Pseudodeficiency alleles affect the newborn screening of glycogen storage disease typeⅡ / 中华检验医学杂志

ABSTRACT

Objective To investigate the effect of pseudodeficiency alleles on the newborn screening of glycogen storage disease typeⅡ(GSDⅡ) by using afluorometric enzymatic assay to determine acidα-glucosidase (GAA) activity in dried blood spot (DBS). Methods A total of 30507 newborns' DBSs, obtained from Newborn Screening Center of Xinhua Hospital Shanghai Jiao Tong University School of Medicine from May to December 2017, were screened for GSDⅡby fluorometric enzymatic assay of GAA activity. The suspected positive DBSs after the first and second screening were directly analyzed by Sanger sequencing of GAA to confirm the diagnosis. Retrospective analysis of 3172 controls without GSDⅡand 36 GSDⅡpatients were conducted to investigate the carrier status of pseudodeficiency alleles. Statistical analysis of frequency of pseudodeficiency alleles were carried out by Chi-square test or Fisher exact probability test. Results GAA activity of 30507 newborns showed a positively skewed distribution. Twenty-nine cases of newborns, suspected to be GSDⅡwere confirmed to be normal with genetic analysis of the original DBSs. Among the 29 suspected positive cases, 24 cases were homozygous for pseudodeficiency alleles c. [1726A/A; 2065A/A], and the other 5 cases were c. [1726G/A; 2065G/A] heterozygote. The frequency of c. 1726G>Ahomozygote in 3172 non-GSDⅡcontrols was 2.08％(66/3172), and c. 1726G>A homozygote occurred in allelic conjunction with c. 2065G>Ahomozygote. Frequency of c. [1726A; 2065A] haplotype in 3172 controls was 3.2％(206/6344). Frequency of c. [1726A/A;2065A/A] homozygote in 36 GSDⅡpatients (16.67％, 6/36) was significantly higher than that in non-GSDⅡcontrols(2.08％, 66/3172) (χ2=34.517, P<0.001). Conclusions Pseudodeficiency alleles show a high frequency in Chinese, which leads to a high false positive rate in the newborns screening of GSDⅡ.The afterword genetic analysis of the original DBS after the GAA activity screening could reduce the effect of pseudodeficiency alleles on the newborns screening of GSDⅡ.