Ordering Guidance

This test is for diagnosis of acute intermittent porphyria. Porphobilinogen deaminase, also known as hydroxymethylbilane synthase and uroporphyrinogen I synthase, is commonly confused with uroporphyrinogen III synthase, the enzyme deficient in congenital erythropoietic porphyria.

Necessary Information

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

2. Patient's age is required

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

Specimen Required

Patient Preparation: For 24 hours before specimen collection, patient must not consume any alcohol. This is essential as ethanol induces porphobilinogen deaminase activity, which may lead to a false-normal result.

Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: Lavender top (EDTA) or green top (lithium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: Entire washed erythrocyte suspension

Collection Instructions:

Collect and process whole blood specimen as follows:

1. Transfer entire specimen to a 12-mL graduated centrifuge tube.

2. Centrifuge specimen at 4° C for 10 minutes at 2000 rpm.

3. Record volume of packed cells and the total volume of the specimen.

4. Discard supernatant plasma.

5. 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 2000 rpm, discarding supernatant after each washing.

6. Resuspend packed cells to the original total volume with 0.9% saline. Invert specimen gently to mix.

7. Transfer washed erythrocytes into a plastic vial and freeze.