Research data supporting a non-invasive prenatal screen for Down's syndrome were "mishandled" and cannot be relied on, according to the biotechnology company that has been developing the test.

On 29 April Harry Stylli, chief executive of Sequenom in San Diego, California, said that four employees suspected of mishandling data had been suspended. An independent committee is investigating the matter. Investors have since filed several class-action lawsuits against the company.

Sequenom's tests rely on examining minute amounts of fetal DNA or RNA circulating in maternal blood. The hope is to provide an alternative to more invasive methods such as amniocentesis, which carry a small risk of miscarriage. The company intends to complete a new clinical validation of its assays by the end of the year, but will not file for regulatory approval until two larger clinical trials are completed in 2010.