Prenatal BoBs, a more informative option than FISH and QF-PCR for IVD labs
Prenatal BoBs™ is a CE-marked IVD product based on BACs-on-Beads technology. In addition to detecting copy number changes of chromosomes 13, 18, 21, X and Y, the product enables detection of 9 additional chromosomal regions in which a clear correlation between a loss and an adverse outcome has been demonstrated.1 Copy number changes in these targeted microdeletion regions are not easily found with other commonly used methods. Also the microdeletion syndromes detected by Prenatal BoBs often are not inherited and do not display ultrasound abnormalities, so they may otherwise be missed in a prenatal setting.
Fast and targeted molecular karyotyping with new, revolutionary PerkinElmer technology BACs-on-Beads™
BACs are Bacterial Artificial Chromosomes, large cloned sequences of human DNA, typically 170,000 bases long. BACs have long been used for fluorescent in situ hybridization (FISH). BACs-on-Beads is a technology where DNA probes generated from selected BACs are immobilized onto Luminex® encoded beads. The resulting bead sets are used to assay for chromosomal gains and losses from minute sample amounts with high throughput.
A BACs-on-Beads bead set can contain up to 98 different BACs-on-Beads probes targeted to various regions of the human genome. In addition 2 non-homologous oligonucleotide beads are used for background subtraction.
Sample and reference DNAs are enzymatically labeled with biotin. The enzymatic labeling step provides significant amplification of the sample and therefore small DNA amounts can be used as input. BACs-on-Beads analysis comprises hybridization of the purified biotin labeled DNA to BACs-on-Beads probes representing the specific targeted sequences. Post hybridization a fluorescent streptavidin-phycoerythrin reporter is added and bound to the biotin labels. The relative amount of fluorescent DNA bound to the beads is determined using a Luminex instrument system and BoBsoft™ analysis software.
BoBsoft performs normalization of data measured from each sample with respect to data from the male and female references. All samples are compared to both male and female references, so the sex of the sample does not need to be known prior to the assay. Normal diploid loci generate ratios of 1.0. Single copy gains generate ratios of 1.3 to 1.4, and single-allele deletions generate ratios of 0.6 to 0.8. Reliability in the result is achieved by having carefully selected the probes used as well as by having several probes covering a chromosomal region generally deflecting together if a gain or loss has occurred in this region.
Luminex® xMAP® Technology is an established multiplexing technology utilizing approximately 5 μm diameter polystyrene beads coded with two different fluorescent dyes.
By using ten different concentrations of each of the two dyes it is possible to generate up to 100 bead types with distinct fluorescent signatures that can be identified through excitation of the coded dyes by the Luminex 100/200™ instrument.
This allows for a high-throughput, cost-effective multiplexing technology to be implemented in cytogenetic laboratories.
BoBsoft 2.0 provides data presentation of panel multiplex genomic gain/loss assays. The new features for the application are highlighted below.
New BoBsoft 2.0 Features:
New Calculation Algorithm and Computed Reference options
- Users can now choose between the Ratio or Principle Component algorithms, as well as new reference choices (computed and accumulated computed). These options help provide better results when dealing with ‘noisy’ data sets.
- Historical QC data is now stored to allow monitoring of assay performance and trends
- Accumulated computed references can also be stored
- Database Management allows for archiving of the current database to allow accumulation of new data points.
Workflow and User Experience Improvements
- Automatic BoBs assay panel detection is available when importing results
- The summary pages and report formats are improved
- User logins are now available as well as extra security and privileges for admins.