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Introduction ⬇

The primary porphyrins of erythrocytes are protoporphyrin, uroporphyrin, and coproporphyrin.

Fractionation of erythrocytes is used to differentiate congenital erythropoietic coproporphyria from erythropoietic protoporphyria and to confirm a diagnosis of protoporphyria. This test establishes a specific type of porphyria by naming the specific porphyrin in plasma. In persons with renal failure, plasma fractionation can help to determine whether the porphyria is caused by a deficiency of uroporphyrinogenic decarboxylase or by failure of the renal system to excrete porphyrinogens.

Normal Findings ⬆ ⬇

The value is reported in micrograms per deciliter (μg/dL). Check with your laboratory for reference values.

  1. Erythrocyte porphyrins

    1. Protoporphyrin: 16–60 μg/dL packed cells or 0.3–1.7 μmol/L

    2. Uroporphyrin: <2 μg/dL or <24 nmol/L

    3. Hepatocarboxylic: <1 μg/dL or <10 μg/L

    4. Hexacarboxylic: <1 μg/dL or <10 μg/L

    5. Pentacarboxylic: <1 μg/dL or <10 μg/L

    6. Coproporphyrin: <1 μg/dL or <15 μg/L

  2. Plasma porphyrins: Total porphyrins should not exceed 1.0 μg/dL or 12 nmol/L.

Procedure ⬆ ⬇

  1. Draw a 5-mL sample of anticoagulated (EDTA or heparin can be used) blood. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

  2. Protect the specimen from light.

Clinical Implications ⬆ ⬇

  1. Increased erythrocyte porphyrins are associated with primary porphyrias:

    1. Congenital erythropoietic protoporphyria

    2. Protoporphyria (autosomal dominant deficiency of heme synthetase)

    3. Hereditary porphobilinogen synthase deficiency

    4. Intoxication porphyria

  2. Increased plasma porphyrins are associated with:

    1. Congenital erythropoietic protoporphyria

    2. Coproporphyria

    3. Porphyria cutanea tarda

    4. Variegate porphyria

    5. CKD porphyria

Interventions ⬆

Pretest Patient Care

  1. Advise patient of test purpose and procedure.

  2. Note on the requisition any drugs the patient is taking.

  3. Before testing, discontinue drugs that are known to cause intermittent porphyria (after checking with the healthcare provider).

  4. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have the patient resume medications.

  2. Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for porphyria or lead poisoning.

  3. Caution persons diagnosed with porphyria (with cutaneous manifestations) to avoid sun exposure.

  4. Advise persons diagnosed with porphyria (with neurologic symptoms) that attacks can be precipitated by infections, stress, various phases of the menstrual cycle, fasting states, and certain drugs. A listing of drugs (not all inclusive) that may precipitate acute attacks follows:

    1. Barbiturates

    2. Chlordiazepoxide

    3. Chloroquine

    4. Chlorpropamide

    5. Diazepam

    6. Dichloralphenazone

    7. Ergot preparations

    8. Estrogens

    9. Ethanol

    10. Glutethimide

    11. Griseofulvin

    12. Hydantoins

    13. Imipramine

    14. Ketorolac

    15. Meprobamate

    16. Methsuximide

    17. Methyldopa

    18. Phenytoin

    19. Sulfonamides

  5. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Clinical Alert

  1. A blood test for uroporphyrinogen I synthase (also known as erythrocyte porphobilinogen deaminase) can be done to identify persons at risk for acute intermittent porphyria, to detect latent-phase intermittent porphyria, and to confirm the diagnosis during an acute episode.

  2. The normal value is 5.3–9.2 nmol/L in women; 3.4–8.5 nmol/L in men. A value of <3.5 nmol/L is diagnostic of acute intermittent porphyria.