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HelpTest Code ALADW Aminolevulinic Acid Dehydratase, Washed Erythrocytes
Reporting Name
ALA Dehydratase, RBCUseful For
Confirmation of a diagnosis of aminolevulinic acid dehydratase deficiency porphyria using washed erythrocyte specimens
This test is not useful for detecting lead intoxication.
Testing Algorithm
The following algorithms are available:
-Porphyria (Acute) Testing Algorithm
Method Name
Enzymatic End point/Spectrofluorometric
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Washed RBCOrdering Guidance
This assay is not useful in assessment of lead intoxication as it reactivates aminolevulinic acid dehydratase that has been inhibited by lead. The preferred test for lead toxicity is PBDV / Lead, Venous, with Demographics, Blood.
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: Patient must not consume any alcohol for 24 hours before specimen collection. This is essential as ethanol suppresses aminolevulinic acid dehydratase activity, leading to false-positive results.
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.
Specimen Minimum Volume
1 mL of washed and resuspended erythrocytes
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Washed RBC | Frozen (preferred) | 7 days | |
| Refrigerated | 14 days | ||
| Ambient | 4 days |
Reject Due To
| Cell suspension not available | Reject |
Special Instructions
Reference Values
Reference ranges have not been established for patients who are younger than 16 years.
≥4.0 nmol/L/sec
3.5-3.9 nmol/L/sec (indeterminate)
<3.5 nmol/L/sec (diminished)
Day(s) Performed
Thursday
CPT Code Information
82657
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| ALADW | ALA Dehydratase, RBC | 2813-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 31946 | ALA Dehydratase | 2813-4 |
| 31948 | Interpretation | 59462-2 |
| BG573 | Total Cell Suspension | 94496-7 |
| BG574 | Packed Cell Volume | 94497-5 |
| 606469 | Reviewed By | 18771-6 |
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.Genetics Test Information
Aminolevulinic acid dehydratase (ALAD) activity is inhibited in other situations including hereditary tyrosinemia type 1, lead intoxication, and exposure to styrene, trichloroethylene, or bromobenzene. These causes should be ruled out when considering a diagnosis of ALAD deficiency porphyria. This method will not detect a decreased ALAD enzyme activity due to lead intoxication.
This test will not detect lead intoxication.
Clinical Information
Porphyrias are a group of inherited disorders resulting from enzyme defects in the heme biosynthetic pathway. A defect in the second enzyme of this pathway causes 5-aminolevulinic acid (ALA) dehydratase (ALAD) deficiency porphyria (ADP). A marked deficiency of ALAD causes the accumulation and subsequent urinary excretion of large amounts of ALA. Urinary porphobilinogen remains essentially normal, which rules out other forms of acute porphyria.
ADP is an autosomal recessive acute hepatic porphyria that produces neurologic symptoms similar to those seen in acute intermittent porphyria. Symptoms include acute abdominal pain, peripheral neuropathy, nausea, vomiting, constipation, and diarrhea. Respiratory impairment, seizures, and psychosis are possible during an acute period. ADP is extremely rare with only 8 cases described in the literature since 1979.
The workup of patients with a suspected porphyria is most effective when following a stepwise approach. Molecular confirmation is available; order CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies; specify ALAD Gene List ID: IEMCP-D81317. See Porphyria (Acute) Testing Algorithm or call 800-533-1710 to discuss testing strategies.
Interpretation
Abnormal results are reported with a detailed interpretation including 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.
Cautions
False-positive values may result from enzyme degradation due to improper specimen handling. It is essential to adhere to instructions outlined in the Specimen Required and the Specimen Stability Information fields.
Method Description
Measurement of aminolevulinic acid (ALA) dehydratase (ALAD) activity is based on the rate of synthesis of uroporphyrin from ALA in incubated, lysed erythrocytes. Low yield of uroporphyrin from ALA indicates a deficiency of ALAD.(Unpublished Mayo method)
Report Available
2 to 8 daysSpecimen Retention Time
14 daysForms
New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available: