Type of test Urine (24-hour)
Normal findings
1.5-7.5 mg/24 hr or 11-57 μmol/24 hr (SI units)
Possible critical values
> 20 mg/24 hr
Test explanation and related physiology
As the basic precursor for the porphyrins, d-ALA is needed for the normal production of porphobilinogen, which ultimately leads to heme synthesis in erythroid cells. Heme is used in the synthesis of hemoglobin. Genetic disorders (porphyria) are associated with a lack of a particular enzyme vital to heme metabolism. These disorders are characterized by an accumulation of porphyrin products in the liver or red blood cells. Acute intermittent porphyria (AIP) is the most common form of the liver porphyrias.
In lead intoxication, heme synthesis is similarly diminished by the inhibition of ALA dehydrase. This enzyme assists in the con version of ALA to porphobilinogen. As a result of lead poisoning, ALA accumulates in the blood and urine.
Interfering factors
* Drugs that may cause increased ALA levels include barbiturates, griseofulvin, and penicillin.
Procedure and patient care
• See inside front cover for Routine Urine Testing.
• Keep the urine in a light-resistant container with a preservative.
• If the patient has a Foley catheter in place, cover the drainage bag to prevent exposure to light.
Abnormal findings
Increased levels
- Porphyria
- Lead intoxication
- Chronic alcoholic disorders
- Diabetic ketoacidosis
