Fact Sheet

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Targeted Tuberculosis Testing and Interpreting Tuberculin Skin Test Results

Introduction

The Centers for Disease Control and Prevention (CDC) and the U.S. Preventive Services Task Force (USPSTF) recommend testing populations that are at increased risk for tuberculosis (TB) infection. Once TB disease has been ruled out, those who would benefit from treatment of latent TB infection (LTBI) should be offered this option regardless of their age. Treatment adherence and completion are important for those who initiate treatment.

Health care providers should consider several criteria when classifying positive TST reactions.

Table 1: Criteria for Classifying Positive TST Reactions

Positive IGRA result or a TST reaction of 5 or more millimeters of induration is considered positive in	Positive IGRA result or a TST reaction of 10 or more millimeters of induration is considered positive in
HIV-infected persons Recent contacts of a TB case Persons with fibrotic changes on chest radiograph consistent with old TB Organ transplant recipients Persons who are immunosuppressed for other reasons (e.g., taking the equivalent of >15 mg/day of prednisone for 1 month or longer, taking TNF-α antagonists)	Recent immigrants (< 5 years) from high-prevalence countries Injection drug users Residents and employees of high-risk congregate settings (e.g., correctional facilities, nursing homes, homeless shelters, hospitals, and other health care facilities) Mycobacteriology laboratory personnel Children under 5 years of age, or children and adolescents exposed to adults in high-risk categories
Positive IGRA result or a TST Reaction of 15 or more millimeters of induration is considered positive in
Persons with no known risk factors for TB*
* Although skin testing programs should be conducted only among high-risk groups, certain individuals may require TST for employment or school attendance. An approach independent of risk assessment is not recommended by CDC or the American Thoracic Society.