The screening procedure itself may be inconvenient and have direct or indirect costs for the individual, which may vary with both the risk group and the screening approach. Harm associated with the results of screening include the unintended negative effects of a correct diagnosis (such as stigmatization or discrimination) and the harm caused by a false-positive or a false-negative screening test or diagnosis. Particular attention should be paid to harm to groups such as migrants, who may risk deportation if TB is diagnosed or presumed, and employees who lack legal protection against dismissal if they are diagnosed with TB. These risks should be identified, actively addressed and mitigated by the screening programme (see 2.2.6). The risk that screening leads to costs for the person being tested should also be reduced as much as possible, by ensuring that screening and potential further diagnostic testing and TB treatment is covered by insurance or the public health system.
The risk of a false-positive screen or a false-positive diagnosis depends on the prevalence of TB in the screened group and on the screening and diagnostic algorithm used. The harm due to a false-positive screening test result includes stress, anxiety and further diagnostic workup. Harm due to false-positive diagnostic test result includes unnecessary treatment and events. Screening of groups with a low TB prevalence can result in a large proportion of false-positive results. Therefore, as a general rule, screening of low-risk groups should be avoided. The importance of choosing an appropriate screening and diagnostic algorithm to minimize the number of false-positive outcomes is further discussed in 2.5 and in Chapter 3.
Potential harm is often due to inappropriate implementation. Contextual considerations are therefore important to ensure that screening is well designed and implemented and that both the potential benefits and harm are considered throughout the screening and diagnostic pathway (25).