My son had negative PPD but suspicious chest x-ray before Humira. They suggested INH. Five years into Humira, he is fine. The worry is latent TB can be activated during therapy. The INH prevents this.
Here is the remicade recommendations, copied from website:
Regarding tuberculosis: The following treatment algorithm is an appropriate one to follow: PPD should be performed on all patients prior to starting Remicade. In those patients who have already started Remicade a PPD should also be performed but a negative tests may be due to immunosuppression and not a true negative. Clinical follow-up for TB is thus indicated and a chest X-ray should be performed. In patients starting or taking Enbrel, even though this drug has a much lower association with TB, high-risk patients for TB should also have a PPD. In patients with a negative PPD, Remicade can be started and clinical monitoring for TD instituted. In those patients with a positive PPD, a chest X-ray should be performed. If the chest X-ray is negative, then 9 months of 300 mg INH and 50 mgm of vitamin B6 should be given. Concomitant use of Remicade in this situation is appropriate. Observation for any infection is indicated.
If the PPD is positive and the chest X-ray shows apical disease typical of TB or calcified hilar nodes (Gohn complex), at least 3 months of INH and B6 are indicated prior to starting Remicade. Or, if active TB is clinically possible, a pulmonary or infectious disease consult is appropriate. Remember to follow liver function tests in patients started on INH especially those older than 50. If the PPD is positive but the patient has already had a course of INH in the past for a known positive PPD, Remicade can be started with the usual clinical observation for infection.