British researchers have developed a new blood test that can screen for the abnormal prion protein that is associated with mad cow disease, officially called Creutzfeldt-Jakob Disease. A test of 190 blood samples, resulted in a 70 percent accuracy rate. Since mad cow disease is also passed through blood transfusions, researchers hope the test could one day be used to identify contaminated blood to prevent further disease. They say, however, that in its current state, the test may not detect early stages of the disease and will need further testing before being implemented. Mad cow disease has killed 171 people and more than 4 million cattle worldwide.