PRINCIPLE OF METHOD: Hydrolysis of the radiolabelled substrate [3H]-galactocerebroside (labelled in the galactose moiety) is followed by measuring release of [3H]-galactose which is determined by scintillation counting. The radiolabelled substrate is not available commercially and has to be prepared from unlabelled galactocerebroside.
USES AND LIMITATIONS OF THE METHOD: Deficiency of galactocerebrosidase is the primary defect in Krabbe disease (globoid cell leucodystrophy), and this disease (and some later-onset variants) can be diagnosed by demonstration of a severe deficiency in white cells or fibroblasts. Prenatal diagnosis can be achieved by showing a severe deficiency in chorionic villi or cultured amniotic cells. Heterozygote detection is not reliable and is not offered by the SAS laboratory.
The assay is included in our lysosomal enzyme screening procedure for patients with a neurodegenerative disorder.
SPECIMEN REQUIREMENTS: Blood. 5 ml lithium heparin (orange capped tube) unseparated and unfrozen. Send at room temperature to arrive at the laboratory within 24h of venepuncture. THE LABORATORY RECOMMENDS USE OF A COURIER SERVICE OR ROYAL MAIL SPECIAL DELIVERY FOR SENDING ALL SPECIMENS TO THE LABORATORY.