2.1.1 Summary of the evidence and rationale

Systematic screening in the general population is conducted on the premise that it bears dual benefit: to the persons diagnosed with TB and to the community in which screening is conducted. Individuals found to have TB may benefit from less diagnostic delay, improved treatment outcomes, and lower costs and financial losses associated with the disease. It also benefits public health by reducing the population prevalence of TB, thereby reducing further transmission of TB.

There is limited direct evidence of individual benefit from improved treatment success or reduced mortality when TB screening is performed in the general population. There is some evidence that systematic screening helps reduce delay in TB diagnosis and that it detects patients at an earlier stage of their disease. Data also show that screening interventions result in a reduction in costs for patients who are detected through screening and, most critically, a reduction in the risk of catastrophic costs for patients detected through screening and their families. However, some data show that the proportion of people who do not start treatment is higher among those identified through screening than among those who present with illness.

With respect to the benefits of screening for the community, there is inconsistent evidence that systematic screening for TB improves detection and notification in the general population, with none coming from randomized trials. There is, however, evidence of an effect on TB prevalence and transmission. A trial in Viet Nam in a population with an estimated prevalence of 0.35% that used 3 years of annual door-to-door sputum collection and testing using the Xpert MTB/RIF assay showed that systematic screening reduced adult TB disease prevalence (13). An observational study in China conducted between 2013 and 2015 reported that three rounds of door-to-door symptom screening followed by CXR were associated with serial reductions in the absolute number of people with TB detected (14). In addition, two trials showed lower frequencies of TB infection among children in clusters where TB screening was done compared with others without the intervention (13, 15).

This is an updated recommendation: previously, systematic screening for TB disease in the general population was recommended in defined populations with extremely high levels of undetected TB, defined as a 1% prevalence or higher. Based on the updated evidence reviewed, the GDG concluded that the threshold of 1% recommended in the 2013 guidelines could be lowered, but considered that screening under programmatic conditions would not perform as well as was observed in the trial in Viet Nam and, therefore, proposed a 0.5% threshold to guide country implementation. Thus, the GDG recommended that general population screening may be considered in defined areas with a prevalence of undetected TB of 0.5% or more (see Web Annex B, Tables 1 and 2, and Web Annex C, Table 1).

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