AccuCopy quantification combined with pre-amplification of long-distance PCR for fast analysis of intron 22 inversion in haemophilia A

Abstract

Background: To develop a digitalized intron 22 inversion (Inv22) detection in patients with severe haemophilia A.

Methods: The design included two tests: A genotyping test included two multiplex pre-amplification of LD-PCR (PLP) with two combinations of five primers to amplify wild-type and chimeric int22h alleles; a carrier mosaicism test was similar to the genotyping test except only amplification of chimeric int22h alleles by removing one primer from each of two combinations. AccuCopy detection was used to quantify PLP products.

Results: PLP product patterns in the genotyping test allowed identifying all known Inv22. Quantitative patterns accurately represented the product patterns. The results of 164 samples detected by the genotyping test were consistent with those obtained by LD-PCR detection. Limit of detection (LOD) of the carrier mosaicism test was at least 2% of heterozygous cells with Inv22. Performing the test in two obligate mothers with negative Inv22 from two sporadic pedigrees mosaic rates of blood and hair root of the mother from pedigree 1 were 8.3% and >20%, respectively and negative results were obtained in pedigree 2.

Conclusions: AccuCopy quantification combined with PLP (AQ-PLP) method was confirmed to be rapid and reliable for genotyping Inv22 and highly sensitive to carrier mosaicism detection.

Keywords: Factor VIII; Haemophilia A; Intron 22 inversion; Mosaicism.