Determination of acid alpha-glucosidase protein: evaluation as a screening marker for Pompe disease and other lysosomal storage disorders.
BACKGROUND
In recent years, there have been significant advances in the development of enzyme replacement and other therapies for lysosomal storage disorders (LSDs). Early diagnosis, before the onset of irreversible pathology, has been demonstrated to be critical for maximum efficacy of current and proposed therapies. In the absence of a family history, the presymptomatic detection of these disorders ideally can be achieved through a newborn screening program. One approach to the development of such a program is the identification of suitable screening markers. In this study, the acid alpha-glucosidase protein was evaluated as a marker protein for Pompe disease and potentially for other LSDs.


METHODS
Two sensitive immunoquantification assays for the measurement of total (precursor and mature) and mature forms of acid alpha-glucosidase protein were used to determine the concentrations in plasma and dried blood spots from control and LSD-affected individuals.


RESULTS
In the majority of LSDs, no significant increases above control values were observed. However, individuals with Pompe disease showed a marked decrease in acid alpha-glucosidase protein in both plasma and whole blood compared with unaffected controls. For plasma samples, this assay gave a sensitivity of 95% with a specificity of 100%. For blood spot samples, the sensitivity was 82% with a specificity of 100%.


CONCLUSIONS
This study demonstrates that it is possible to screen for Pompe disease by screening the concentration of total acid alpha-glucosidase in plasma or dried blood spots.
Umapathysivam
K
K
Lysosomal Diseases Research Unit and State Screening Services, Department of Chemical Pathology, Women's and Children's Hospital, 72 King William Rd., North Adelaide, South Australia 5006, Australia.
Whittle
A M
AM
Ranieri
E
E
Bindloss
C
C
Ravenscroft
E M
EM
van Diggelen
O P
OP
Hopwood
J J
JJ
Meikle
P J
PJ
D015415:Biomarkers / Q000097:blood; D001800:Blood Specimen Collection; D004796:Clinical Enzyme Tests; D005087:Glucan 1,4-alpha-Glucosidase / Q000097:blood*; D006009:Glycogen Storage Disease Type II / Q000175:diagnosis* / Q000201:enzymology; D006801:Humans; D007118:Immunoassay; D007231:Infant, Newborn; D016464:Lysosomal Storage Diseases / Q000175:diagnosis* / Q000201:enzymology; D012680:Sensitivity and Specificity; D000520:alpha-Glucosidases
D015415:Biomarkers; D000520:alpha-Glucosidases; D005087:Glucan 1,4-alpha-Glucosidase