Effect of sample collection, temperature and time of storage on β-galactosidase and total hexosaminidase activities in dried blood collected on filter paper.

BACKGROUND

Dried blood spots (DBS) on filter paper is a valuable sampling technique in clinical chemistry, but the stability of enzymes used in the diagnosis of lysosomal storage diseases (LSDs) needs to be evaluated.

METHODS

In a first experiment, blood from 20 subjects was collected using a syringe without additives and distributed into EDTA tubes, heparin tubes, and spotted on filter paper for the comparison of sampling effects. In a second experiment, blood from 30 healthy subjects was spotted on filter paper and analyzed for β-galactosidase and total hexosaminidase activities after storage of the samples at different temperatures for up to 180 days.

RESULTS

Initially, we observed that enzyme activities were the same, independent of the collection method. When DBS was stored at 37°C the activity of β-galactosidase dropped to 85% of the initial value after 180 days (p<0.05). At all other temperatures (-20°C, 4°C and 25°C), the results were within the methodological error. Total hexosaminidase activity did not change significantly during the entire study period and at different storage temperatures.

CONCLUSIONS

The two enzymes investigated in the present study may be stored for up to 17 days (β-galactosidase) or 180 days (total hexosaminidase) until analysis without loss of activity.