Free COVID-19 Antibody TestingFree COVID-19 Antibody Test For Donating Blood, Platetets or Plasma. This testing may provide critical insight into whether donors may have possibly been exposed to this coronavirus. The Red Cross is committed to helping others in meaningful ways during this pandemic. An antibody test screens for antibodies in your blood. Antibodies are formed when fighting infection, like COVID-19. An antibody test assesses whether your immune systems has responded to the infection, not if the virus is currently present.