Stop TB Department
World Health Organization
Postal Address:Avenue Appia, CH-1211 Geneva 27, Switzerland
Telephone: (+44) 22 791 1028
Fax: (1-514) 22 791 1589
The tuberculosis (TB) detection rate is the percentage of estimated new infectious tuberculosis cases detected under the internationally recommended tuberculosis control strategy directly observed treatment shortcourse (DOTS).
TB is an infectious bacterial disease caused by Mycobacterium tuberculosis, which most commonly affects the lungs. It is transmitted from person to person via droplets from the throat and lungs of people with the active respiratory disease. In healthy people, infection with Mycobacterium tuberculosis often causes no symptoms, since the person's immune system acts to “wall off” the bacteria. The symptoms of active TB of the lung are coughing, sometimes with sputum or blood, chest pains, weakness, weight loss, fever and night sweats. Tuberculosis is treatable with a six-month course of antibiotics.
The term “case detection”, as used here, means that TB is diagnosed in a patient and is reported within the national surveillance system, and then to WHO. Smear-positive is defined as a case of TB where Mycobacterium tuberculosis bacilli are visible in the patient's sputum when examined under the microscope.
A new case of TB is defined as a patient who has never received treatment for TB, or who has taken anti-TB drugs for less than 1 month.
DOTS is the internationally recommended approach to TB control, which forms the core of the Stop TB Strategy (WHO, 2006b). The five components of DOTS are:
Estimates of incidence [please see incidence indicator] are based on a consultative and analytical process in WHO and are published annually (see reference 5).
The DOTS detection rate for new smear-positive cases is calculated by dividing the number of new smear-positive cases treated in DOTS programmes and notified to WHO divided by the estimated number of incident smear-positive cases for the same year, expressed as a percentage.
Estimates of incidence (for additional details, please refer to the TB incidence indicator metadata) are based on a consultative and analytical process lead by the WHO and are published annually.
For more information please see the following:
Global TB database: www.who.int/tb/country/global_tb_database
The upper bound and lower bound values are the 95% confidence intervals of mid-point (best) estimates of TB detection rate under DOTS.
Sputum smear-positive cases are the focus of this indicator because they are the principal sources of infection to others, because sputum smear microscopy is a highly specific (if somewhat insensitive) method of diagnosis, and because patients with smear-positive disease typically suffer higher rates of morbidity and mortality than smear-negative patients. However, national TB control programmes should aim to provide treatment to all patients, as set out in the Stop TB Strategy.
In principle, there is no discrepancy between global and national figures as national data are not modified.
The number of new smear-positive cases detected by DOTS programmes is collected as part of the routine surveillance (recording and reporting) that is an essential component of DOTS. Quarterly reports of the number of TB cases registered are compiled and sent (either directly or via intermediate levels) to the central office of the national TB control programme. Annual case notifications (and other data on programme performance) are collected by WHO via an annual data collection form, distributed to national TB control programmes through WHO regional and country offices.
A standardized data collection form is distributed to all countries on an annual basis. Estimates are made using these data as well as country-specific analyses of TB epidemiology based on the published literature and consultation with national and international experts.
The TB case notifications reported by countries follow the WHO recommendations on case definitions and recording and reporting, therefore, they are internationally comparable and there is no need for any adjustment.
No adjustments are made for missing values. DOTS detection rate data are available only for countries that implement the DOTS strategy and report case notifications to WHO.
Data on case notifications were reported to WHO from 202 countries or territories (see reference 5; annex 3).
Data on the numerator of this indicator (i.e. number of new smear-positive TB cases) were reported from 202 countries or territories for 2006. The data on denominator of this indicator are available for 212 countries or territories (see reference 5; Annex 3 in the “Method of Computation” section).
Data are produced annually.
Regional and global estimates are produced by aggregating national estimates, e.g. to calculate the global case detection rate of new smear-positive cases for a given year, the sum of number of new smear-positive cases reported by DOTS programmes of individual countries is divided by the sum of estimate of new smear-positive TB cases for the same countries and year multiplied by 100.
Estimates are published annually, in March, are available in WHO’s Global TB Database at http://www.who.int/tb/country/global_tb_database/en/.