From a global perspective, tuberculosis is a common disease. It is often associated with poverty-related living conditions and more common in low-income countries. In Germany, the disease is rare, with 4.7 new cases per 100,000 inhabitants. Most of those suffering from tuberculosis in Germany are born in countries with a high incidence of the disease. Some countries therefore screen newly arriving people for possible tuberculosis. A team of international scientists led by Professor Dr Kayvan Bozorgmehr from Bielefeld has investigated whether a single screening after arrival is sufficient or whether there should be follow-up screenings and how these should be designed. The study was published in the medical journal PlosMedicine.
An infection with tuberculosis can be asymptomatic and it may take years for the disease to develop. Globally, it is a common disease, and many high-income countries screen newly arriving people in order to detect tuberculosis disease at an early stage.
© Britta Kirst/MAKI Photo Lab
‘International studies have shown that tuberculosis can remain undetected despite upon-entry screening. Often, the disease develops within the first two to four years after arrival. This may partially be associated with unfavourable living conditions,’ explains Bozorgmehr. This is why some countries perform additional follow-up screenings—that is, they repeat screening measures for persons who have not been diagnosed with tuberculosis, but may be considered to be at risk of developing it in the future.
The effectiveness of such follow-up screenings has been known for years. Until now, however, there has been no research on how to design programmes, and how their design may impact on their effectiveness. ‘We examined the characteristics of different programmes worldwide and compared them in terms of participation rates and yield,’ says Dr Katharina Wahedi, lead author of the study: ‘We particularly examined whether mandatory programmes have advantages over voluntary ones, and what added value multiple follow-up examinations have compared to a single follow up.’
Mandatory programmes do not deliver better results
‘Our study shows that mandatory programmes for post-entry tuberculosis screening can lead to a higher participation rate in some cases, but do not deliver better results in terms of case finding,’ is how Bozorgmehr summarizes the central findings of the study. The epidemiologist judges voluntary programmes to be not only just as effective but also ethically and legally more justifiable, because the persons to be screened are considered healthy at the time of follow up. Moreover, according to Bozorgmehr, multiple follow-up screenings do not seem to achieve significantly better yields than just a single follow-up screening.
Challenges when comparing international studies
The researchers systematically searched the scientific literature to identify studies on follow-up screening programmes. ‘We found 23 studies that met our inclusion criteria,’ says Wahedi. However, the individual programmes in each country applied very different concepts and implementations of follow-up screening. This helps when it comes to understanding which strategies work better and what might be an effective structure for a follow-up programme, Wahedi explains. ‘However, studies varied widely in terms of, for example, who was classified as at-risk. Such inconsistent criteria make studies difficult to compare.’
Application in practice
In Germany, proactive case finding for tuberculosis is limited exclusively to persons living in community housing. Such persons include refugees, asylum seekers, and the homeless. However, individual risk factors are not taken into account, screening is indiscriminate and mandatory, and it is one off. ‘A one-off screening for tuberculosis may not be enough,’ says Kayvan Bozorgmehr. ‘It detects only a small proportion of those infected. An infection is usually diagnosed only when more severe symptoms have already developed and it is also more advanced.’
To achieve earlier treatment and thus a better prognosis and lower treatment costs, the authors suggest that proactive case-finding strategies should be expanded. Bozorgmehr explains: ‘From a population health perspective, a voluntary follow-up, which is well integrated into the health system and is based on adequate information and consent, is an effective component of national TB control programmes. Up to now, there are no data showing that mandatory programmes achieve better yields than voluntary ones. In light of the ethical and legal consequences of mandatory medical screenings, strategies building on compulsory approaches are questionable.’ The study was funded by the Federal Ministry of Education and Research (BMBF).