Relapse more common than reinfection in recurrent tuberculosis 1-2 years post treatment in urban Uganda

To determine the proportion of recurrent tuberculosis (TB) due to relapse with the patient's initial strain or reinfection with a new strain of Mycobacterium tuberculosis 1-2 years after anti-tuberculosis treatment in Uganda, a sub-Saharan TB-endemic country.

Records of patients with culture-confirmed TB who completed treatment at an urban Ugandan clinic were reviewed. Restriction fragment length polymorphism (RFLP) patterns were used to determine relapse or reinfection. Associations between human immunodeficiency virus (HIV) positivity and type of TB recurrence were determined.

Of 1701 patients cured of their initial TB episode with a median follow-up of 1.24 years, 171 (10%) had TB recurrence (8.4 per 100 person-years). Rate and risk factors for recurrence were similar to other studies from sub-Saharan Africa. Insertion sequence (IS) 6110-based RFLP of paired isolates from 98 recurrences identified 80 relapses and 18 reinfections. Relapses among HIV-positive and -negative patients were respectively 79% and 85% of recurrences.

Relapse was more common and presented earlier than reinfection in both HIV-positive and -negative TB patients 1-2 years after completing treatment. These findings impact both the choice of retreatment drug regimen, as relapsing patients are at higher risk for acquired drug resistance, and clinical trials of new TB regimens with relapse as clinical endpoint.