Weeks after suing for patent infringement, Brisbane, California-based transplant diagnostics firm CareDx Inc. has accused rival Natera Inc. in Delaware federal court of intentionally misrepresenting the accuracy of its competing kidney-transplant rejection test.

In a complaint filed Wednesday morning, attorneys for CareDx said Natera, which is based in San Carlos, California, was using a flawed study to launch a “false marketing campaign,” designed to deceive doctors, insurance companies and patients into believing that its technology was superior to CareDx’s.