NEW YORK (GenomeWeb) — Quest Diagnostics launched an in-house developed noninvasive prenatal screening test for fetal chromosomal abnormalities in high-risk pregnancies today.
Quest has been offering the test, called QNatal Advanced, since April 13 through its Quest Diagnostics Nichols Institute in San Juan Capistrano, California. It replaces Sequenom's MaterniT21 Plus, which Quest had been offering after partnering with Sequenom last year.
At the time, Quest said it had also licensed intellectual property around NIPT from Sequenom and was planning to launch its own test in 2015.
QNatal Advanced analyzes cell-free DNA from maternal blood to screen for trisomies 21, 18, and 13. When a clear result is seen, it also reports on fetal sex aneuploidies, trisomies 16 and 22, and select microdeletions, including DiGeorge syndrome, Prader-Willi/Angelman syndromes, Jacobsen syndrome, Langer-Giedion syndrome, Cri-du-chat syndrome, Wolf-Hirschhorn syndrome, and 1p36 deletion syndrome.
The test, which relies on next-generation sequencing and runs on an Illumina platform, is available from 10 weeks of gestation and has a turnaround time of seven to 10 days or less.
QNatal, which targets women at high risk of fetal chromosomal abnormalities, will be similarly priced to MaterniT21 Plus, which Quest offered for approximately $2,800, a significant part of which is usually covered by health insurance. The test is currently available in all US states except for New York, where Quest is hoping to be able to offer it soon.
According to Douglas Rabin, Quest's medical director of women's health, QNatal Advanced differs from MaterniT21Plus in several aspects.
While both tests report on essentially the same conditions, with QNatal Advanced, women can opt out of obtaining information about fetal sex and microdeletions. Rabin told GenomeWeb that the company decided to offer the opt-outs because many patients do not want to learn their child's sex before birth, and because microdeletions occur only rarely and allow for limited interventions prior to birth. Many doctors consider the information "difficult to explain and less likely to happen, and therefore not necessary to include," he said.
Sequenom representatives, however, told GenomeWeb that the company also enables patients to opt out of reporting of fetal sex and microdeletions.
In addition, QNatal provides the relative amount of fetal DNA, or fetal fraction, Rabin said, an important factor for the accuracy of the test result. Sequenom measures fetal fraction as part of its test methodology but does not routinely include the number in its report, though it does provide fetal fraction upon request.
Finally, Quest uses a more recent Illumina sequencing chemistry, has made additional corrections for GC bias, and "brought some high-powered bioinformatics and statistics" to the analysis process, Rabin said.
QNatal provides yes/no answers for the presence or absence of chromosomal abnormalities, similar to Sequenom's reporting of positive/negative for trisomies, while other NIPT providers report risk scores instead.
Sensitivity and specificity of QNatal "will be comparable, potentially a little better" than for MaterniT21 Plus, Rabin said, and the test has a low no-call rate. So far, the company has used a fetal fraction cutoff around 4 to 5 percent, but based on preliminary data, "we potentially may be able to go below that," he said.
Quest representatives plan to present validation data for QNatal, including twin pregnancy data, at the International Federation of Gynecology and Obstetrics World Congress in Vancouver, British Columbia, in October, and some limited data at the European Cytogenetics Conference in Strasbourg, France in July. In addition, the company intends to publish results from its validation study in a peer-reviewed journal.
"We encourage all companies to provide their own validation data, since this is a laboratory-developed test which must be developed and validated independently by the laboratory performing the test," Sequenom told GenomeWeb, noting that for MaterniT21 Plus, it "openly provided the initial validation data and updated performance data for the test in our laboratory."
Rabin stressed that Quest considers QNatal Advanced a screening test, not a diagnostic test, and that the company offers invasive diagnostic testing, such as amniocentesis and chorionic villus sampling, to confirm positive results. Last year, Quest scientists published a paper in Genetics in Medicine that highlighted the significant false-positive rates of noninvasive prenatal tests, despite their high sensitivity and specificity.
Quest does not currently offer NIPT screening for average-risk pregnancies and will only consider doing so when guidelines by professional societies start recommending such testing. "Within our whole spectrum of testing, we are pretty comfortable right now with this high-risk [pregnancy] test," Rabin said.
"If compelling new science emerges suggesting that these technologies can be used diagnostically, or that the benefits of screening average-risk women outweigh the risks, we will certainly reconsider our position," he said in a statement.
And like other industry players, some of which have switched or are considering a switch to less expensive test platforms, such as microarrays or qPCR, the company is "always looking at ways to be more efficient at what we're doing, and to be better," Rabin said.