Well, the first thing to do would be to perform the test yourself at home. You don't need a doctor to do that.

Get your husband to lie flat on his back and ask him where the pain is. Press down on the painful spot and then get him to raise both his legs at the same time using his stomach muscles. If his pain gets worse, then that is a positive test response. You can then go to the doctor and say you have a positive Carnett's test and what is he/she going to do about it.

They should at least do a diagnostic injection as described in some of the earlier posts here.
If they refuse to do anything, well, then it's time to find a new doctor, I guess.