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Test Code FENA or LAB2650 Fractional Excretion of Sodium (FENA)

Important Note

This orderable requires a urine and serum specimen.

Specimen Requirements

Container Type:

       1. Urine Specimen

Sterile urine cup

 

       2. Blood Specimen

Optimal: Gold or Mint

Acceptable: Red or Green

 
Optimal Collection Volume: 
  • Urine: 10 mL
  • Blood: 5 mL or full tube
Minimum Volume:
  • Urine: 2 mL
  • Blood: 1 mL
Collection Instructions:

       Urine

  1. Collect a random urine sample from the patient.
  2. Ensure the lid is secured tightly before sending it to the lab.
  3. Ensure that no preservatives are used.

       Blood

  1. Gently invert the sample 5-6 times after collection.
Specimen Transport:

Refrigerate
Processing Instructions: 
  1. If serum, allow the specimen to clot for 30 minutes.
  2. For urine specimens, pour off sample into aliquot and centrifuge.
  3. Centrifuge specimen within 2 hours of collection.
  4. After centrifugation, specimen tubes without a gel barrier should have the serum or plasma aliquoted to a false bottom container
  5. Keep the serum or plasma refrigerated until testing can be performed.

Specimen Stability

Specimen Type Temperature Time
Urine Refrigerated 7 days
Room Temperature 2 days

 

Specimen Type Temperature Time
Blood Refrigerated 7 days
Room Temperature 7 days

Specimen Rejection Criteria

Hemolysis Mild OK; Moderate OK; Gross Reject
Lipemia Mild OK; Moderate OK; Gross Reject
Icterus Mild OK; Moderate OK; Gross Reject
Other Quantity not sufficient

Useful For

Fractional excretion of sodium (FENA) is the fraction of sodium excreted by the body relative to the amount filtered by the kidney.

Methodology

Roche Cobas

  • Sodium - Potentiometric, Ion-selective electrode, indirect
  • Creatinine - Enzymatic colorimetric

Reference Ranges

Low FENA (<1)

High FENA (>2)

Associated Disease States

Prerenal Azotemia

Acute Tubular Necrosis

Acut Glom. Nephritis

Urinary Obstruction

Hepatorenal Syndrome

Chronic Uremia, Duretics

Day(s) Performed

24/7

Expected TAT

Same day

Performing Laboratory

Bronson Laboratory, Chemistry - Kalamazoo, Battle Creek, Paw Paw, South Haven

Sample Retention Time

7 days

CPT Code

  • Urine Sodium - 84300
  • Urine Creatinine - 82570
  • Blood Sodium - 84295
  • Blood Creatinine - 82565

LOINC Code

  • Urine Sodium - 2955-3
  • Urine Creatinine: 2161-8
  • Blood Sodium - 2951-2
  • Blood Creatinine: 45066-8