BACs-on-Beads Technology: A Reliable Test for Rapid Detection of Aneuploidies and Microdeletions in Prenatal Diagnosis

Abstract

The risk of fetal aneuploidies is usually estimated based on high resolution ultrasound combined with biochemical determination of criterion in maternal blood, with invasive procedures offered to the population at risk. The purpose of this study was to investigate the effectiveness of a new rapid aneuploidy screening test on amniotic fluid (AF) or chorionic villus (CV) samples based on BACs-on-Beads (BoBs) technology and to compare the results with classical karyotyping by Giemsa banding (G-banding) of cultured cells in metaphase as the gold standard technique. The prenatal-BoBs kit was used to study aneuploidies involving chromosomes 13, 18, 21, X, and Y as well as nine microdeletion syndromes in 321 AF and 43 CV samples. G-banding of metaphase cultured cells was performed concomitantly for all prenatal samples. A microarray-based comparative genomic hybridization (aCGH) was also carried out in a subset of samples. Prenatal-BoBs results were widely confirmed by classical karyotyping. Only six karyotype findings were not identified by Prenatal-BoBs, all of them due to the known limitations of the technique. In summary, the BACs-on-Beads technology was an accurate, robust, and efficient method for the rapid diagnosis of common aneuploidies and microdeletion syndromes in prenatal samples.

Application of the BACs‐on‐Beads™ assay for rapid prenatal detection application of BoBs™ for PND of aneuploidies and microdeletions

“…These cases all involved microdeletions or microduplications, which conventional karyotyping might not be able to detect because they are less than 5 Mb in size—the resolution limit of the method, unless the banding is above the 750‐band level (Choy et al, ); indeed, false‐negative diagnoses occurs most often in karyotyping when the abnormality is less than 5 Mb (Shaffer & Bui, ). Thus, from a cytogenetic point of view, the BoBs™ assay could offer extra diagnostic benefits compared with karyotyping because it provides more diversity and sensitivity to detect microdeletions and microduplications (Garcia‐Herrero et al, ; Rosenfeld et al, ; Sheath, Duffy, Asquith, Love, & George, ).…”

“…Additional molecular and classical cytogenetic methods that evaluate uncultured samples were developed to rapidly (in 48 hr) exclude recurrent aneuploidies for chromosomes 13, 18, 21, and X/Y of foetal chromosome unbalances (Grati et al, ; Mann et al, ; Shaffer & Bui, ). In some countries, these rapid and cheaper methods are the only techniques used to diagnose cases involving advanced maternal age or increased risk after maternal screening (Garcia‐Herrero et al, ); however, even these methods have limitations.…”

“…The BACs‐on‐Beads TM (BoBs™) assay was recently introduced for detecting common aneuploidies and specific microdeletion syndromes (Choy et al, ; Garcia‐Herrero et al, ; Gross et al, ; Shaffer et al, ). This multiplex assay uses beads impregnated with different concentrations of two different fluorochromes to create an array of up to 100 different unique probes; each probe is derived from a bacterial‐artificial chromosome (BAC) DNA, which currently allows for the diagnosis of common trisomies and nine microdeletions within 24 hr (Lakovschek, Streubel, & Ulm, ; Vialard et al, ).…”

Utility and performance of bacterial artificial chromosomes‐on‐beads assays in chromosome analysis of clinical prenatal samples, products of conception and blood samples

“…Concordance of Prenatal BoBs results with KT/FISH results for common aneuploidies is consistent with earlier reports. 1 Prenatal BoBs can be reported within 2 days from receipt of sample, and this is essential to reduce maternal anxiety and facilitate timely clinical decisions. 27 Prenatal BoBs circumvents two main limitations of KT, higher TAT and detection of the nine microdeletion syndromes.…”

“…The risk of fetal aneuploidies for chromosomes 21, 18 and 13 is usually estimated using ultrasound scan (nuchal translucency) in combination with various biochemical markers. 1,2 Since the past few years, non-invasive prenatal testing (NIPT) is increasingly being used to screen for aneuploidies of chromosomes 21, 18 and 13, sex chromosome aneuploidies and some microdeletions. 3,4 More recently, NIPT has been reported to screen for aneuploidies of all the chromosomes and also sub-chromosomal aberrations.…”