Evaluating the effectiveness of interventions for the prevention of tuberculosis in a low-incidence setting

The thesis presents studies into the effectiveness of specific tuberculosis (TB) control interventions in the Netherlands aimed at early case finding and prevention of TB. The first study showed screening of new immigrants upon entry met the criteria for risk group screening of more than 50 per 100,000 population. Abnormalities in the chest-X-ray without the presence of active TB was a powerful predictor of the development of TB during the following 2 years. In those with a normal chest X-ray , bi-annual follow-up screening met the criteria for risk group screening only for immigrants from countries with an estimated TB incidence of more than 200 per 100,000 population. The second study showed the added value of interferon gamma release assays (IGRA) for the diagnosis of latent TB infection (LTBI). When used to confirm the diagnosis of LTBI after a tuberculin skin reaction of 5 mm or more, IGRA reduced the number needed to treat to prevent a new TB patient with 60%. The third study showed Dutch TB control effectively detects and prevents TB among children. Improving coverage of BCG-vaccination and screening of immigrant children for LTBI will prevent further TB cases. The final studies describe the trends in target groups for screening, and independent risk factors for acceptance, completion and the occurrence of adverse events of preventive treatment on LTBI. Preventive treatment has the largest impact on TB incidence in the two years after LTBI diagnosis among TB contacts and children younger than 5 years.