One test two results

A man phones the Doctor’s surgery for the results of his wifes blood test she had the day before. The Doctor was very embarrassed and replies “Ah yes Mr jones,” “I have to apologise for a mixup.” Mr Jones “said oh what mixup?” “We have two sets of results accredited to your wife and we are not sure which one is the correct result  for your wife.”

Mr Jones then irritably said “So she needs to have yet another test you mean?” “Oh no need” said the Doctor, “You see, one test indicates HIV and the other indicates Dementia , there is no need to re-test as we can easily work out which one is applicable.” Mr Jones then asks “How can you tell without a test?” The doctor then stated “Just send your wife to the surgery to collect her results, and if she finds her way home, don’t fuck her!”