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. Among those whose screening is positive, the diagnosis needs to be established by diagnostic evaluation, consisting of one or more diagnostic tests, and clinical assessment, which together have high accuracy.
Systematic screening for TB disease is predominantly provider initiated. It may be conducted among people who do not seek health care because they do not have or recognize symptoms, they do not perceive that they have a health problem that warrants medical attention, there are barriers to accessing care, or for other reasons. It may also target people seeking health care who do or do not have symptoms or signs compatible with TB and who may not be identified by passive case-finding as possibly having TB. People seeking care who may be eligible for TB screening include people with medical conditions that constitute risk factors for TB (such as people living with HIV or diabetes mellitus) who may be seeking care for reasons other than symptoms compatible with TB.
There are two primary objectives of screening for TB disease: the first objective is to ensure that TB disease is detected early and treatment is initiated promptly, with the ultimate aim of reducing the risk of poor treatment outcomes, health sequelae and the adverse social and economic consequences of TB; the second objective is to reduce the community-level prevalence of TB disease, thus reducing transmission of Mycobacterium tuberculosis and averting future incident TB. Beyond TB disease, screening can also identify individuals who are eligible for and would benefit from TB preventive treatment (TPT) once TB disease is ruled out, thus further averting future incident TB.
Arising from these two primary objectives, there are two primary levels at which screening can augment standard TB care practices: that of the individual and the community. For individuals with TB disease, screening interventions can speed up and improve the probability of receiving a diagnosis and initiating treatment by bypassing many of the barriers to diagnosis and care that people suffering from TB disease can face, including (6):
- lacking knowledge about the signs and symptoms of TB;
- not recognizing symptoms;
- being unable to seek care or lacking sufficient resources for care-seeking;
- lacking access to TB diagnostic and treatment services;
- seeking care from providers who lack sufficient knowledge of TB or in facilities where TB diagnosis and treatment services are not available or of sufficient quality.
Beyond improving individual health and welfare, screening interventions for infectious diseases such as TB also address the epidemiology of the disease at the community level. By identifying and treating a proportion of the pool of individuals with TB disease in a given community, screening for TB seeks to reduce the prevalence, transmission and future incidence of the disease, with the long-term goal of eliminating the disease from the population.
The recommendations in this document apply to screening interventions that are conducted for the purpose of directly benefitting the individuals being screened by improving TB case detection and care and, thereby, benefitting the larger community by reducing the population burden of TB.