What could possibly go wrong:
The phone rings and the lady of the house answers, "Hello?"
"Mrs. Sanders, please."
"Speaking."
"Mrs. Sanders, this is Dr. Jones at St. Agnes Laboratory. When your husband's doctor sent his biopsy to the lab last week, a biopsy from another Mr. Sanders arrived as well. We are now uncertain which one belongs to your husband. Frankly, either way the results are not too good."

"What do you mean?" Mrs. Sanders asks nervously.

"Well, one of the specimens tested positive for Alzheimer's and the other one tested positive for HIV. We can't tell which is which."

"That's dreadful! Can you do the test again?" questioned Mrs. Sanders.

"Normally we can, but our health care system will only pay for these expensive tests just one time."

"Well, what am I supposed to do now?"

"The folks at the testing facility recommend that you drop your husband off somewhere in the middle of town. If he finds his way home, don't sleep with him."