It is inadvisable for people to waste their time or money on tests. There is no way to predict whether a particular person will develop the disease. It is possible to test for the ApoE4 gene, but such a test does not predict whether a particular person will develop Alzheimer's disease or not. It merely indicates that he or she is at greater risk. There are in fact people who have had the ApoE4 gene, lived well into old age and never developed Alzheimer's disease, just as there are people who did not have ApoE4, who did develop the disease. Therefore taking such a test carries the risk of unduly alarming or comforting somebody. Only in very rare families where Alzheimer's disease is a dominant genetic disorder unaffected relatives may take a predictive diagnostic test. The test must be preceded, accompanied and followed by comprehensive counselling.