Mantoux skin test reactivity among household contacts of hiv-infected and hiv un-infected patients with sputum smear positive TB in Dar Es Salaam, Tanzania

Abstract

To compare the prevalence of Tuberculosis (TB) infection as demonstrated by a positive Mantoux skin test (MST) among household contacts of sputum smear positive (SSP) HIV infected and un-infected TB patients. A cross-sectional study of household contacts of patients with TB (index cases) attending Muhimbili National Hospital, and TB clinics of Infectious Disease Control Centre and Municipal hospitals in Dar es Salaam. Index cases with SSP-TB and aged > or =18 years had their HIV serostatus determined by ELISA. Contacts of index cases aged > or =1 year received intradermal protein-purified derivative (Mantoux test) and results were read after 72 hours. Infected contacts (MST-positive) received medical evaluation to exclude TB disease. The overall prevalence of TB infection among contacts of HIV infected and un-infected index cases were 61.6% and 62.5% respectively, (OR 1.04 [95% CI 0.61-1.76], p=0.887). Factors associated with an increased risk of TB infection among contacts of both HIV infected and un-infected index cases were: older age of contacts (> or =25 years), duration of living with index case prior to TB diagnosis of > or =1 year, and sharing a room with index case. Infectiousness to their contacts was higher among female compared to male index cases. The proportion of household contacts of SSP PTB index cases with a positive MST was high and uninfluenced by the HIV serostatus of the index case. Efforts towards contact tracing and screening for TB among close contacts of SSP PTB patients should be enhanced.