Although terms such as 'chemoprophylaxis' and 'preventive chemotherapy' have been used, 'treatment of latent TB' is recommended by the American Thoracic Society. Investigation of latent TB is mandatory prior to the initiation of TNF antagonist therapy. Notwithstanding the fact that monoclonal antibodies seem to present a higher risk for reactivation of latent TB than soluble TNF receptors, screening and treatment of latent TB is warranted for all TNF antagonists regardless of their different molecular structure. This recommendation is supported by an observational study of the Spanish register BIOBADASER. The rate of TB was reduced by 80% after implementation of the official recommendations for isoniazid therapy for 9 months in patients with either positive TST (or two-step TST), past history of untreated TB or chest radiograph suggestive of past TB.[4] Recommendations for the general population by the American Thoracic Society and the British Thoracic Society in 2000 underscore the relevance of performing targeted TST in patients at risk such as those with recent TB exposure or those receiving prolonged immunosuppressive therapies.[83,84] Special attention was paid to children because youth implies recent infection and an increased likelihood of developing disease. More recommendations and evidence-based guidelines for patients undergoing treatment with TNF antagonists are available in several countries.[4,57,85–88] These national guidelines establish recommendations on screening methods and test cutoffs, and interpretation for diagnosis of latent TB. The best therapy for latent TB and the time delay before starting TNF antagonist therapy are also included in these guidelines. However, recommendations have disagreements; the TBNET consensus is the only international document that provides evidence-based advice for the assessment of latent TB in these patients. Experts recommend treating latent TB in all patients with positive IGRA tests or TST. However, IGRA can give false-negative results in approximately 20% of TB patients,[68,89] therefore different screening tools for diagnosis of latent TB must also be considered. Most guidelines recognize a history of significant past exposure or abnormal chest x-rays (suggestive of past TB) as indication for treatment of latent TB in the absence of an immune response to M. tuberculosis.[4,85,87,90] In patients treated adequately in the past, treatment of latent TB is not recommended despite persistent specific immune responses. On the other hand, guidelines emphasize that in patients with a negative TST or IGRA result, treatment is required if there has been past exposure or documented prior untreated TB. When IGRA and TST tests yield discordant results, the TBNET consensus recommends a consideration of history of prior BCG vaccination. If BCG vaccination was performed, IGRA test result should prevail over the TST result. If the patient has never been vaccinated with BCG, positive IGRA or TST result should be considered as such (Figure 2). Different delay periods between TNF antagonist therapy and initiation of latent TB treatment have been proposed. Recommendations range from starting both treatments concurrently to waiting until 1 month after finishing latent TB treatment. Therapy recommended for the treatment of latent TB includes 9–12 months of isoniazid in monotherapy,[5] or combining 3 months of isoniazid and rifampicin.[90] UK and Swiss guidelines propose isoniazid for 6 months or rifampicin for 4 months to minimize hepatotoxicity.[8
So it sounds like a possibility. Ugh!
