Tuberculosis in Systemic Lupus Erythematosus in an Endemic Area and the Role of Isoniazid Prophylaxis During Corticosteroid Therapy

Objective: The efficacy of isoniazid (INAH) prophylaxis against tuberculosis (TB) in patients taking corticosteroid remains controversial. Hong Kong is an endemic area for TB, with an annual risk of 0.11/100 in the general population. Patients with systemic lupus erythematosus (SLE) have an increased susceptibility to TB because of their intrinsic immunocompromised state and the use of corticosteroid therapy. We examined the usefulness of INAH in the prevention of recurrences of TB in patients with SLE receiving high dose corticosteroid therapy.

Methods: Medical records of a cohort of patients with SLE were reviewed. Patients with a history of TB who had previously been adequately treated were retrospectively examined for subsequent recurrence of TB. A comparison was performed based on the use of INAH at the discretion of the attending physician in some patients (INAH group) but not others (non-INAH group) during lupus exacerbation that required the use of prednisolone >/= 15 mg/day or equivalent.

Results: A total of 91 episodes of TB from 76 individuals in a cohort of 652 SLE patients with a duration of followup of 13.9 +/- 7.5 years were identified (prevalence of 1.06/100 patient-years). 43 episodes were given INAH while 48 were not. There were 18 recurrences of TB (recurrence rate of 1.66/100 patient-years). Recurrence rates in the INAH and non-INAH groups were 1.59 and 1.74 per 100 patient-years (p = 0.72). However, patients in the INAH group had more lupus exacerbations. Further, extrapulmonary TB was also found to have a higher recurrence rate than pulmonary TB. A case-controlled analysis was thus performed (n = 46) matching patients for the number of lupus exacerbations, cumulative doses of prednisolone, and initial site of TB. There was no difference in the recurrence rates of TB between the matched INAH (0.55/100 patient-years) and non-INAH (1.100 patient-years) groups (p = 0.66).

Conclusion: Patients with SLE have a higher prevalence of TB infection than the general population. They are at risk of TB recurrence when given immunosuppressive doses of corticosteroid.