Pip Review

Hi I sent off my review forms after they was requested by the dwp as the end date was going to be April this year gone. They received the forms back in September last year. I did a phone call Assesment two weeks ago explaining how my health has further deteriorated etc. My question is if the dwp requested a review will I be entitled to any back pay if I do get an increase. If so when will it be backdated to. Thank you in advance.