Guess You are going through Jerry Varghese process. Well it's not mandatory to go through Gamca , but I believe JV has had a tie up with these clinics & they will tell you that this is a legal process. They ask you to go through tests only to be sure of your health conditions, in fact you can get that done anywhere.

Moreover Once you are in qatar, you will definitely have to go through Medical tests under Medical Supreme Council and your reports will be submitted to government for issuing of QID. What you are undergoing in Mumbai is just a formality that the consultants like JV do to proceed ahead.