title: Improved assay for differential diagnosis between Pompe disease and acid α-glucosidase pseudodeficiency on dried blood spots.
abstract: The high frequency (3.3-3.9%) of acid α-glucosidase pseudodeficiency, c.[1726G>A; 2065G>A] homozygote (AA homozygote), in Asian populations complicates newborn screening for Pompe disease (glycogen storage disease type II or acid maltase deficiency) on dried blood spots, since AA homozygotes have a considerably low enzyme activity. We observed that hemoglobin in the enzyme reaction solution strongly interferes with the fluorescence of 4-methylumbelliferone released from 4-methylumbelliferyl α-D-glucopyranoside (4MU-αGlc) by acid α-glucosidase. Therefore, we have searched for a method to effectively eliminate hemoglobin in the reaction solution. Hemoglobin precipitation with barium hydroxide and zinc sulfate (Ba/Zn method) carried out after the enzyme reaction considerably enhances the fluorescence intensity while it does not reduce the intensity to any extent as can occur with conventional deproteinization agents like trichloroacetic acid. The Ba/Zn method greatly improved the separation between 18 Japanese patients with Pompe disease and 70 unaffected AA homozygotes in a population of Japanese newborns in the assay with 4MU-αGlc on dried blood spots. No overlap was observed between both groups. We further examined acid α-glucosidase activity in fibroblasts from 11 Japanese patients and 57 Japanese unaffected individuals including 31 c.[1726G; 2065G] homozygotes, 18 c.[1726G; 2065G]/[1726A; 2065A] heterozygotes and 8 AA homozygotes to confirm that fibroblasts can be used for definitive diagnosis. The patients were reliably distinguished from three control groups. These data provide advanced information for the development of a simple and reliable newborn screening program with dried blood spots for Pompe disease in Asian populations.
authors.affiliation: Department of Biomedical Laboratory Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Shigeto
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Katafuchi
authors.forename: Yuya
authors.initials: Y
authors.lastname: Okada
authors.forename: Kimitoshi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Fumio
authors.initials: F
authors.lastname: Endo
authors.forename: Torayuki
authors.initials: T
authors.lastname: Okuyama
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Takeuchi
authors.forename: Marian A
authors.initials: MA
authors.lastname: Kroos
authors.forename: Frans W
authors.initials: FW
authors.lastname: Verheijen
authors.forename: Arnold J J
authors.initials: AJ
authors.lastname: Reuser
authors.forename: Toshika
authors.initials: T
authors.lastname: Okumiya
mesh_terms: D000328:Adult; D002648:Child; D004796:Clinical Enzyme Tests / Q000379:methods*; D005347:Fibroblasts / Q000378:metabolism; D006009:Glycogen Storage Disease Type II / Q000097:blood* / Q000175:diagnosis* / Q000201:enzymology / Q000235:genetics; D006403:Hematologic Tests / Q000379:methods*; D006720:Homozygote; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015997:Neonatal Screening; D000520:alpha-Glucosidases / Q000097:blood* / Q000172:deficiency / Q000235:genetics
chemical_list: C509951:GAA protein, human; D000520:alpha-Glucosidases