1. Urinary aminolaevulinic acid (ALA) is increased in patients during acute attacks of hepatic porphyrias (AIP, HC, VP and ALA dehydratase deficiency) and also in lead poisoning but not in PCT, CEP or EPP.
2. Assessment of treatment of patients with acute porphyria, however quantitative PBG is the method of choice.
1. A normal ALA excretion in a patient with acute symptoms excludes acute porphyria as a cause of the symptoms.
2. Acute porphyria is extremely rare before puberty except in the homozygous acute hepatic porphyrias and ALA dehydratase deficiency.
3. This method is not recommended for the assessment of lead poisoning. The method of choice for this purpose is blood lead.
A fresh random urine specimen (preferably in a universal container) without preservative is required. Early morning specimens are preferred although a random specimen is acceptable if the creatinine is greater than 2mmol/L. 24hr collections are not recommended. Urine ALA levels decrease rapidly on exposure to light (the half life is 24hrs). There is no advantage in 24hr collections and some disadvantage including exposure to light, incomplete collections and bacterial growth.
The minimum volume required for assay is 2.0ml – allowing ALA quantitation and creatinine measurement. Paediatric investigations should be discussed with the laboratory.
Dispatch samples by first class post in a container that conforms to Post Office regulations, protected from light, to arrive in the laboratory with 24-48 hours of sampling. When a delay in dispatch is anticipated, due to weekend or bank holiday, samples should be stored frozen and protected from light.
Routine requests are assayed within 5 working days after receipt of sample. Urgent requests should be discussed with the laboratory and dispatched via a courier service. Results can be telephoned or faxed as soon as they become available.
Adults: < 3.8umol/mmol creatinine (Cardiff)
< 46umol/24hrs (King’s)
Children: < 5.2umol/mmol creatinine
Frontline tests for the investigation of suspected porphyria. A. C. Deacon & G. H. Elder. J. Clin. Pathol. 2001; 54:500-507