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Test ID: ALAD Aminolevulinic Acid Dehydratase, Whole Blood

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.

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 (PBG) 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 7 cases described in the literature since 1979.


The workup of patients with a suspected porphyria is most effective when following a stepwise approach. See Porphyria (Acute) Testing Algorithm in Special Instructions or call 800-533-1710 to discuss testing strategies.


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.

Testing Algorithm

The following algorithms are available in Special Instructions:

-Porphyria (Acute) Testing Algorithm

-Porphyria (Cutaneous) Testing Algorithm

-The Heme Biosynthetic Pathway

Report Available

2 to 4 days

Day(s) Performed

Tuesday, Thursday

Clinical Reference

1. 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

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

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 D Valle, AL Beaudet, B Vogelstein, et al. McGraw-Hill, Accessed August 9, 2017 Available at

Method Name

Enzymatic End point/Spectrofluorometric

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 PBDB / Lead with Demographics, Blood.

Necessary Information

Include a list of medications the patient is currently taking.

Specimen Required

Patient Preparation: Abstinence from alcohol is essential for at least 24 hours prior to specimen collection as ethanol suppresses aminolevulinic acid dehydratase (ALAD) activity, leading to false-positive results.


Preferred: Green top (sodium heparin)

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

Specimen Volume: Full tube 4 mL

Collection Instructions: Immediately place specimen on wet ice.

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 <16 years of age.


≥4.0 nmol/L/sec

3.5-3.9 nmol/L/sec (indeterminate)

<3.5 nmol/L/sec (diminished)

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 US Food and Drug Administration.

CPT Code Information


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


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 in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Neuromuscular, mml-Pediatric