Investigator on the phone : Hi, I am calling from so and so department. We are doing a study on so and so cancer. Would you like to participate in it?
Potential participant: I don't have cancer
Investigator : Is your name so and so?
Potential participant: Yes
Investigator: Our records say you have been diagnosed with cancer 4 months ago
Potential participant : I don't have cancer
Investigator : We have your medical records and your scheduled appointments with oncologists. We are aware that you discussed treatment options with your oncologist.
Potential participant: I don't have cancer !
Investigator : We know you have cancer
Potential participant: It's not me, it's my twin brother. He looks like me.
Investigator : CLICK
Investigator to us : He has a twin of the same name. They are probably conjoined twins, joint from waist down I suppose.