Tuberculosis classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

The current clinical classification system for tuberculosis (TB) is based on the pathogenesis of the disease.

Classification

Health care providers should comply with local laws and regulations requiring the reporting of TB. All persons with class 3 or class 5 TB should be reported promptly to the local health department. See list of notifiable diseases.

Classification System for TB

Class	Type	Description
0	No TB exposure Not infected	No history of exposure Negative reaction to tuberculin skin test
1	TB exposure No evidence of infection	History of exposure Negative reaction to tuberculin skin test
2	TB infection No disease	Positive reaction to tuberculin skin test Negative bacteriologic studies (if done) No clinical, bacteriologic, or radiographic evidence of TB
3	TB, clinically active	M. tuberculosis cultured (if done) Clinical, bacteriologic, or radiographic evidence of current disease
4	TB Not clinically active	History of episode(s) of TB or Abnormal but stable radiographic findings Positive reaction to the tuberculin skin test Negative bacteriologic studies (if done) and No clinical or radiographic evidence of current disease
5	TB suspect	Diagnosis pending TB disease should be ruled in or out within 3 months

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

Class B3 (TB, old or healed; chest X-ray with calcification) has been omitted from the classification scheme because it has not been found to be associated with active TB.

References