I've been really concerned about my friend who's been having blood mixed with his morning sputum for the past three months. Since November, he's noticed a little blood in his saliva even during the day. He's had all sorts of tests done, like endoscopy, bronchoscopy, and blood tests, but everything's coming back normal. What other tests should he consider to get to the bottom of this, and which specialist should he see for a proper diagnosis? Also, could you recommend any good doctors in Coimbatore he could consult with?