New methods for estimating the tuberculosis case detection rate in high-HIV prevalence countries: the example of Kenya

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Abstract
To develop new methods for estimating the sputum smear-positive tuberculosis case detection rate (CDR) in a country where infection with HIV is prevalent. We estimated the smear-positive tuberculosis CDR in HIV-negative and HIV-positive adults, and in all adults in Kenya. Data on time trends in tuberculosis case notification rates and on HIV infection prevalence in adults and in tuberculosis patients were used, along with data on tuberculosis control programme performance. In 2006, the estimated smear-positive tuberculosis CDR in HIV-negative adults was 79% (95% confidence interval, CI: 64–94) and in HIV-positive adults, 57% (95% CI: 26–88), giving a weighted mean of 68% (95% CI: 49–87). The separate estimate for all smear-positive tuberculosis cases was 72% (95% CI: 53–91), giving an overall average for the three estimates of 70% (95% CI: 58–82). As the tuberculosis CDR in 1996 was 57% (95% CI: 47–67), the estimated increase by 2006 was 13 percentage points (95% CI: 6–20), or 23%. This increase was accompanied by a more than doubling of the resources devoted to tuberculosis control in Kenya, including facilities and staff. Using three approaches to estimate the tuberculosis CDR in a country where HIV infection is prevalent, we showed that expansion of the tuberculosis control programme in Kenya led to an increase of 23% in the CDR between 1996 and 2006. While the methods developed here can be applied in other countries with a high prevalence of HIV infection, they rely on precise data on trends in such prevalence in the general population and among tuberculosis patients.