Tuberculosis classification

Tuberculosis Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Tuberculosis from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Children

HIV Coinfection

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

Chest X Ray

MRI

Echocardiography or Ultrasound

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Drug-Susceptible and Drug-Resistant Tuberculosis(ATS 2025 Guidelines)

Special Conditions

Drug-resistant

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Tuberculosis classification On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Tuberculosis classification

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Tuberculosis classification

CDC on Tuberculosis classification

Tuberculosis classification in the news

Blogs on Tuberculosis classification

Directions to Hospitals Treating Tuberculosis

Risk calculators and risk factors for Tuberculosis classification

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:  Mashal Awais, M.D.[2]; João André Alves Silva, M.D. [3]

## Overview[edit | edit source]

Tuberculosis can be classified into 6 main categories according to exposure, symptoms, and diagnostic testing. The classification ranges from Class 0, in people with no previous exposure to TB and negative tuberculin skin testing and/or interferon-gamma release assay (2 methods of screening for TB), to Class 3 for active TB infection and Class 5 for suspected TB infection based on signs and symptoms of the disease. The U.S. Citizenship and Immigration Services has also designed a special classification for immigrants and refugees according to the risk of infection.

## Classification[edit | edit source]

Below is a table of the current classification system of tuberculosis (TB), according to its pathogenesis:[1]

Class | Type of Tuberculosis | Description

No TB exposure
Not infected

No history of TB exposure
A negative TST or IGRA

TB exposure
No evidence of infection

History of TB exposure
A negative TST (given at least 8-10 weeks after exposure) or IGRA

TB infection
No TB disease

Positive TST or IGRA
Negative smears and cultures (if done)
Absent clinical picture of active TB disease or abnormal x-ray findings

Clinically active TB

Positive culture (if done) for M. tuberculosis
Positive TST or IGRA, and clinical, bacteriological, or x-ray evidence of TB disease

Previous TB disease (not clinically active)

Medical history of TB disease
Abnormal but stable x-ray findings
Positive TST or IGRA
Negative smears and cultures (if done)
Absent clinical picture of active TB disease or abnormal x-ray findings

Suspected TB

Clinical manifestations of TB disease, but incomplete evaluation. The diagnosis s pending. The patient should not be in this class for more than three months.

## CDC TB Classification for Immigrants and Refugees[edit | edit source]

Based on the U.S. Citizenship and Immigration Services, developed by the Centers for Disease Control and Prevention (CDC), tuberculosis for immigrants and refugees s classified into the following categories: [2]

Class | Description | Travel Clearance

No TB Classification

Applicants with normal tuberculosis screening examinations. No discernible HIV infection and normal CXR.

| Valid for 6 months from evaluation

Class A TB

All applicants who have tuberculosis disease including applicants with extrapulmonary TB. In addition, CXR indicates pulmonary TB disease, regardless of sputum smear and culture results.

| Not cleared for travel until treatment is completed. Exceptions are available for granted waivers.
Class B0 TB, Pulmonary  | Applicants who were previously diagnosed with TB or came to the physician during the TB treatment course. Additionally, successful completion of the Division of Global Migration and Quarantine (DGMQ) prior to immigration is required.  | It can be valid for 3 months from the last negative culture results.

Class B1 TB, Pulmonary

No treatment:

* Applicants with a medical history, physical exam, or CXR findings that indicate pulmonary tuberculosis but:

* Have negative acid-fast bacilli sputum smears
* Have negative cultures
* Are not diagnosed with tuberculosis
* They can initiate tuberculosis treatment after immigration

Completed treatment:

* Applicants who had a previous diagnosis of pulmonary tuberculosis and successfully completed directly observed therapy prior to immigration
* The cover sheet must include whether the initial sputum smears and cultures were positive and if drug susceptibility testing results are available

| It can be valid for 3 months from the last negative culture results.

Class B1 TB, Extrapulmonary

Applicants with evidence of extrapulmonary tuberculosis, with normal CXR and negative sputum smears and cultures.
The anatomic site of infection should be documented

| It can be Valid for 3 months from the last negative culture results.

Class B2 TB, LTBI Evaluation

Applicants who have a TST ≥10 mm or positive IGRA but otherwise tuberculosis evaluation is negative
The TST reaction size or IGRA result, the applicant’s status regarding latent TB infection (LTBI) treatment, and the medication(s) used must be included
Applicants with more than one TST or IGRA, all results and dates must be ncluded
Contacts with TST ≥5 mm or positive IGRA should be classified according to this classification (if they are not already Class B1 TB, Pulmonary)

| Valid for 6 months from completion of evaluation.

Class B3 TB, Contact Evaluation

Applicants who have been in contact of a known tuberculosis case
The size of the applicant’s TST reaction or IGRA result must be included
The name, source case, alien number, relationship to contact, and type of tuberculosis must be included.

| Valid for 6 months from completion of the evaluation.

Risk Classification  | Necessity of testing  | Frequency of testing  |

|
|
|

Low Risk  | Settings where Tb infected individuals are unlikely to be present  | Not required unless there has been exposure to TB  |
Medium Risk  | Settings where health care workers (HCWs) are likely to encounter individuals with TB  | Testing should be repeated every year  |
Potential Ongoing Transmission  | Settings wehere person to person transmission of TB was documented in the past year  | Testing should be repeated every 8 weeks until making sure that there has been no ongoing transmission.  |

## References[edit | edit source]

1. ↑ "TB Classification".
2. ↑ "TB Classification US Citizenship and Immigration Services" (PDF).

Template:WH Template:WS