Mantoux skin test reactivity among household contacts of hiv positive and hiv negative patients with sputum smear positive tuberculosis

Abstract

Background: Tuberculosis has been increasing in many parts of the world since the late 1980s. In Africa much of this increase has been attributed to the HIV epidemic. The increased risk of tuberculosis in those infected by HIV is well known. It is likely that this increase will be accompanied by the onward transmission of Mycobacterium tuberculosis. The increased potential for HIV -associated TB cases to transmit M tuberculosis and to produce a secondary increase in TB morbidity is controversial. Objectives: To compare the prevalence of Tuberculosis infection as demonstrated by a positive Mantoux skin test (MST) reactivity among household contacts of sputum smear positive HIV positive and HIV negative Tuberculosis patients. Methodology: The study took place at the Muhimbili National Hospital, outpatient Tuberculosis clinics of Infectious Disease Control Centre (IDC), and the three Municipal hospitals in Oar es Salaam. Consenting male and female Index cases (both HIV positive and HIV negative) aged 18 and above with sputum smear positive tuberculosis were enrolled so as to obtain their respective household contacts aged 1 year and above. The contacts were injected intradermally with protein purified derivative (Mantoux test) and the results were read after 72 hours. Contacts found to be infected (mantoux skin test positive) were counseled for medical examination to exclude Tb disease. Results: The prevalence of Tb infection among household contacts of HIV positive and HIV negative index cases were 61.6% and 62.5% respectively, (OR 1.04 [95% CI 0.61 - 1.76], p=0.887). In order to minimize the effect of environmental Mycobacteria on the MST response, the analysis was restricted to household contacts aged 1 -14 years of the HIV positive and HIV negative index cases, again in this analysis the prevalence of Tb infection in this group did not differ, (OR 1.39 [95% CI 0.63 - 3.07], p=0.419). Factors associated with an increased risk of Tb infection in household contacts of both HIV positive and HIV negative index cases were older age of the contacts (25 years and more), long duration of living with the index case prior to Tb diagnosis (one year and more), and sharing a room with the index case. Among index cases, female gender was associated with a higher infectiousness to their contacts. Conclusion and Recommendation: The patients with Pulmonary Tuberculosis and HIV co-infection have the same likelihood of infectiousness to their contacts as those who are not HIV infected. Efforts towards contact tracing and screening for TB among close contacts of smear- positive pulmonary TB patients should be enhanced as this could have a positive impact on TB prevention and control.