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

BackgroundSubclinical 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.MethodsUntreated 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.ResultsAmong 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).ConclusionsNearly 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 registrationProspectively registered on ClinicalTrials.gov, NCT01188941 (August 26, 2010).