Silly, totally un-PC gag, but it made me laugh
"Mrs. Ward, please."
"Mrs. Ward, this is Doctor Jones at the Medical Testing Laboratory. When your doctor sent your husband's biopsy to the lab yesterday, a biopsy from another Mr. Ward arrived as well, and we're now uncertain which one is your husband's. Frankly the results are either bad or terrible."
"What do you mean?" Mrs. Ward asks nervously.
"Well, one of the specimens tested positive for Alzheimer's,and the other one tested positive for AIDS. We can't tell which specimen is your husband's."
"That's dreadful! Can't you do the test again?" questioned Mrs. Ward.
"Normally we can, but Medicare will only pay for these expensive tests one time."
"Well, what am I supposed to do now?"
"The people at Medicare recommend that you drop your husband off somewhere in the middle of town. If he finds his way home, don't sleep with him."
With all due apologies to sufferers of both AIDS and Alzheimer's - who, if they are anything like the cancer warriors I know - will see the funny side of this just as we cancer warriors do with equivalent gags.