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Kings College Team Demonstrates Accuracy of Aria's T21 Test


This story was originally published Jan. 27.

In an independent, nested case-control study of 400 pregnant women conducted by researchers from King's College Hospital in the UK, Aria Diagnostics demonstrated that its targeted sequencing-based test to detect trisomy 21 accurately called all cases of trisomy 21 and 98 percent of trisomy 18 cases.

Detailing the results last week in the American Journal of Obstetrics and Gynecology, the researchers screened 400 pregnant women with a 1 in 300 risk or higher of carrying a fetus with trisomy. All women were in their first trimester, between 11 and 13 weeks of gestation, and were also screened by chorionic villous sampling.

The researchers correctly diagnosed all 50 trisomy 21 cases, as well as 49 out of 50 trisomy 18 cases with no false positives.

The company is planning to launch its test from its CLIA lab in San Jose, Calif., in the second half of this year, and is set to begin a clinical trial of the test in over 25,000 women (CSN 1/18/2012).

Aria uses a targeted sequencing approach in its internally developed assay, which it calls digital analysis of selected regions, or DANSR, that targets 384 loci each on chromosome 21 and chromosome 18. It previously described the method in Prenatal Diagnosis.

Because it targets just those two chromosomes, the King's College researchers said it requires one-tenth the sequencing as a massively parallel shotgun sequencing approach, such as is employed in Sequenom's MaterniT21 test. Additionally, 750 samples can be analyzed in one sequencing run, compared to the four to eight that have been tested with shotgun sequencing methods.

The AJOG study expands on the Prenatal Diagnosis study by also describing an algorithm, fetal-fraction optimized risk of trisomy evaluation, or FORTE, which combines maternal age-related risks with the risk computed from DANSR to give a "patient-specific odds of trisomy versus disomy" rather than a z-score, which sets a threshold for normal versus aneuploid based on the proportion of sequencing reads for chromosome 21 compared to chromosome 18.

Earlier this month, Aria's CEO Ken Song told Clinical Sequencing News that he does not believe that Aria's test infringes a patent Sequenom holds in the field — US Patent No. 6,258,540, "Non-invasive prenatal diagnosis" — because Aria uses a targeted sequencing approach rather than the shotgun sequencing approach used by Sequenom.

Nevertheless, Aria is both suing and being sued by Sequenom over the '540 patent (CSN 1/25/2012).

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