Nguyen, of Consumer Genetics, said the Pink or Blue test is more sensitive than the one used in Italy because it looks for a DNA marker that is 100 times bigger.
"There's more of it, so it's easier to spot," Nguyen said. For competitive reasons, she wouldn't give any specifics about the particular sequence of male DNA that the company searches for.
She didn't know how many customers had complained of an incorrect result, but she acknowledged that early versions of the test didn't make it clear that women had to be at least seven weeks' pregnant before taking it and that DNA from their husbands could contaminate the results.
Acu-Gen's website lists dozens of clinical studies that it says corroborate its approach, though none of them involved the specific DNA sequence that Acu-Gen says it uses in Baby Gender Mentor and none reported accuracy as high as 99.9%.
A woman who answered the company's phone said she was "not interested" in discussing the test's accuracy. Other calls and e-mails to Acu-Gen were not returned. In court filings, the company denied "any wrongdoing and any liability" in connection with incorrect test results.
Diana W. Bianchi, a medical geneticist at Tufts-New England Medical Center in Boston who worked on the 2004 NIH study, said that little or nothing is known about the companies' methods.
"There's no evidence that they've undergone any quality assessment," she said. "As best as I can tell, anybody can set up a virtual shingle and open for business."
Complaints about the companies and the lawsuit against Acu-Gen have prompted Bianchi and others to call for federal regulation of the industry.
Currently, the tests are not regulated by the Food and Drug Administration because they aren't used to diagnose a medical condition, said spokeswoman Karen Riley.
Gail Javitt, law and policy director of the Genetics and Public Policy Center at Johns Hopkins University, said that gender tests could be considered diagnostic because some diseases are sex-specific. Nearly all patients with Duchenne muscular dystrophy or the blood clotting disorder hemophilia, for instance, are males.
Bianchi added that there is more at stake than just lost money or disappointment.
"As a physician, I'm most concerned not that someone has painted the nursery the wrong color, but what are the medical consequences of someone taking this test?" she said. An incorrect result could lead to "unnecessary amniocentesis and other procedures that carry a risk of miscarriage."
