Tuberculosis detection rate under DOTS (percentage)

Rationale for use

The proportion of estimated new smear-positive cases of TB detected (diagnosed and then notified to WHO) by DOTS programmes provides an indication of the effectiveness of national TB programmes in finding and diagnosing people with TB.

Millennium Development Goal Indicator 24 (under Goal 6, Target 8) is the "proportion of tuberculosis cases detected and cured under DOTS". The Stop TB Partnership has endorsed the targets, linked to the Millennium Development Goals, to diagnose at least 70% of people with sputum smear-positive TB (i.e. under the DOTS strategy), and cure at least 85%, by 2005. These are targets set by the World Health Assembly of WHO.

In 2005, an estimated 60% of new smear-positive cases were treated under DOTS, ranging from 35% in the WHO European Region to 76% in the Western Pacific Region.

Definition

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. The case-detection rate is calculated as the number of new smear positive cases notified divided by the number of new smear positive cases estimated for that year, expressed as a percentage.

Associated terms

Smear-positive: a case of TB where Mycobacterium tuberculosis bacilli are visible in the patient's sputum when examined under the microscope. For exact definition, see WHO, 2007.

New case: TB in a patient who has never received treatment for TB, or who has taken anti-TB drugs for less than 1 month.

DOTS: the internationally recommended approach to TB control, which forms the core of the Stop TB Strategy (WHO, 2006b). The five components of DOTS are:

• Political commitment with increased and sustained financing;
• Case detection through quality-assured bacteriology;
• Standardized treatment with supervision and patient support;
• An effective drug supply and management system; and
• A monitoring and evaluation system, and impact measurement.

In countries that have adopted the DOTS strategy, it may be implemented in all or some parts of the country, and by all or some health-care providers. Only those TB cases notified by health-care facilities providing DOTS services are included in this indicator.

Notification: the process of reporting diagnosed TB cases to WHO; the data collected by this process. This does not refer to the systems in place in some countries to inform national authorities of cases of certain ‘notifiable’ diseases.

Data sources

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.

Estimated number of incident cases: see Dye C et al., 1999; Corbett EL et al., 2003; and WHO, 2007, and description of estimation of incidence.

Methods of estimation

Estimates of incidence are based on a consultative and analytical process in WHO and are published annually (see WHO, 2007).

The DOTS detection rate for new smear-positive cases is calculated by dividing the number of new smear-positive cases notified to WHO by the estimated number of incident smear-positive cases for the same year.

Disaggregation

Detection rates are routinely presented by WHO in four main ways:

• For new smear-positive cases;
• For all new and relapse cases (i.e. all forms of TB);
• For DOTS programmes only; or
• For cases notified from all sources.

It is the detection rate of new smear-positive cases for DOTS programmes that is included in this database.

References

Database

Comments

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 do smear-negative patients. However, national TB control programmes should aim to provide treatment to all patients, as set out in the Stop TB Strategy.