Assays / Genetic Enzymes/ Amino Acid And Organic Acid Disorders

There are many amino acid and organic acid disorders of man, some quite familiar but others less so. These diseases are being diagnosed with increasing frequency as methods for urinary and plasma amino acid and organic acid analysis become more widely available and sophisticated. The SAS laboratory offers a battery of confirmatory enzyme assays for some of the most well known of the disorders, including urea cycle defects, homocystinuria and disorders of propionate metabolism. Details are given below. Prenatal diagnosis for some of the most severe disorders is available.

Specimen Requirements (specimen requirements for specific assays/diseases are given under their separate entries)

The Laboratory Recommends Use Of A Courier Service Or Royal Mail Special Delivery For Sending All Specimens To The Laboratory.

Specimen requirements: The essential specimen for most amino acid and organic acid disorders is a skin biopsy for establishment of a fibroblast culture, although a preliminary diagnosis can sometimes be obtained by assay of white cells.

Skin biopsies should be collected aseptically into a sterile bottle containing tissue culture medium (available from the laboratory), and sent at room temperature to arrive within 24 hours.
Biopsies for tissue culture should not be frozen.

Fibroblast cultures established in other laboratories should be sent in plastic 25 cm² flasks filled with medium.

Liver biopsies for assay of carbamoyl phosphate synthetase (CPS) and ornithine transcarbamylase (OTC) (5-10mg) should be snap-frozen in liquid nitrogen and transported to the laboratory in liquid nitrogen or solid CO₂. ADVANCE NOTICE OF ARRIVAL OF THESE BIOPSIES IS REQUIRED.

Chorionic villous biopsies should be delivered to the laboratory in sterile culture medium at ambient temperature.

Amniotic fluid should be sent in a sterile Universal container at ambient temperature.

It Is Essential That The Laboratory Is Contacted To Discuss The Case Before Chorionic Villi And Amniotic Fluid Specimens Are Sent.

 Amino Acid And Organic Acid Disorders For Which Tests Can Be Carried Out:

• Urea cycle defects
• Disorders of sulphur amino acid metabolism
• Disorder of branched-chain amino acid metabolism
• Disorders of organic acid metabolism

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