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GOAL AND TARGET ADDRESSED

Goal 6. Combat HIV/AIDS, malaria and other diseases
Target 6.C. Have halted by 2015 and begun to reverse the incidence of malaria and other major diseases

DEFINITION AND METHOD OF COMPUTATION

Definition
The proportion of tuberculosis (TB) cases detected, also known as the TB detection rate, is the number of estimated new TB cases detected in a given year using the DOTS approach) expressed as a percentage of all new TB cases.

The proportion of TB cases detected and cured, also known as the TB treatment success rate, is the number of new, TB cases in a given year that were cured or completed a full treatment of DOTS expressed as a percentage of all new TB cases.

Concepts
Tuberculosis 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.

A tuberculosis case is defined as a patient in whom tuberculosis has been bacteriologically confirmed or diagnosed by a clinician.

Case detection means that TB is diagnosed in a patient and is reported within the national surveillance system.

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 a proven TB treatment system based on accurate diagnosis and consistent treatment with a full course of anti-tuberculosis drugs (isoniazid, rifampicin, pyrazinamide, streptomycin and ethambutol). It is the first component and foundation of the internationally-recommended Stop TB Strategy, which was launched by WHO as a successor to the DOTS strategy in 2006.

Method of computation
The TB case detection rate is calculated by dividing the number of new cases notified to the World Health Organization (WHO) by the estimated number of incident cases for the same year and multiplying by 100.

The estimated number of incident cases is calculated as described for Indicator 6.9.

The TB treatment success rate is calculated by dividing the number of new, registered TB cases that were cured or completed a full course of treatment by the total number of new registered cases and multiplying by 100.

The treatment success rate is calculated based on the results of the treatment for each patient. At the end of treatment, each patient is assigned one of the following six mutually exclusive treatment outcomes: cured; completed; died; failed; defaulted; and transferred out with outcome unknown. The proportions of cases assigned to these outcomes, plus any additional cases registered for treatment but not assigned to an outcome, add up to 100 per cent of cases registered.

RATIONALE AND INTERPRETATION

Since tuberculosis is an airborne contagious disease, finding and treating cases and thus limiting the risk of acquiring infection is the primary means of controlling the spread of TB. The recommended approach to primary control is the Stop TB Strategy, an inexpensive strategy that could prevent millions of tuberculosis cases and deaths over the coming decade.

TB case detection rates and TB treatment success rates provide a measure of the effectiveness of national TB programmes in finding and diagnosing people with TB.

SOURCES AND DATA COLLECTION

Data for this indicator are derived from National TB programmes, which monitor and report cases detected, treatment progress and programme performance. Through this system, cohorts of patients can be monitored directly and accurately by making systematic evaluations of patient progress and treatment outcomes.

The number of new cases detected by national TB programmes is collected as part of the routine surveillance (recording and reporting) that is an essential component of the Stop TB Strategy. Quarterly reports of the number of TB cases registered are then compiled and sent (either directly or via intermediate levels) to the central office of the national TB control programme.

DISAGGREGATION

Disaggregated surveillance data (e.g. clinic, district, province; by age, sex) are useful for drawing out the maximum information on the TB epidemic and the impact of control measures. It is also useful, where possible, to analyze treatment success rates disaggregated by drug resistance and HIV status.

COMMENTS AND LIMITATIONS

One of the main limitations in detecting TB cases is that ministries of health in developing countries usually report only a fraction of the number of cases in the population.

Another important limitation of this indicator is that, even where treatment is of high quality, reported treatment success rates will only be high when the routine information system is also functioning well. The treatment success rate will be affected if the outcome of treatment is not recorded for all patients (including those who transfer from one treatment facility to another).

Where treatment success rates are low, the cause of the problem can only be identified by determining which of the unfavourable treatment outcomes are most common. Several factors affect the likelihood of treatment success, including the severity of disease (often related to the delay between onset of disease and the start of treatment), HIV infection, drug resistance, malnutrition and the levels of support provided to patients to ensure that they complete treatment.

GENDER EQUALITY ISSUES

See “GENDER EQUALITY ISSUES” for Indicator 6.9.

DATA FOR GLOBAL AND REGIONAL MONITORING

WHO is the agency responsible for the calculation of this indicator at the international level. Data are collected through on online data collection website used by all countries on an annual basis. Countries provide national data periodically, and 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.

Because treatment for TB lasts between six and eight months, there is a delay in assessing treatment outcomes. Each year national TB control programmes report to WHO the number of cases of TB diagnosed in the preceding year, and the outcomes of treatment for the cohort of patients who commenced treatment during the year prior to that. Data are produced annually.

The TB case notifications and treatment outcomes reported by countries follow the WHO recommendations on case definitions, recording and reporting. Data are therefore internationally comparable and there is no need for any adjustment. No imputations are made for missing values.

Regional and global estimates are produced by aggregating national estimates. To calculate the global treatment success rate, the number of new cases cured and/or with completed treatment in individual countries is divided by the total number of new cases registered for treatment in a given year.

SUPPLEMENTARY INFORMATION



EXAMPLES



REFERENCES

See “REFERENCES” for Indicator 6.9.

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