Subclinical tuberculosis among adults with HIV: clinical features and outcomes in a South African cohort

BACKGROUND: Subclinical tuberculosis is an asymptomatic disease phase with important relevance to persons living with HIV. We describe the prevalence, clinical characteristics, and risk of mortality for HIV-infected adults with subclinical tuberculosis. METHODS: Untreated adults with HIV presenting for outpatient care in Durban, South Africa were screened for tuberculosis-related symptoms and had sputum tested by acid-fast bacilli smear and tuberculosis culture. Active tuberculosis and subclinical tuberculosis were defined as having any tuberculosis symptom or no tuberculosis symptoms with culture-positive sputum. We evaluated the association between tuberculosis disease category and 12-month survival using Cox regression, adjusting for age, sex, and CD4 count. RESULTS: Among 654 participants, 96 were diagnosed with active tuberculosis disease and 28 with subclinical disease. The median CD4 count was 68 (interquartile range 39–161) cells/mm(3) in patients with active tuberculosis, 136 (72–312) cells/mm(3) in patients with subclinical disease, and 249 (125–394) cells/mm(3) in those without tuberculosis disease (P < 0.001). The proportion of smear positive cases did not differ significantly between the subclinical (29%) and active tuberculosis groups (14%, P 0.08). Risk of mortality was not increased in individuals with subclinical tuberculosis relative to no tuberculosis (adjusted hazard ratio 0.84, 95% confidence interval 0.26–2.73). CONCLUSIONS: Nearly one-quarter of tuberculosis cases among HIV-infected adults were subclinical, which was characterized by an intermediate degree of immunosuppression. Although there was no significant difference in survival, anti-tuberculous treatment of subclinical cases was common. TRIAL REGISTRATION: Prospectively registered on ClinicalTrials.gov, NCT01188941 (August 26, 2010).