Guide to the Application of Genotyping to Tuberculosis Prevention and Control

Applying Genotyping Results to Tuberculosis Control Practices

Expanded Contact Investigation


The goal of an expanded contact investigation is to ensure that all contacts of an infectious TB patient have been identified, evaluated, and treated appropriately. Although the goals of a regular contact investigation and an expanded contact investigation are the same, an expanded contact investigation involves applying greater resources to identifying and evaluating contacts, since the possibility of recent transmission to contacts has been confirmed.


Although the details of conducting an expanded contact investigation are beyond the scope of this guide, the key steps are described in this section. CDC and NTCA are developing revised guidelines for conducting contact investigations, which should be available in 2005. An additional source of information is CDC’s Self-Study Module 6, Contact Investigation for Tuberculosis, which can be ordered from CDC.

The first step in an expanded contact investigation is to ensure the completeness of the initial contact investigation of close contacts. This is most easily done by creating a database of contacts to facilitate their management. For each contact, information should be entered into the database to designate completion of each of the key components of a contact investigation: contact interview, symptom screening, tuberculin skin testing, evaluation for active TB for contacts with positive TSTs or symptoms, and treatment for LTBI, for those who require treatment. The second step in an expanded contact investigation is to include second- and third-tier contacts. These are often leisure contacts and work contacts who were not included in the initial contact investigation. The same information should be gathered for second- and third-tier contacts as was described above for close contacts identified during the routine contact investigation.


The expected outcome of an expanded contact investigation is the complete processing of all contacts of an infectious TB patient, the identification of any active cases among those contacts, and the treatment to completion, when indicated, of contacts with LTBI.