The determination of delta-aminolevulinic acid in the urine is used for the laboratory diagnosis and differential diagnosis of porphyria, a group of diseases with signs and symptoms affecting the skin and nervous system. It can also be used in laboratory testing of lead poisoning in children.
Delta-aminolevulinic acid (ALA) is the precursor for porphobilinogen (PBG), a substance used in hemoglobin heme formation. The following steps in the biochemical pathway of heme synthesis are Porphobilinogen → Urobilinogen III → Uroporphyrin III → Porphobilinogen III → Coproporphyrin III→ Protoporphyrinogen → Protoporphyrin. This process then leads to the formation of heme. If any problem arises in the biochemical pathway of heme formation, delta-aminolevulinic acid accumulates and is excreted in the urine. Delta-aminolevulinic acid is not usually present in urine.
Delta-aminolevulinic acid concentrations in urine are significantly increased in many patients with acute neurological forms of porphyria. Screening for delta-aminolevulinic acid may be required in patients with symptoms that indicate acute porphyria, such as abdominal pain, nausea, constipation, peripheral neuropathy, muscle weakness, urinary retention, confusion, and hallucinations.
The presence of delta-aminolevulinic acid in the urine may additionally indicate lead poisoning. The test can be used as a pre-screening test to detect excessive lead absorption well before symptoms occur, especially in children.
Possible Interpretations of Pathological Values
- Increase: Acute porphyria, alcohol abuse, hepatitis, liver cancer, lead exposure, lead poisoning. Medications: barbiturates, griseofulvin, penicillin, rifampicin.
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