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The fraction of all incident smear-positive cases that are detected by DOTS programmes is the DOTS detection rate which is a ratio of the annual new smear-positive notifications (under DOTS) to estimated annual new smear-positive incidence (country). The value of the denominator comes from WHO's estimates for each country.

These estimates are derived from several sources of data using various methods. The methods and data vary from one country to another. The case detection rate (CDR) and the DOTS detection rate (DDR) are identical when a country reports only from DOTS areas. This should happen only when DOTS coverage is 100%. The ratio of DDR to DOTS coverage is an estimate of the case detection rate within DOTS areas, which would ideally be 70% or greater as coverage increases.

Although these indices are termed "rates", they are actually ratios. The number of case notifications is usually smaller than estimated incidence because of incomplete coverage by health services, under-diagnosis, or deficient recording and reporting. However, it is possible for the calculated detection rate to exceed 100% due to (1) intense case finding in an area that has a backlog of chronic cases, (2) over-reporting e.g. double-counting, (3) over-diagnosis, or (4) the under-estimation of incidence.

Source Publication:
World Health Organization. WHO Report 2003. Global Tuberculosis Control -- Surveillance, Planning, Financing. Geneva, 2003.

Statistical Theme: Health statistics

Created on Thursday, August 26, 2004

Last updated on Wednesday, November 30, 2005