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None of the screens investigated reached the target product profile of 90% minimum sensitivity in these high-risk subpopulations of children, although CXRs came the closest. Concerns were noted about the risk of incorporation bias when using a composite reference standard in this group, thus potentially inflating the estimates of accuracy observed.
The evidence reviewed about the performance of symptom screening (any one of current cough, fever, poor weight gain or close contact with someone with TB) included 2 studies conducted in the outpatient setting with a total of 20 926 participants and including 20 3135 screens (see Web Annex B, Table 19, and Web Annex C, Table 10).
For the purpose of this guideline, systematic screening for TB disease is defined as the systematic identification of people at risk for TB disease, in a predetermined target group, by assessing using tests, examinations or other procedures that can be applied rapidly. The screening tests, examinations and other procedures should efficiently distinguish people with a high probability of having TB disease from those who are unlikely to have TB disease.
Due to the inherent lack of access to health care that defines the risk groups described in this recommendation, screening interventions would need to be conducted in and extended into the communities where members of these populations live and work in order to achieve effective reach and coverage.
The list of potential populations affected by structural risk factors included in this recommendation is not exhaustive, and this recommendation may apply to other groups with a high risk of TB and who have poor access to health care, including poor access to high-quality TB services.
There is limited evidence on the effectiveness of different screening intervals. The GDG suggests that the screening interval should be no longer than 12 months if possible, while an interval shorter than 12 months may be more beneficial. To the extent possible, TB screening should be combined with screening for other diseases and with health-promotion activities, as well as with efforts to improve working conditions (especially by reducing exposure to silica) and living conditions.
Exposure to silica dust and silicosis are among the strongest risk factors for TB, with a relative risk of 2.8–39 for silicosis, depending on the severity of the disease (30). Silicosis is common in miners (31, 32), which is a primary reason for the high incidence of TB among them, and this is often compounded by a high prevalence of HIV. TB patients with silicosis have an increased risk of death (RR: 3.0; 95% CI: 1.4–6.3) (33).
Since the publication of the first WHO guidelines on systematic screening for TB in 2013 (5), there have been numerous studies, including reviews, randomized controlled trials, observational studies, modelling and cost–effectiveness research, evaluating the real or potential impacts of screening interventions on both individual-level and community-level outcomes related to TB. There have also been numerous prevalence surveys since 2013, which have shed new light on the magnitude of the burden of TB in several key countries.
This guideline is intended for personnel working in national TB programmes, national HIV/AIDS programmes or their equivalents, and other relevant national health programmes in ministries of health; other relevant ministries working in public health and screening; and for other health policymakers, clinicians and public health practitioners working on TB, HIV and infectious diseases in the public and private sectors. The recommendations provided here must be adapted to local settings. An accompanying operational handbook, WHO operational handbook on tuberculosis.
The specific objectives of the guideline update are:
1. to support Member States in implementing effective TB screening interventions by providing updated information about the expected impact of TB screening on patient-important outcomes and the epidemiology of TB, the expected yield of screening interventions and the expected performance of different screening tools and algorithms;
The evaluations reviewed by the GDG demonstrated substantial variation in the diagnostic accuracy (sensitivity and specificity) of CAD programmes across settings, even when using the same technology set to the same threshold. Thus, it will be essential to calibrate the threshold to be used for any given software for each setting and population in which it will be used in order to ensure that the accuracy, predictive values, overall yield and requirements for further diagnostic testing are as expected.