Objective: To determine if low-risk elderly patients with rheumatoid arthritis (RA) who screen positive for latent tuberculosis (TB) infection prior to anti–tumor necrosis factor (anti-TNF) therapy should be given isoniazid (INH).
Methods: A Markov model was developed. The base case was a patient age 65 years with RA starting anti-TNF therapy with a positive tuberculin skin test (TST) finding of 5–9 mm, who was born in a country with low TB prevalence and had no other TB risk factors. The decision was 9 months of INH or not. The primary outcome was quality-adjusted life expectancy. Multiple sensitivity analyses were performed.
Results: No prophylaxis was favored, with a gain of 1.1 quality-adjusted life days, but the decision was sensitive to several variables. Prophylaxis was favored for patients ages <61 years, if the relative risk (RR) of TB reactivation with RA alone was >2.5, if the RR with anti-TNF therapy was >5.8, or if the utility associated with INH therapy was >0.98. Prophylaxis was also preferred for patients with a TST result >10 mm and for patients from higher risk countries. If 6 months of INH or 4 months of rifampin were used, prophylaxis was preferred, providing that therapy reduced the risk of TB reactivation by >47% and >27%, respectively.
Conclusion: Withholding prophylaxis prior to anti-TNF therapy may be reasonable for low-risk elderly RA patients with a TST finding of 5–9 mm, although the decision is sensitive to patient preferences. For patients age <61 years from a higher risk country, or with a TST finding >10 mm, prophylaxis is preferred.