Latent TB Infection (TB Infection) | CDC

NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.

CSTE Position Statement(s)

  • 17-ID-09

Background

TB is a disease caused by a bacterium called Mycobacterium tuberculosis (MTB). The active form of tuberculosis (TB Disease) was once the leading cause of death in the United States (US). TB Disease is spread through the air from one person to another when the disease is located in the lungs. People nearby may breathe in these bacteria and become infected.

Not everyone infected with M. tuberculosis becomes sick. People who are not sick have what is commonly called Latent TB Infection (TB Infection). People with TB Infection do not feel sick, do not have any symptoms, and cannot spread TB to others. Nevertheless, some people with TB Infection go on to develop TB Disease in the course of their lifetimes. Likelihood of developing TB Disease is variable depending on a number of risk factors.

Clinical Criteria

Clinical criteria alone are not sufficient to classify a case of TB Infection.Clinical criteria to confirm a suspected case of TB Infection are as follows: No clinical evidence compatible with TB Disease including: No signs or symptoms consistent with TB Disease AND

    1)Chest imaging without abnormalities consistent with TB (chest radiograph or CT scan)

OR

    • 2)Abnormal chest imaging that could be consistent with TB Disease with microbiologic testing that is negative for MTB complex

AND

    where TB Disease has been clinically ruled out

Laboratory Criteria For Diagnosis

Laboratory/diagnostic criteria alone are not sufficient to confirm a case of TB Infection. Laboratory criteria to identify suspected cases of TB Infection are as follows: A positive tuberculin skin test (TST) [As defined by the CDC (see reference)] OR A positive interferon gamma release assay (IGRA) [As defined by the CDC (see reference)]

Criteria to Distinguish a New Case from an Existing Case

A new case is an incident TB Infection case that meets the suspected or confirmed case criteria and has not previously been diagnosed or treated for TB Infection OR previously treated for TB Disease.

Case Classification

Suspected

A case that meets one or more of the laboratory criteria AND M. tuberculosis complex was not isolated from a clinical specimen, if a specimen was collected

Confirmed

A case that meets one of the laboratory criteria for TB infection AND M. tuberculosis complex was not isolated from a clinical specimen, if a specimen was collected AND Meets the clinical criteria for TB Infection as listed above

References(s)

1. Council of State and Territorial Epidemiologists (CSTE). Public Health Reporting and National Notification for Tuberculosis. CSTE Position statement 09-ID-65. Available from: http://www.cste.org/resource/resmgr/PS/09-ID-65.pdf

2. Centers for Disease Control and Prevention (CDC). Latent Tuberculosis Infection: A Guide for Primary Health Care Providers. Available from https://www.cdc.gov/tb/publications/ltbi/diagnosis.htm (Accessed February 2017)

3. Centers for Disease Control and Prevention (CDC).TB Fact Sheet on Tuberculin Skin Testing Available from: https://www.cdc.gov/tb/publications/factsheets/testing/skintesting.htm (Accessed February 2017)

4. Centers for Disease Control and Prevention (CDC). TB Fact Sheet on IGRA Blood Tests for TB infection Available from: https://www.cdc.gov/tb/publications/factsheets/testing/igra.htm (Accessed February 2017)

5. Lewinsohn DM, Leonard MK, LoBue PA et al. Official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention Clinical Practice Guidelines: Diagnosis of Tuberculosis in Adults and Children. Clin Inf Dis 2017: 64 (2): 111-5.

Page last reviewed: April 16, 2021