Acid Alpha-Glucosidase, Blood Spot
Method Description Describes how the test is performed and provides a method-specific reference
Whole blood is collected on Protein Saver 903 (Whatman) filter paper and dried at room temperature. A one-eighth inch (3-mm) disk is punched out of the dried blood spots into a microcentrifuge tube. The extraction of blood from the blood spot using water takes place on an orbital shaker for 1 hour at 2 to 8 degrees C in a chilled shaker or cool room. A total of 40 mcL of the extracted sample is combined with 50 mcL of substrate A (40 mM sodium acetate, pH 3.8 with 1.4 mM 4-methylumbelliferyl-alpha-D-glucopyranoside [4-MUG]) and 10 mcL of 8 mcmol acarbose (acts as an inhibitor of leukocyte-derived alpha-glucosidase) in a black 96-well plate, in duplicate. Blanks that contain substrate and inhibitor only are also set up in duplicate with 2 wells used for each patient. The plate is sealed with aluminum sealer and incubated at 37 degrees C for 20 hours. The remaining extracts are also incubated at 37 degrees C for 20 hours. The plate is centrifuged at 600 g for 5 minutes to collect any condensation on the sealer. A total of 40 mcL of the leftover extracts are added to each of the corresponding "blank" wells for each patient. Finally, 200 mcL of stop buffer (150 mM EDTA, pH 11.4) is added to all wells. A calibration curve is set up on every plate to calculate results. (Chamoles NA, Niizawa G, Blanco M, et al: Glycogen storage disease type II: enzymatic screening in dried blood spots on filter paper. Clin Chim Acta 2004;347:97-102; Zhang H, Kallwass H, Young SP, et al: Comparison of maltose and acarbose as inhibitors of maltase-glucoamylase activity in assaying acid alpha-glucosidase activity in dried blood spots for the diagnosis of infantile Pompe disease. Genet Med 2006;8:302-306)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test