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31891M
PROTOPORPHYRINS, FRACTIONATION, RBC (WASHED ERYTHROCYTES

Test Code 31891M 
Test PROTOPORPHYRINS, FRACTIONATION, RBC (WASHED ERYTHROCYTES 
Methodology High-Performance Liquid Chromatography (HPLC) with
Fluorescence Detection 
Description Includes separate quantitation of zinc
protoporphyrins and free protoporphyrins.

See "Porphyria (Acute) Testing Algorithm" and "Porphyria (Cutaneous) Testing Algorithm" in Special Instructions.

Useful for:
Establishing a biochemical diagnosis of erythropoietic protoporphyria.

Differential diagnosis of chronic intoxication from exposure to a variety of causes including heavy metals and chemicals.

Differential diagnosis in some cases of iron-deficiency anemia.

There are 2 test options: whole blood (#8739 "Protoporphyrins, Fractionation, Whole Blood") and washed RBCs (#31891 "Protoporphyrins, Fractionation, Washed Erythrocytes"). The whole blood option is easiest for clients but requires that the specimen arrive at Mayo Medical Laboratories within 48 hours of draw. When this cannot be ensured, washed RBCs should be submitted. 

Specimen Submit a full, green-top (heparin) tube of washed erythrocyte suspension (minimum volume, 1 mL of washed and resuspended erythrocytes).

Collection Instructions:
1. Patient should abstain from alcohol for 24 hours.
Note: Include a list of medications the patient is currently taking and forward with the specimen.
2. Process entire specimen as follows:
A. Immediately place specimen on wet ice.
B. Transfer up to 5 mL of specimen to a 12-mL graduated centrifuge tube.
C. Centrifuge specimen for 10 minutes at 2,000 rpm.
D. Record volume of packed cells and the total volume of the specimen. This information must be sent with the specimen.
E. Discard supernatant plasma.
F. Wash packed erythrocytes 2 times by resuspension of at least an equal amount of cold 0.9% saline, mix, and centrifuge for 5 minutes at 2,000 rpm, discarding supernatant after each washing.
G. Resuspend packed cells to the original total volume with 0.9% saline. Invert specimen gently to mix.
H. Send specimen in plastic vial.
Note: Volume of packed cells and total volume of erythrocyte suspension (red cells + saline) are required. 

Reference Values FREE PROTOPORPHYRIN
<20 g/dL packed cells

ZINC-COMPLEXED PROTOPORPHYRIN
<60 g/dL packed cells

See "The Heme Biosynthetic Pathway" in Special Instructions. 

Analytic Time 2 Days (not reported on Saturday or Sunday) 
Day(s) Test Set Up Monday through Friday 
CPT Code(s) 84202