease, blockage of an artery leading to a kidney,
Addison's disease,
cirrhosis, excessive bleeding (hemorrhage), or
malignant high blood pressure is present. Low valuesA low renin value can mean
some types of kidney disease or Conn's syndrome is present. What Affects the TestReasons you may not be able to
have the test or why the results may not be helpful include: - Eating natural black licorice in the 2 weeks
before the test.
- Taking some medicines used to treat high blood
pressure.
- Taking aspirin, caffeine,
estrogens, or
diuretics.
- Your position (standing,
sitting, or lying down) before the test is done or the time of day when the
blood sample is drawn, as well as recent salt intake.
- Taking very
high doses of
corticosteroids.
- Being pregnant.
What To Think About- A renin test is often done at the same time as
an aldosterone test. To learn more, see the topic
Aldosterone.
- A renin stimulation test may
occasionally be done if blood renin levels are low. To prepare for this test,
you will eat a low-sodium diet for 3 days. A blood renin level will be drawn
and a diuretic, usually furosemide (Lasix), will be put in a vein (intravenous)
in your arm. Normally, blood renin levels will increase, but in Conn's syndrome
blood renin levels will not change after taking the diuretic.
- Many
hospitals now measure renin activity with the renin direct immunoassay, which
measures the amount of renin in the blood. A plasma renin activity (PRA) test
measures the production of a hormone called angiotensin I rather than renin itself. A renin
direct immunoassay is easier to do and can generally be done instead of the PRA
test. But in some situations (such as pregnancy), PRA results may be more
accurate than the renin direct immunoassay.
- Other tests
that may be done to investigate high blood pressure include
duplex Doppler ultrasound,
arteriography, magnetic resonance imaging (MRI), and magnetic resonance angiography (MRA).
ReferencesCitations- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Other Works Consulted- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
CreditsByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerAlan C. Dalkin, MD - Endocrinology Current as of:
May 3, 2017 Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins. Last modified on: 8 September 2017
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