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Test Code YALAD Aminolevulinic Acid Dehydratase, Whole Blood

Additional Codes

YALAD

Reporting Name

ALA Dehydratase, WB

Useful For

Preferred confirmation test for the diagnosis of aminolevulinic acid dehydratase deficiency porphyria

 

This test is not useful for detecting lead intoxication.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole blood


Ordering 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. Patient’s age is required

2. 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.

Container/Tube:

Preferred: Green top (sodium heparin)

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

Specimen Volume: Full tube 4 mL

Collection Instructions: Refrigerate specimen as soon as possible.


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Refrigerated (preferred) 7 days
  Ambient  4 days

Reference Values

Reference ranges have not been established for patients who are younger than 16 years of age.

 

≥4.0 nmol/L/sec

3.5-3.9 nmol/L/sec (indeterminate)

<3.5 nmol/L/sec (diminished)

Day(s) Performed

Thursday

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.

CPT Code Information

82657

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ALAD ALA Dehydratase, WB 12916-3

 

Result ID Test Result Name Result LOINC Value
4021 ALA Dehydratase 12916-3
28399 Interpretation 59462-2
606468 Reviewed By 18771-6

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.

Method Description

Measurement of aminolevulinic acid (ALA) dehydratase 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 days

Reject Due To

Gross hemolysis Reject

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 Name

Enzymatic End point/Spectrofluorometric

Forms

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:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)