The Impact of HIV on Transmission of Tuberculosis in Ugandan Households

ABSTRACT

To examine the effect of HIV infection old infectiousness of TB. Design: Cross-sectional prevalence study of household contacts to smear positive TB patients. Methods: HIV-infected and non-infected index TB cases with sputum smear positive TB; were enrolled from a major TB clinic at Mulago Hospital in Kampala; Uganda. All full-time household contacts of the index cases were evaluated by medical history and physical examination; Mantoux purified protein derivative (PPD) skin tests; chest x-ray; BCG vaccination status; HIV test (in consenting subjects); TB symptoms and demographic and household environment. a contact with signs and/or symptoms of TB underwent a complete work-up for active TB. The main outcome measures were PPD positively and active TB. APPD skin-test readingor=5mm was considered positive. Results: 699 contacts of 170 index TB cases were included in this analysis. 319 (46) were contacts of 82 HIV+index TB cases. No significant differences were noted in the proportion of PPD positively; between contacts of HIV-infected and those pf the HIV-non-infected index cases [79versus 79; P=0.984]. Risk factors for PPD-positivity in contacts were AFB smear grade of the index case [Odds Ratio (OR) = 1.7; 95CI 1.16-2.37]; cavitary disease in the index case [OR=5.9; 95CI 2.53-14.0]; age of the contact [OR = 1.1; 95CI 1.05-1.10]; and household size [OR=0.9;95CI0.85-0.96]. Risk factors for active TB in contacts were cavitary disease in the index case [OR = 2.0;95CI 1.07-3.58]; age of the contact [OR = 1.1; 95CI0.89-0.96]; HIV status of the contact [OR=5.9;95CI1.69-21.9]; and sharing of bed or bedroom with the index case [OR=2.5; 95CI 1.54-3.92]. Conclusion: Transmission of M. tuberculosis within households was comparable among HIV-infected and non-infected index TB cases. However; transmission differed depending on whether the index case had cavitary disease; the sputum AFB smear; household sixe and age of the contact. HIV-infected contacts; children and intimate contacts of the index cases were at increased risk of having active TB at the time of household evaluation