[Evaluations of newborn screening program performance and enzymatic diagnosis of glucose-6-phosphate dehydrogenase deficiency in Guangzhou].

Objective: To reveal the molecular epidemiologic characteristics of glucose-6-phosphate dehydrogenase (G6PD) gene and to evaluate based on the genetic analysis the newborn screening program performance and enzymatic diagnosis of G6PD deficiency in Guangzhou. Methods: G6PD enzyme activities were measured by quantitative fluorescence assay in dry blood spots of 16 319 newborns(8 725 males, 7 594 females) 3-7 days after birth in Guangzhou Newborn Center. They were born in Guangzhou form Oct. 1 to 20, 2016. The cutoff value of G6PD was less than 2.6 U/g Hb in dry blood spots. G6PD deficiency was diagnosed when G6PD<1 700 U/L or G6PD/6PGD<1 in red blood cells. Genetic analysis of G6PD gene was performed on the dry blood spot samples of 823 newborns (including positive 346, negative 477)with various levels of G6PD enzyme activities through fluorescence PCR melting curve analysis(FMCA) to detect 15 kinds of mutations reported to be common among Chinese.G6PD gene Sanger sequency was performed in seven highly suspicious patients with negative results by FMCA. Results: (1) Using the cutoff value of G6PD< 2.6 U/g Hb , a total of 687(4.2%) newborns showed positive screening results, including 560 (6.4%) males and 127(1.7%) females. (2) Among the newborns with positive screening results, 214 males and 122 females were randomly chosen for G6PD gene analysis. The results showed that 197 (92.1%) males were hemizygote and 108(88.6%) females were mutation carriers with one to four alleles. Among the newborns with negative screening results, 41 males with G6PD 2.6-2.8 U/g Hb and 436 females with G6PD 2.6-4.5 U/g Hb were chosen for genetic analysis.Mutations were detected in 5(12.2%)boys, and 226(51.8%) girls were carriers.G6PD gene Sanger sequency of seven highly suspicious patients showed that c.406C>T, c.551C>T, c.835A>T hemizygote were found in 3 male's samples, respectively. (3) The estimated prevalence of harboring mutation was 6.0% in males and 13.5% in females according to rates of mutation in samples with various levels of G6PD enzyme activities. Six common mutations were c.1388G>A、c.1376G>T, c.95A> G, c.871G>A, c.1024C>T, c.392G>T, accounting for 95.5% of detected alleles .(4) based on results of G6PD gene analysis, the newborn scereening of G6PD deficiency with cutoff value G6PD<2.6 U/g Hb yielded a positive predict value(PPV) of 93.5%, a false-positive rate of 0.5%, and a sensitivity of 99.0% for males. A PPV of 88.5%, a false-positive rate of 0.2% . The prevalence of severe type G6PD deficiency in females was about 1.5%. Compared with to genetic analysis, the sensitivity and PPV of G6PD activity assay in red blood cells were 95.5%, 97.2%, respectively. Conclusions: The prevalence of G6PD deficiency in males was 6.0% in Guangzhou. Six mutations c.1388G>A, c.1376G>T, c.95A>G, c.871G>A, c.1024C>T, c.392G>T accounted for 95.5%. The cutoff value of G6PD<2.6 U/g Hb innewborn screening program and the criteria of biochemical diagnosis could accurately identify G6PD deficiency . Combined with biochemical and molecular analysis will improve the accuracy of diagnosis of G6PD deficiency and detect more heterozygous females.