Sequenom revises test accuracy downward; Stock falls
February 4th, 2009From San Diego Business Journal, AP/Forbes.com:
The stock price of Sequenom Inc. fell 7.2 percent Tuesday after the company said its noninvasive prenatal genetic test was not as effective as it had previously reported.
In previously reported data, Sequenom said its SEQureDx prenatal screening technology came up with one false positive result, meaning a woman could be told her unborn baby had Down syndrome when, in reality, it did not. That put its accuracy at 99.9 percent overall. Its latest data shows additional false positive results, amounting to 96.6 percent accuracy. Both times, its technology correctly identified 100 percent of the negative results.
Overall, the company has reported results in 858 women.
Sequenom’s data to date is based on a very small sample size, and has not been reviewed by scientists nor published in a medical journal. The company has said it plans to begin marketing the test directly to consumers later this year. FDA approval of the test is not required.
The company has estimated that the market for prenatal testing for chromosomal disorders like Down syndrome could be $3 billion to $5 billion or more worldwide.
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February 4th, 2009 at 8:36 am
Statistics can always be tricky, and interpreting them even more challenging. In fact, Sequenom recently had to revise its own press release after some numbers did not add up. Here are the accurate statistics so far, based on very small self-reported data from Sequenom:
- The test is 100% accurate (or 100% sensitive), meaning that all fetuses with Down syndrome were correctly picked up by the test.
- If a pregnant women receives a positive result, there is a 97% chance that her fetus actually has Down syndrome (this is known as the “positive predictive value” and takes into account the one false positive result now reported.)
- If a pregnant women receives a negative results, there is a 100% chance that her fetus does not have Down syndrome (this is known as the “negative predictive value” and takes into account that there have been no false positive results reported.)