Tay-Sachs and Sandhoff diseases: enzymatic diagnosis in dried blood spots on filter paper: retrospective diagnoses in newborn-screening cards.
BACKGROUND
Tay-Sachs disease (TSD), Sandhoff disease (SD) and variants are caused by deficient activity of the lysosomal enzymes hexosaminidase A (HA) and total hexosaminidase (TH) (hexosaminidase A plus B), respectively. For diagnosis, these enzymes are usually measured in plasma or extracts of leukocytes. We describe methods for the assay of hexosaminidase A and total hexosaminidase activities in dried blood spots (DBSs) on filter paper.


METHODS
We studied 163 healthy controls, 9 Tay-Sachs patients, 4 Sandhoff patients, 18 obligate carriers and the newborn-screening cards from two patients with Tay-Sachs and one patient with Sandhoff disease. To tubes containing a 3-mm-diameter blood spot, we added elution liquid and substrate solution. After incubation at 37 degrees C, the amount of hydrolyzed product was compared with a calibrator to allow the quantification of enzyme activity.


CONCLUSIONS
The described methodology is useful to distinguish patients with Tay-Sachs disease or Sandhoff disease from carriers and controls using samples that are sufficiently stable to be transported to the testing laboratory by mail. The diagnosis of both diseases from a newborn-screening card (NSC) was clearly demonstrated, even after storage for up to 38 months at room temperature. The newborn-screening card has been added to the biological materials that allow the identification of patients with Tay-Sachs disease and Sandhoff disease.
Chamoles
Néstor A
NA
Laboratory of Neurochemistry, Uriarte 2383, 1425, Buenos Aires, Argentina. nachamoles@fibertel.com.ar
Blanco
Mariana
M
Gaggioli
Daniela
D
Casentini
Carina
C
D000328:Adult; D005312:Fetal Blood / Q000201:enzymology; D006403:Hematologic Tests; D054818:Hexosaminidase A; D006801:Humans; D007231:Infant, Newborn; D015997:Neonatal Screening / Q000379:methods*; D012016:Reference Values; D012189:Retrospective Studies; D012497:Sandhoff Disease / Q000097:blood / Q000201:enzymology*; D013661:Tay-Sachs Disease / Q000097:blood / Q000201:enzymology*; D001619:beta-N-Acetylhexosaminidases / Q000097:blood
D054818:Hexosaminidase A; D001619:beta-N-Acetylhexosaminidases