I was aware of this. What exists on Chennai site is a "Case Search Functionality". What results out of this search is a case number, category and interview date and time.
But what the appointment letter contains is above plus names of all candidates who are required to undergo the interview.
What I am not sure about is whether a hospital/ doctor would accept a printout displaying case number, category and interview date + time ( & no names) to conduct a medical check up.
I had asked a similar question @ Breach Candy in Mumbai and they said they would like to see an appointment letter which states person's names including all other ancillary details! This may not be true at Chennai as the email reads.
So in your case what I would suggest is take a printout of Chennai's email plus printout of case details from Chennai web site and attend medicals and it should not be a problem.
But this scenario will not work in Bombay, especially Breach Candy (not sure about Lilavati/ Hinduja) since hospitals / doctor do not know whom the case number is associated with if they do not see an appointment letter.