摘要目的 探讨假性缺陷等位基因携带情况对荧光法检测干血滤纸片酸性α-葡萄糖苷酶(GAA)活性进行新生儿糖原贮积病Ⅱ型(GSDⅡ)筛查的影响.方法 对2017年5至12月上海交通大学医学院附属新华医院新生儿疾病筛查中心的30507份新生儿干血滤纸片(dried blood spot,DBS)通过荧光法检测其酸性α-葡萄糖苷酶(GAA)活性进行GSDⅡ筛查,对筛查疑似阳性新生儿原DBS经GAA基因分析确认其基因突变及假性缺陷等位基因的携带情况.回顾性分析3172例非GSDⅡ人群和36例GSDⅡ患者中假性缺陷等位基因携带情况,采用卡方检验或Fisher确切概率法对假性缺陷等位基因携带频率进行数据统计分析.结果 30507份新生儿DBS标本GAA酶活性呈正偏态分布,初次和二级筛查检出29例新生儿疑似阳性,GAA基因分析未发现GSDⅡ患者,但该29例中24例携带纯合假性缺陷等位基因c.[1726A/A;2065A/A],5例携带杂合假性缺陷等位基因c.[1726G/A;2065G/A].3172例非GSDⅡ人群中假性缺陷等位基因c.1726G>A纯合子频率为2.08％(66/3172),当c.1726 G>A纯合突变时,同时发生c.2065 G>A纯合突变频率为100％(66/66),c.[1726A;2065A]单倍体型频率为3.2％(206/6344).36例GSDⅡ患者中6例(16.67％,6/36)携带纯合假性缺陷等位基因c.[1726A/A;2065A/A],显著高于非GSDⅡ人群(2.08％,66/3172)(P<0.001,χ2=34.517).结论 假性缺陷等位基因在中国人群中携带率较高,可导致荧光法检测GAA酶活性进行新生儿GSDⅡ筛查的假阳性率升高,新生儿筛查后对原干血滤纸片的基因检测可降低其对新生儿筛查的影响.

abstractsObjective 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.&nbsp;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.