Diagnostic profile of the AmplideX Fragile X Dx and Carrier Screen Kit for diagnosis and screening of fragile X syndrome and other FMR1-related disorders

Introduction: In 2009, a novel, CGG repeat primed FMR1 PCR assay was designed with primers flanking the triplet repeat region, as well as a third chimeric primer complementary to the (CGG)n repeat, that was capable of amplifying alleles throughout the repeat range. This assay for the first time allowed consistent detection of large full mutation alleles with PCR, resolution of heterozygosity in females and mapping of AGG interspersions. Areas Covered: The AmplideX Fragile X Dx and Carrier Screen Kit (Asuragen, Inc.) represents a refined assay that underwent validation with sensitivity analyses for FDA approval. Single-site precision, analytical sensitivity and specificity, limit of detection and diagnostic performance were assessed in comparison to reference methods at three independent sites. Single-site precision across all genotype categories showed 100% agreement at 20 ng input across multiple operators, days, instruments and kit lots. Compared to Southern Blot analysis, the overall percent agreement was over 98% for all expanded alleles. Expert Opinion: Limitations include no methylation assessment and hard to see full mutation peaks in some mosaic samples, but overall the assay is considered a highly accurate and time-efficient assay for FMR1 allele size determination.

Automated summary

The novel CGG repeat primed FMR1 PCR assay designed in 2009 allows consistent detection of large full mutation alleles, resolution of heterozygosity in females, and mapping of AGG interspersions. The AmplideX Fragile X Dx and Carrier Screen Kit has been validated for FDA approval, showing high accuracy and efficiency in determining FMR1 allele size. This assay is considered a highly accurate and time-efficient method for FMR1 allele size determination, with limitations including no methylation assessment and difficulty in detecting full mutation peaks in some mosaic samples.