Performance evaluation study of ID RHD XT, a new genotyping assay for the detection of high-prevalence RhD negative and weak D types.

BACKGROUND AND OBJECTIVES: Routine serologic D typing does not distinguish between weak D subtypes and partial D phenotypes. The goal of this study was to validate the performance of the ID RHD XT genotyping assay. MATERIAL AND METHODS: Previously serotyped samples for D antigen (n = 1000; 16% weak D serotyped donors) were analysed. The reference methods used for comparison were licensed serology tests for D antigen phenotype, and bidirectional sequencing (BDS) for weak D type confirmation and HPA-1 phenotype prediction. Discrepancies were solved with BDS and BLOODchip® Reference. RESULTS: There were no system failure, a 100% call rate and no inconclusive results. ID RHD XT correctly called all (88/88) weak D types 1, 2 and 3. Review of other 87 apparent discrepancies identified a small number of serology errors and showed that ID RHD XT correctly signalled the presence of other RHD variants which were further confirmed by BDS and BLOODchip® Reference. The predicted HPA-1 phenotype by ID RHD XT was 100% concordant with BDS. CONCLUSION: ID RHD XT genotype predictions for high-prevalence RhD negative and weak D types 1, 2 and 3 as well as for HPA-1a/HPA-1b antigens were accurate, which is of clinical significance in guiding transfusion needs.

A DNA microarray for the detection of point mutations and copy number variation causing familial hypercholesterolemia in Europe.

To facilitate genetic cascade screening for familial hypercholesterolemia (FH) in Europe, two versions (7 and 9) of a DNA microarray were developed to detect the most frequent point mutations in the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin 9 (PCSK9) genes. The design of these microarrays is based on LIPOchip, version 4, which detects 191 LDLR and APOB mutations identified in Spanish patients with FH. A major improvement of LIPOchip, versions 7 and 9, is the ability to detect copy number variation (deletions or duplications of entire exons) in LDLR, thus abolishing the need to perform multiplex ligase-dependent probe amplification in patients with FH. The aim of this study was to validate a tool capable of detecting point mutations and copy number variations simultaneously and to evaluate its use and the newly developed software for analysis in clinical practice by reanalysis of several patients with known mutations causing FH. With the help of these validations, several aspects were analyzed, improved, and implemented in a newer version, which was evaluated through an internal validation.