NEW YORK (GenomeWeb) – Seoul, Korea-based firm BioCore will begin offering a digital PCR-based noninvasive prenatal test for fetal trisomy 21 this month in Korea. Although other groups have been developing similar tests, the firm claims to be the first in the world to commercialize a dPCR-based NIPT.
The market for noninvasive prenatal screening is growing, with guidelines in the US and abroad increasingly encouraging NIPT for average-risk as well as high-risk pregnancies. However, most commercial NIPT offerings rely on next-generation sequencing methods, which can be costly and time-consuming.
Moonju Oh, director of business development at BioCore, said that the company conducted pilot tests of its new assay with obstetrics and gynecology departments in hospitals in Korea last year. The firm uses the Bio-Rad QX200 for its T21 screening test and claims it costs about half as much as NGS-based tests, with potential turnaround times of one to two days, and requiring only 2 milliliters of maternal plasma.
In Korea, the NIPT market continues to grow, Oh said, and companies offering testing there, such as LabGenomics, Eone-Diagnomics Genome Center, and Theragen Etex, are using NGS-based methods. The criteria for screening include mothers over 35 years of age, and mothers with a history of fetal birth defects or other genetic diseases, Oh explained, noting that Korean guidelines specify that NIPT cannot be substituted for amniocentesis.
BioCore published a study earlier this year in Clinica Chimica Acta describing validation of the T21 screening assay using the Bio-Rad ddPCR system to detect four targets on chromosome 21. In the study, the firm first analyzed sheared DNA spiked into samples to set upper and lower limits, then moved to testing samples from pregnant women, showing an overall accuracy of 99.7 percent in 877 plasma samples.
BioCore was established in 2001 and the company has more than 100 employees, Oh said. It consists of a contract research organization and a biotechnology division. The CRO provides services such as biopharmaceutical development, biologic assay development, commercialization, preclinical and clinical research, and clinical trials management, he said, while the biotechnology division provides development of diagnostic kits and analysis service using genome technology.
In addition to the T21 test, BioCore has developed more than 50 molecular PCR and qPCR diagnostic kits that it supplies to hospitals in Korea. It also uses ddPCR and NGS to develop companion diagnostic test kits and cancer panels, Oh said.
The company chose to use the Bio-Rad QX200 Droplet Digital PCR System for its NIPT because the cost per test was lower than other options, according to Oh. The firm also preferred the number of samples that could be run simultaneously, the time to results, and the ease of confirming results, as well as the reproducibility of testing and analyses provided by the Bio-Rad system.
Other groups have worked on the problem of noninvasive prenatal screening, testing, and diagnosis using digital PCR in the past, although none appears to have yet commercialized the technology.
For example, a group of researchers in France described a multiplexed ddPCR test for T21 using the QX100 Droplet Digital PCR system that was "technically simple, relatively cheap, [and] easy to implement in a diagnostic setting" in a 2016 PLoS One study. The test was validated on plasma DNA samples from 213 pregnant women at high risk of chromosomal anomalies.
Like BioCore's test, the assay targeted several genes on the same chromosome with a multiplex of probes labeled with the same fluorophore in order to overcome the low levels of fetal DNA and increase the number of positive droplets for a given amount of input DNA.
Prior to that, a team that included Charles Cantor, the former CSO of Sequenom, as well as researchers in Hong Kong, described using digital PCR for detection of aneuploidy in a 2007 PNAS article.
On the other hand, researchers at Comprehensive Genetics, a US prenatal testing company, published a study modeling dPCR for T21 screening in 2012 that concluded a 20 percent fetal DNA enhancement would require 2,609 counts to achieve a 1 percent false-positive rate, which was "potentially feasible with readily available plates." But with only 2 percent fetal DNA, 110,000 counts would be needed to achieve a 5 percent false-positive rate, which was "far beyond current commercially available technology."
Digital PCR has also been applied to speed up testing of invasive samples. A study from the lab of Stephen Quake published in 2009 used amniocentesis and chorionic villus samples with a microfluidic digital PCR technique to detect T21, T18, and T13 in less than 6 hours.
Digital PCR has also been used for noninvasive prenatal testing beyond aneuploidy. For example, another Korean group published a paper in Scientific Reports in 2016 in which they applied the RainDrop Digital PCR technology, recently acquired by Bio-Rad, to NIPT to predict fetal genotype in autosomal recessive monogenic diseases that result from point mutations. And Quake co-authored work in 2014, describing a noninvasive ddPCR-based method to screen for methylmalonic acidemia in newborns.
Finally, while it is not digital PCR, there is a commercially available T21-only qPCR test from LifeCodexx called PrenaTest Option 1 that is currently available in Germany.
BioCore meanwhile has secured two patents on its test in Korea, Oh said, and has filed applications overseas. The firm is preparing to obtain CE marking and expects to market its test internationally in the future.