This is a step that you can follow yourself, relatively easily. There are multiple sources of reviews online. They give you a fair idea of what clients are saying about the dermatologist and their opinions on how good they are. The drawback is the control on false information since most reviews are open source and there can be incorrect information, both good and bad.
A deeper look would involve seeing the responses of the dermatologist to the reviews. Do they respond regularly? Are the responses polite? Have they informed people when they see a fake bad review? Have they solicited false positive reviews?
There are telltale factors which let you know these things. You just need to look deep enough. A good example to help sort through an incorrect positive review is to see the forced insertion of a keyword ( a common word that people search for online) in the review.
Another method is to see if the reviewer has provided feedback for multiple specialists from the same field. It indicates that it could be a ‘professional’ reviewer who may seek benefits for showing someone in a good OR bad light.
Finding a false negative review is relatively easier since the clinic or specialist would have usually marked that out themselves. Our research into client feedbacks found that suspected false reviews also tend to be shorter and non-descriptive beyond the keyword, but that is very subjective.