Medical Confusion

A man goes to his physician to pick up his sick wife's results. The nurse on reception asks him the family name to which he replies 'Smith'.

'Mr Smith, we have so many of them that we can't find them. We've narrowed them down to two. Either she came in for an AIDS test or an ALZHEIMERS' test.'

'What shall I do?' exclaimed the concerned husband.

'Well I suggest you take your wife into town and leave her there. If she finds her own way home DON'T fuck her.'