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.
| 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.
| 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.
See list of notifiable diseases.