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Test ID: PEWE Porphyrins Evaluation, Washed Erythrocytes

Reporting Name

Porphyrin Evaluation, RBC

Useful For

Preferred test for analysis of erythrocyte porphyrins

 

Establishing a biochemical diagnosis of erythropoietic protoporphyria, and X-linked dominant protoporphyria

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
PPFWE Protoporphyrins, Fractionation, RBC Yes, (order PPFWE) No

Testing Algorithm

This test is recommended for screening patients for possible erythropoietic protoporphyria and X-linked dominant protoporphyria. In addition, it can be used for evaluation of iron-deficiency anemia and chronic lead intoxication. Testing begins with total erythrocyte porphyrins. If the result is <80 mcg/dL, it is normal and testing is complete.

 

If the total erythrocyte porphyrin value is ≥80 mcg/dL, the protoporphyrin fractionation (PPFWE) assay will automatically be performed at an additional charge. The PPFWE test results include free protoporphyrin and zinc-complexed protoporphyrin.

 

The following algorithms are available in Special Instructions:

-Porphyria (Acute) Testing Algorithm

-Porphyria (Cutaneous) Testing Algorithm

Specimen Type

Washed RBC


Specimen Required


All porphyrin tests on erythrocytes can be performed on 1 draw tube.

 

Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: Dark blue top (metal free heparin) or green top (lithium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: Washed erythrocyte suspension

Collection Instructions:

1. Patient should abstain from alcohol for 24 hours.

2. Collect and process whole blood specimen as follows:

a. Immediately place specimen on wet ice.

b. Transfer entire 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.

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. Transfer to a plastic tube and freeze.

Additional Information:

1. Volume of packed cells and total volume of erythrocyte suspension (red cells + saline) are required and must be sent with specimen.

2. Include a list of medications the patient is currently taking.

Forms: New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Washed RBC Frozen (preferred) 14 days
  Refrigerated  14 days

Reference Values

PORPHYRINS, TOTAL, RBC

<80 mcg/dL packed cells

 

FREE PROTOPORPHYRIN

<20 mcg/dL packed cells

 

ZINC-COMPLEXED PROTOPORPHYRIN

<60 mcg/dL packed cells

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

84311-Spectrophotometry, analyte not elsewhere specified

82542-Chromatography (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PEWE Porphyrin Evaluation, RBC In Process

 

Result ID Test Result Name Result LOINC Value
31942 Total Porphyrins, RBC 2814-2
31943 Interpretation 59462-2
BG569 Total cell suspension In Process
BG570 Packed cell volume In Process

Clinical Information

The porphyrias are a group of inherited disorders resulting from enzyme defects in the heme biosynthetic pathway. Depending on the specific enzyme involved, various porphyrins and their precursors accumulate in different specimen types. The patterns of porphyrin accumulation in erythrocytes and plasma and excretion of the heme precursors in urine and feces allow for the detection and differentiation of the porphyrias.

 

Testing erythrocyte porphyrin level is most informative for patients with a clinical suspicion of erythropoietic protoporphyria (EPP) or X-linked dominant protoporphyria (XLDPP). Clinical presentation of EPP and XLDPP is identical with onset of symptoms typically occurring in childhood. Cutaneous photosensitivity in sun-exposed areas of the skin generally worsens in the spring and summer months. Common symptoms may include itching, edema, erythema, stinging or burning sensations, and occasionally scarring of the skin in sun-exposed areas. Although genetic in nature, environmental factors exacerbate symptoms, significantly impacting the severity and course of disease.

 

EPP is caused by diminished ferrochelatase activity resulting in significantly increased free protoporphyrin levels in erythrocytes, plasma, and feces.

 

X-linked dominant protoporphyria is caused by gain-of-function mutations in the C-terminal end of ALAS2 gene and results in elevated erythrocyte levels of free and zinc-complexed protoporphyrin, and total protoporphyrin levels in plasma and feces.

 

Protoporphyrin fraction is the main component of erythrocyte porphyrins. When total erythrocyte porphyrins are elevated, fractionation and quantitation of zinc-complexed and free protoporphyrin are necessary to differentiate the inherited porphyrias from other causes of elevated porphyrin levels. Other possible causes of elevated erythrocyte zinc-complexed protoporphyrin may include:

-Iron-deficiency anemia, the most common cause

-Chronic intoxication by heavy metals (primarily lead) or various organic chemicals

-Congenital erythropoietic porphyria (CEP), a rare autosomal recessive porphyria caused by deficient uroporphyrinogen III synthase

-Hepatoerythropoietic porphyria (HEP), a rare autosomal recessive porphyria caused by deficient uroporphyrinogen decarboxylase

 

Typically, the workup of patients with a suspected porphyria is most effective when following a stepwise approach. See Porphyria (Acute) Testing Algorithm and Porphyria (Cutaneous) Testing Algorithm in Special Instructions or contact Mayo Medical Laboratories to discuss testing strategies.

 

There are 2 test options: PEE / Porphyrins Evaluation, Whole Blood and PEWE / Porphyrins Evaluation, Washed Erythrocytes. The whole blood option is easiest for clients but requires that the specimen arrive at Mayo Medical Laboratories within 7 days of draw. When this cannot be ensured, washed frozen erythrocytes, which are stable for 14 days, should be submitted.

Interpretation

Abnormal results are reported with a detailed interpretation which may include an overview of the results and their significance, a correlation to available clinical information provided with the specimen, differential diagnosis, and recommendations for additional testing when indicated and available.

Clinical Reference

1. Nuttall KL, Klee GG: Analytes of hemoglobin metabolism-porphyrins, iron and bilirubin. In Tietz Fundamentals of Clinical Chemistry. Fifth edition. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company, 2001, pp 584-607

2. Tortorelli S, Kloke K, Raymond K: Chapter 15: Disorders of porphyrin metabolism. In Biochemical and Molecular Basis of Pediatric Disease. Fourth edition. Edited by DJ Dietzen, MJ Bennett, ECC Wong. AACC Press 2010, pp 307-324

3. Anderson KE, Sassa S, Bishop DF, Desnick RJ: Disorders of Heme Biosynthesis: X-Linked Sideroblastic Anemia and the Porphyrias In The Online Metabolic and Molecular Bases of Inherited Disease. Edited by Valle D, Beaudet AL, Vogelstein B, et al. New York, McGraw-Hill, 2014. Accessed June 27, 2016. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971&Sectionid=62638866

4. Sassa S: Modern diagnosis and management of the porphyrias. Br J Haematol 2006;135:281-292

5. Whatley SD, Ducamp S, Gouya B, et al: C-terminal deletions in the ALAS2 gene lead to gain of function and cause X-linked dominant protoporphyria without anemia or iron overload. Am J Hum Genet 2008 Sep;83(3):408-414

Analytic Time

3 days (not reported on Saturday or Sunday)

Method Name

Spectrofluorometric

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical