Only in very rare circumstances and with certain forms of cancer present. The most common cause of seemingly changed blood types is the antigen sensitivity of the chemicals used to test the blood. Drugs or other factors about your blood may cause an erroneous readings. Operator error or poor lighting can result in an incorrect interpretation of the test results.
The Complete Blood Type Encyclopedia is the essential desk reference for Dr. D'Adamo's work. This is the first book to draw on the thousands of medical studies proving the connection between blood type and disease.