Added value of interferon-gamma release assays in screening for tuberculous infection in the Netherlands.

BACKGROUND: Interferon-gamma release assays (IGRAs) are reported to be more specific for the diagnosis of latent tuberculous infection (LTBI) than the tuberculin skin test (TST). The two-step procedure, TST followed by an IGRA, is reported to be cost-effective in high-income countries, but it requires more financial resources. OBJECTIVE: To assess the added value of IGRA compared to TST alone in the Netherlands. METHODS: Test results and background data on persons tested with an IGRA were recorded by the Public Municipal Health Services in a web-based database. The number of persons diagnosed with LTBI using different screening algorithms was calculated. RESULTS: In those tested with an IGRA, at least 60% of persons who would have been diagnosed with LTBI based on TST alone had a negative IGRA. Among those with a TST reaction below the cut-off for the diagnosis of LTBI, 13% had a positive IGRA. For 41% of persons tested with an IGRA after TST, the IGRA influenced whether or not an LTBI diagnosis would be made. CONCLUSION: With the IGRA as reference standard, a high proportion of persons in low-prevalence settings are treated unnecessarily for LTBI if tested with TST alone, while a small proportion eligible for preventive treatment are missed. Incremental costs of the two-step strategy seem to be balanced by the improved targeting of preventive treatment.

Coverage and yield of tuberculosis contact investigations in the Netherlands.

SETTING: An increasing proportion of tuberculosis (TB) patients in low-incidence countries are immigrants. It is unclear whether contact investigations among immigrant patients are adequate. OBJECTIVE: To determine whether ethnicity of pulmonary TB patients was associated with coverage and yield of contact investigations in the Netherlands. DESIGN: Contact investigation results were extracted from records of patients reported in the nationwide surveillance register in 2006 and 2007. Prevalence odds ratios (PORs) with 95% confidence intervals (CIs) were calculated to determine the association between patient ethnicity and coverage of contact investigations and the yield of individuals with Mycobacterium tuberculosis infection or TB. RESULTS: Of the 1040 pulmonary TB patients reported, 642 (62%) were eligible for analysis. Compared to close contacts of Dutch patients, close contacts of immigrant patients were significantly less likely to be examined for TB (89% vs. 93%, POR 0.6, 95%CI 0.5-0.7) and infection (50% vs. 75%, POR 0.3, 95%CI 0.3-0.4), whereas the yield was significantly higher for disease (1.5% vs. 0.4%, POR 3.4, 95%CI 1.8-6.4) and infection (13% vs. 10%, POR 1.2, 95%CI 1.0-1.5). CONCLUSION: The effectiveness of contact investigations in the Netherlands can be optimised by expanding the investigation of contacts of immigrant patients.

Tuberculosis contact investigation in low prevalence countries: a European consensus.

Contact investigation to identify individuals with tuberculosis and latent infection with Mycobacterium tuberculosis is an important component of tuberculosis control in low tuberculosis incidence countries. This document provides evidence-based and best-practice policy recommendations for contact tracing among high- and medium-priority contacts in a variety of settings. It provides a basis for national guidelines on contact investigation and tuberculosis outbreak management, and should support countries and tuberculosis control managers in evaluating and revising national policies. A review of existing guidelines, a literature search, several meetings and consultation with experts were used to formulate and grade recommendations for action during contact investigation. Available tests to identify individuals with latent infection with M. tuberculosis are designed to identify immune response against mycobacterial antigens and have variable predictive value for the likelihood to develop active tuberculosis in different populations. Contact investigation should therefore be limited to situations with a clear likelihood of transmission or to those with a higher probability of developing active tuberculosis, for instance, young children and immunocompromised persons. A risk assessment-based approach is recommended, where the need to screen contacts is prioritised on the basis of the infectiousness of the index case, intensity of exposure and susceptibility of contacts.

[Estimation of the incidence of tuberculosis in The Netherlands in 2030]. / Projectie van het aantal tuberculosepatiënten in Nederland in 2030.

OBJECTIVE: To estimate the number of cases of tuberculosis (TB) in 2030 for the purpose of planning future TB control. DESIGN: Statistical modelling in 5-year intervals until 2030. METHOD: The number of Dutch TB cases infected by a Dutch source was estimated using a survival model. The number ofnon-Dutch patients was estimated by calculating the proportion of culture-positive TB patients among first-generation immigrants in 2005 and applying this proportion to the projected size of the non-Dutch population. It was assumed that each non-Dutch TB patient infected by a non-Dutch source would cause one infection in the population in The Netherlands. RESULTS: The estimated number of TB cases is expected to decrease to 877 in 2010. Only a limited decrease in the number of TB patients is expected after 2010 as the number of non-Dutch TB cases increases due to increased immigration. This increase negates the expected decrease in Dutch TB patients infected by a Dutch source. In 2030, non-Dutch TB cases will account for 85% of all TB cases. The proportion of non-Dutch TB cases is greater in the 4 largest cities, i.e. Amsterdam, Rotterdam, The Hague and Utrecht (89%) than in the rest of The Netherlands (76%). CONCLUSION: The decrease in TB incidence observed over the past several years may cease by 2010 due to an increase in non-Dutch TB patients as a result of increased immigration. However, the confidence intervals associated with these estimates were large. Future TB control efforts must be organised in a flexible way so that they can be adapted to changing epidemiological situations.