Extended newborn screening using DNA methylation testing for fragile X syndrome in 17,107 infants

There is interest in newborn screening for fragile X syndrome (FXS) because of the potential benefits of early diagnosis and treatment and the prevention of future affected births through informed reproductive choices. This study examined the feasibility of newborn screening for FXS on a population scale.

Methylation-specific quantitative melt analysis (MS-QMA) of FMR1 was used for first-tier screening of newborn blood spots (NBS) from a population sample of 17,107 infants, with sex confirmed using real-time polymerase chain reaction. EpiTYPER system methylation analyses and AmpideX cytosine-guanine-guanine (CGG) sizing polymerase chain reaction were performed on MS-QMA-positive newborn blood spots.

Following first-tier testing, methylation results suggestive of FXS were detected in 3 males and 36 females. AmplideX and EpiTYPER second-tier testing confirmed a diagnosis of FXS in 2 males and identified a full mutation in 1 female. One male was confirmed to have abnormal methylation by EpiTYPER testing, with a 22 CGG allele detected by AmplideX. Two females with abnormal methylation had an FMR1 premutation (55-158 CGG repeats) that does not cause FXS.

MS-QMA was a feasible first-tier newborn screening test in both sexes, with 3 infants showing confirmatory testing results consistent with FXS identified out of 17,107 infants screened.