Smear test question from a man/brother?

I have a couple of sisters in their 30s and I receive from the local doctor's place letters inviting them to go for smear test appointments. I know that because the letters arrive here. They never go, because they never do anything sexually - I just inform them that the letters have arrived. I suspect both of them are a little embarbaased about undressing in front of a female doctor - I just know what they are like; they would never do it. Can they ask for a male doctor and, if they do nothing in a sexual way, is the test necessary?