AEGiS-14IAC: Impact of HIV on prevalent (active) TB disease in South African gold miners: implications for duration of infectivity, case-finding and TB transmission.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

Impact of HIV on prevalent (active) TB disease in South African gold miners: implications for duration of infectivity, case-finding and TB transmission.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. MoOrC1099)

Charalambous S, Moloi VM, Grant AD, Seabi O, Mangenene N, Rankhakile MK, Churchyard GJ, Corbett EL
Aurum Health Research, Welkom, South Africa

BACKGROUND: Factors influencing the prevalence of untreated TB disease, a major determinant of TB transmission rates, are poorly understood.

METHODS: Mineworkers attending annual fitness examination were tested for HIV with consent and screened for TB using a questionnaire, mini x-ray and microscopy and culture of 2 sputum specimens. Any abnormal findings were investigated further with examination, repeat radiograph, and 3 more sputum specimens. Case-definitions were applied to prevalent cases, and to incident TB cases from the same cohort in the year preceding. Mean duration of TB before diagnosis was calculated from the prevalence to incidence ratio.

RESULTS: Of 1978 participants, 580(29%) were HIV-infected. Prevalent TB disease meeting case-definitions was diagnosed in 2.8% (95%CI 2.1-3.6%), bacteriologically confirmed in 87% of cases. Age>40 yrs was a significant risk factor for prevalent TB (odds ratio [OR] 2.61, CI 1.37-4.98), but HIV infection was not (3.4% vs 2.5% for HIV+ve and HIV-ve respectively, OR 1.39, CI 0.80-2.43). TB incidence was 2.6 (CI 2.04-3.51)/100py (person-years), and was significantly HIV-associated (rates 5.9 and 1.4/100py respectively: incidence rate ratio (IRR) 4.40, CI 2.5-7.6). Other significant risk factors for incident TB were silicosis (p for trend <0.001) and age>40y (IRR 2.16,CI 1.15-4.05). The mean duration of TB before diagnosis was significantly shorter in HIV+ve than HIV-ve miners (means 0.58 yrs±0.32 and 1.8 yrs±1.00 respectively, p<0.023)

CONCLUSION: Although strongly associated with incident TB, neither HIV nor silicosis were significantly associated with prevalent TB, reflecting more rapid diagnosis in compromised hosts. This has major implications for case-finding and TB control. Even in high HIV prevalence areas, HIV-negative TB should not be underestimated, as it may contribute disproportionately to transmission owing to long duration of disease activity before diagnosis.

Keywords: AEGIS, Gold, HIV Infections, Mining, HIV Seropositivity, Incidence, Prevalence, Risk Factors, Silicosis, Vitamins, Dietary Supplements, Odds Ratio, transmission, pathogenicity

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