TB KaSPar
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Before implementation of a programme, its cost–effectiveness, or cost-benefit – in which costs and benefits are compared in monetary terms – can be modelled from estimates of the predicted number of additional true-positive TB patients detected, the reduction in morbidity, the reduction in the time that a person remains infectious and reductions in transmission, incidence and mortality.
The potential of screening to affect transmission is theoretically highest in congregate settings, such as prisons or overcrowded urban slums, where there is a high rate of transmission and where there is also substantial in-migration and out-migration. In a study in Viet Nam, 3 years of community-wide screening decreased the prevalence of pulmonary TB (26). In principle, the larger the total yield of screening, the larger the potential impact on TB transmission in the community.
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.
The benefits include the health, social and economic benefits of early diagnosis and treatment. In principle, the potential benefits are greater for persons who are at highest risk of delayed or missed diagnosis because they meet barriers in obtaining health care (for example, people living in poor communities or remote areas) and especially those at highest risk of unfavourable treatment outcomes when diagnosis is delayed (for example, because their immune system is compromised, such as people living with HIV and children).
The primary goal of TB screening is to reach people who are not reached by the patient-initiated pathway and to detect TB disease early, thereby improving outcomes for individuals and reducing transmission and incidence at population level.
Secondary goals of TB screening are to:
Discrimination based on gender, sexuality, ethnicity or caste or against populations such as sex workers and people who use or inject drugs, can severely limit access to treatment, which may be reinforced by the lack of a framework for protecting human rights. The existing frameworks for protecting human rights and the extent to which they are enforced must be reviewed before systematic screening is implemented.
Before screening is started, it is essential to ensure that people with diagnosed TB have access to affordable, high-quality TB care. This may not be the case for certain vulnerable groups, such as migrants, refugees and homeless people, who may lack identity papers or health insurance. Inclusion criteria for screening, coverage of health insurance (where applicable) and access to health services should be assessed. The system should ensure that people do not pay out of pocket for screening and do not suffer financial hardship as a result of screening.
High-quality services for TB diagnosis, treatment and management and support services for patients should be in place before or scaled up at the same time as systematic screening for TB disease.
The acceptability and feasibility of screening for those who will be screened and those who will provide screening should be assessed. Whether screening is accepted depends on how the programme is designed and implemented. Acceptability is therefore difficult to predict from evidence for other sites or for other subgroups. The acceptability of screening may be assessed in advance by organizing focus groups of target populations, preferably with a risk profile and an age and sex distribution that matches that of the populations at highest risk.
The provider-initiated screening pathway to TB diagnosis entails systematic identification of people with possible TB disease in a predetermined target group with tests, examinations or other procedures that can be applied rapidly. In those with a positive screening test result, the diagnosis must be established by one or several diagnostic tests and additional clinical assessments, which together are highly accurate.