27. A Novel, MS/MS Assay to Detect Hexosaminidase Activity in Tay-Sachs and Sandhoff Disease Using Dried Blood Spots
Tue 12:18 PM - PosterSplash Track 3
Michele Etter
University of Saskatchewan
Patricia Hall, Saskatchewan Disease Control Laboratory and The University of Saskatchewan
Jeff Eichhorst, Saskatchewan Disease Control Laboratory
Michele Etter, Saskatchewan Disease Control Laboratory
Michael H Gelb, University of Washington
Denis C Lehotay, Saskatchewan Disease Control Laboratory and The University of Saskatchewan
An assay was developed to use MS/MS for detecting Tay-Sachs and Sandhoff disease using dried blood spots (DBS). Tay-Sachs and Sandhoff diseases are caused by a deficiency of the enzyme Hexosaminidase (Hex A) and Hex A and B, respectively.

Two enzyme substrates were synthesized and used for the assay, one for the measurement of total Hex, and a deuterated version for Hex B. An incubation step to eradicate Hex A activity allows the measurement of Hex B alone. The deuterated substrate allows determination of both enzymes with one injection. Method development included optimizing buffers, incubation time, and MS/MS conditions.

The assay was tested using DBS from patients with Sandhoff disease, as well as unaffected controls of various ages. The relative percentage of Hex A increased in adult samples. Samples were analyzed to determine the presence of the disease in northern Saskatchewan, an area where the incidence of Sandhoff’s disease is higher than in the general population. Population normal ranges, age-related differences in enzyme activity, and loss of enzyme activity in stored DBS over time have been determined. The ability of the assay to differentiate heterozygotes from wild type is also being investigated. This new, MS/MS based assay allows for rapid detection of hexosaminidase enzyme deficiencies for both Sandhoff’s and Tay-Sach disease in DBS, making screening of newborns as part of a newborn screening program possible for the first time.

The generous support of Genzyme Corporation in acknowledged.