Tuberculosis classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Classification

Below is a table with the current classification system of tuberculosis (TB), based on its pathogenesis:

Class	Type of Tuberculosis	Description
0	No TB exposure Not infected	No history of TB exposure Negative result to a TST or IGRA
1	TB exposure No evidence of infection	History of TB exposure Negative result to a TST (given at least 8-10 weeks after exposure) or IGRA
2	TB infection No TB disease	Positive result to a TST or IGRA Negative smears and cultures (if done) No clinical or x-ray evidence of active TB disease
3	Clinically active TB	Positive culture (if done) for M. tuberculosis Positive result to a TST or IGRA, and clinical, bacteriological, or x-ray evidence of TB disease
4	Previous TB disease (not clinically active)	Medical history of TB disease Abnormal but stable x-ray findings Positive result to a TST or IGRA Negative smears and cultures (if done) No clinical or x-ray evidence of active TB disease
5	Suspected TB	Signs and symptoms of TB disease, but evaluation not complete

CDC TB Classification for Immigrants and Refugees

The U.S. Citizenship and Immigration Services has an additional TB classification for immigrants and refugees developed by the Centers for Disease Control and Prevention (CDC). The 'B Notification Program' is an important screening strategy to identify new arrivals who have a high risk for TB.

United States Immigrant/Refugee TB Classification

Class	Chest X-ray	AFB smear	Restrictions
A - TB, infectious	Active TB	Positive	No entry to U.S. until treated and smears are negative
B1 - TB, clinically active, not infectious	Active TB	Negative	Report to local health department for further medical evaluation within 30 days of arrival in U.S.
B2 - TB, not clinically active	Inactive TB	Not required unless symptomatic	Same as above
No class (Normal)	Normal	Not required	None