Renin, Direct
Also known as: RENIND
Use
The Renin, Direct test measures the concentration of direct renin in the blood, an enzyme involved in blood pressure regulation and electrolyte balance. The test is commonly used to evaluate hypertension and diagnose primary aldosteronism. It is often performed alongside aldosterone measurements to compute the aldosterone-renin ratio, aiding in the differentiation of primary aldosteronism from other causes of hypertension. Understanding the direct renin level is crucial in assessing the renin-angiotensin system's function, particularly when patients present with symptoms such as uncontrolled or resistant hypertension.
Special Instructions
Do not use this test for patients treated with Cathepsin B. Menstruating females and those taking estrogen-containing medications may have lower renin direct concentrations, resulting in falsely high aldosterone-renin ratios. It is advisable to follow the Endocrine Society's recommendations for patient preparation and specimen collection to minimize errors and ensure accurate readings of the aldosterone-renin ratio.
Limitations
This test should not be used if the patient is currently receiving treatment with Cathepsin B, as it can interfere with test results. Additionally, factors such as posture, time of day, and medication use, particularly estrogen-containing medications, can affect test accuracy. Fasting is recommended to reduce variability, though not strictly required. Specimen collection conditions, including the use of refrigerated tubes or icing of samples, can lead to sample rejection.
FDA ApprovedNew York Approved
Methodology
Immunoassay (CLIA)
Biomarkers
LOINC Codes
- 35570-1
Result Turnaround Time
1-5 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
2 mL
Minimum Volume
1 mL
Container
Lavender (EDTA) tube; ARUP Standard Transport Tube after centrifugation
Collection Instructions
Collect midmorning between 7am to 10am after patient has been sitting, standing, or walking for at least 30 minutes and seated for 5-15 minutes. Process blood at room temperature and centrifuge in a non-refrigerated centrifuge. Separate plasma from cells ASAP or within 2 hours of collection and freeze immediately.
Patient Preparation
If patient is supine, they should be in this position for at least 30 minutes prior to collection. Fasting specimens are recommended but not required.
Storage Instructions
Frozen
Causes for Rejection
Serum; Specimens collected in citrate, heparin, or oxalate; Grossly hemolyzed or refrigerated specimens
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 8 hours |
| Refrigerated | Unacceptable |
| Frozen | 4 weeks |