Tuberculosis Elimination Division – Two Step Testing

Many residential facilities, healthcare facilities, and other settings have TB screening programs. This means that employees and residents are periodically given tuberculin skin tests. The purposes of the screening program are to:

Identify people who have TB infection and possibly TB disease, so that they can be given treatment as needed

Determine whether TB is being transmitted in the facility

In a TB screening program, employees or residents are skin tested when they start their jobs or enter the facility. This is called the baseline skin test. If they have a negative skin test reaction, they may be re-tested at regular intervals thereafter. (For most employees repeat testing should be done at least once a year.)

Employees or residents whose skin test reaction converts from negative to positive between screening intervals have probably become infected with M.Tuberculosis. These skin test conversions may indicate that TB is being transmitted in the facility. People with skin test conversions are at high risk of developing TB disease because they were infected with M. Tuberculosis relatively recently (within the past 2 years).

In order to detect TB transmission and identify people who have skin test conversions, accurate information must obtained for every employee’s baseline skin test, as well as for additional skin tests.


1-‘Self Study Modules on Tuberculosis’ (1-5), Division of Tuberculosis Elimination, CDC, March 1995

Last updated September 12, 2017