Note: Unless otherwise specified, the definitions listed below apply to the terms as used in this handbook. They may have different meanings in other contexts.

Active case finding (ACF): is synonymous with systematic screening for TB disease, although it normally implies screening that is implemented outside of health facilities.

Adolescent: is a person aged 10–19 years.

Adult: is a person over 19 years of age.

Bacteriologically confirmed TB: is TB diagnosed in a biological specimen by smear microscopy, culture or a WHO-approved molecular test such as Xpert MTB/RIF®.

Child: is a person under 10 years of age.

Contact: is any individual who was exposed to a person with TB disease.

Contact investigation: is a systematic process for identifying previously undiagnosed people with TB disease and TB infection among the contacts of an index TB patient and/or other comparable settings where transmission occurs. Contact investigation consists of identification, clinical evaluation and/or testing and provision of appropriate anti-TB therapy (for people with confirmed TB) or TB preventive treatment (for those without TB disease).

Close contact: is a person who is not in the household but shared an enclosed space, such as at a social gathering, workplace or facility, for extended periods during the day with the index patient during the three months before commencement of the current TB treatment episode.

Differentiated HIV service delivery (DSD) models: is a person-centred approach to simplify the provision of HIV services across the cascade, in ways that both serve the needs of People with HIV better and reduce unnecessary burdens on the health system.

High TB transmission setting: is a setting with a high frequency of individuals with undetected or undiagnosed TB disease, or where infectious TB patients are present and there is a high risk of TB transmission. TB patients are most infectious when they are untreated or inadequately treated. Transmission will be increased by aerosol-generating procedures and by the presence of susceptible individuals.

Household contact: is a person who shared the same enclosed living space as the index patient for one or more nights or for frequent or extended daytime periods during the three months before the start of current treatment.

Index patient (index case) of TB: is the initially identified person of any age with new or recurrent TB in a specific household or other comparable setting in which others may have been exposed. An index patient is the person on whom a contact investigation is centered but is not necessarily the source.

Infant: is a child under one year (12 months) of age.

Latent tuberculosis infection (LTBI): is a state of persistent immune response to stimulation by M. tuberculosis antigens with no evidence of clinically manifest TB disease. There is no gold standard test for direct identification of M. tuberculosis infection in humans. Most infected people have no signs or symptoms of TB but are at risk for TB disease. Given that the main difference from active TB is the absence of disease and given that infection cannot always be considered latent, LTBI is sometimes referred to as just “TB infection”.

People who use drugs: are those who engage in the harmful or hazardous use of psychoactive substances, which could impact negatively on the user’s health, social life, resources and legal situation.

Programmatic management of TB preventive treatment (PMTPT): includes all coordinated activities by public and private health caregivers and the community aimed at scaling up TB preventive treatment to people who need it.

At-risk group: is any group of people in which the prevalence or incidence of TB is significantly higher than in the general population.

Systematic screening for TB disease: is a systematic identification of people with presumed TB disease, in a predetermined target group, using tests, examinations or other procedures that can be applied rapidly. Among those screened positive, the diagnosis needs to be established by one or several diagnostic tests and additional clinical assessments, which together have high accuracy.

TB preventive treatment (TPT): Treatment offered to individuals who are considered to be at risk of developing TB disease, in order to reduce that risk. Also referred to as treatment of TB infection or LTBI treatment.

Tuberculosis (TB): is the disease that occurs in someone infected with M. tuberculosis. It is characterized by signs or symptoms of TB disease, or both, and is distinct from TB infection, which occurs without signs or symptoms of TB. In this document, it is commonly referred to as “active” TB or TB “disease” to distinguish it from LTBI or TB infection.

Underweight: among adults this usually refers to a body mass index < 18.5 and among children < 10 years of age to a weight-for-age < –2 z-scores.

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