What is the concentric circle approach?
The concentric circle approach is a method of testing contacts in order of their exposure time (close vs. other-than-close) and risk (high priority vs. low priority), with the close contacts and other contacts at high risk of developing TB disease tested first. In this approach, the original TB patient (the index case) is at the center. The circle is divided into three concentric rings to represent the three levels of risk: close (high risk), other-than-close (medium risk), and other-than-close (low risk). The circle is also divided, like a pie, into segments that represent the three types of environment where the contact may have taken place: • Household or residential • Work or school • Leisure or recreation environments The highest-priority group, consisting of close contacts and of people at high risk of developing TB disease, is circle closest to the index circle. This means that this group is tested first. Close contacts can be found in each segment of the concentric circle (i.e.
