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The aim of this study was to assess the rate of defaulting from treatment among tuberculosis patients diagnosed in the Netherlands in the period 1993±1997, whether risk groups for defaulting can be identified at the start of treatment and the trend of defaulting over time.The Netherlands Tuberculosis Register provided data on all patients diagnosed in the Netherlands during the period 1993±1997. Defaulting probabilities were determined using Kaplan-Meier survival analysis and risk factors were identified with Cox's proportional hazard analysis.Of 7,529 patients with reported treatment outcome, 718 (10%) defaulted or left the country within 1 yr after starting treatment. Defaulting probabilities were 9% (95% confidence interval (CI) 8±10%) among 5,256 patients in low-risk groups, 17% (95% CI 14±19%) among 1,437 asylum seekers and 29% (95% CI 24±34%) among 836 patients in other high-risk groups (other recent immigrants, illegal immigrants, the homeless, prisoners and nationals from Eastern Europe). Defaulting probabilities decreased over time from 12% in 1993 to 7% in 1997.Risk groups for defaulting can be recognized at the start of treatment. The decreasing defaulting probabilities were probably due in part to shortening treatment from 9 to 6 months and improved follow-up of asylum seekers. However, additional measures are needed to reduce defaulting among the homeless, recent immigrants, illegal immigrants and prisoners.

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Many infections cause lasting detectable immune responses, whose prevalence can be estimated from cross-sectional surveys. However, such surveys do not provide direct information on the incidence of infection. We address the issue of estimating age and time specific incidence from a series of prevalence surveys under the assumption that incidence changes exponentially with time, but make no assumption about the age specific incidence. We show that these assumptions lead to a proportional hazards model and estimate its parameters using semi-parametric maximum likelihood methods. The method is applied to tuberculin surveys in The Netherlands to explore age dependence of the risk of tuberculous infection in the presence of a strong secular decline in this risk.

In Vietnam the spread of HIV infection is thought to be limited. In 12 urban districts of Ho Chi Minh City representative samples of tuberculosis patients have undergone HIV testing since 1995. HIV prevalence increased steeply from 0.5% in 1995 to 4% in 2000, with a doubling time of approximately 21 months. This study highlights the need to intensify HIV/AIDS prevention and control in Vietnam.