Lab Test

Erythrocyte Porphyrins, Free

Free Erythrocyte Porphyrins (FEP), Whole Blood, Erythrocyte Porphyrin (EP), Whole Blood , RBC Porphyrins, Free, ARUP #20610, EPIC: LAB6612, SOFT: XFEP

Test Codes

ARUP #20610, EPIC: LAB6612, SOFT: XFEP


The specimen should be tested for Lead FIRST to avoid potential contamination problems.

Specimen Collection Criteria

Collect (preferred specimen): One Royal Blue-top EDTA tube.
Also acceptable: One Lavender-top EDTA tube. If the specimen is also being tested for Lead, a Royal Blue-top EDTA must be used.

  • Protect specimen from light.
  • Refrigerate the specimen immediately after collection.

Physician Office/Draw Specimen Preparation

Protect specimen from light. Do not centrifuge. Refrigerate (2-8°C or 36-46°F) specimen immediately after collection and maintain refrigerated prior to transport.

Preparation for Courier Transport

Transport: 1.0 mL whole blood, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Rejection Criteria

  • Clotted specimens.
  • Specimens not collected in EDTA.
  • Specimens not protected from light.
  • Specimens not collected and processed as indicated.

In-Lab Processing

Protect specimen from light. Do not centrifuge. Refrigerate (2-8°C or 36-46°F) specimen immediately after collection and maintain refrigerated prior to transport.

Transport: 1.0 mL whole blood, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL) 


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 14 days
Frozen (-20°C/-4°F or below): 30 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Sendout Laboratory with any questions.


Sent to ARUP Laboratories, Salt Lake City, UT.


Monday, Wednesday, Saturday.
Results available in 2-5 days.

Reference Range

0-35 mcg/dL.

Test Methodology



  • Elevated FEP results are seen in early and late iron deficiency, in the anemia of chronic disease, and in chronic lead poisoning (typically when blood lead is greater than 25 mcg/dL). Elevated protoporphyrin (as in erythropoietin protoporphyria) and zinc coproporphyrin (usually associated with delivery) can also increase the apparent FEP signal. Specimens which are hemolyzed, clotted, or improperly aliquoted can also show false elevations.
  • Whole blood zinc protoporphyrin gives similar results to the FEP test, is less expensive and has a faster turnaround time. A more specific test for free protoporphyrin is total serum porphyrins.

Clinical Utility

This assay aids in the diagnosis of iron deficiency, anemia associated with chronic disease, and lead exposure. Increased blood porphyrins levels are associated with erythropoietic protoporphyria (a rare genetic condition associated with photosensitivity).

CPT Codes



Last Updated


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This directory currently reflects information only for specimens collected and/or processed at the
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