Testing for Tuberculosis Infection

Introduction

A tuberculosis test is performed to confirm the presence of tuberculosis infection. The reason for testing, purpose, cost and test availability determine the criteria for taking a tuberculosis test. The most commonly used test for diagnosing tests is the skin test.

What Are the Types of Tuberculosis Testing?

There are two types of tuberculosis infection tests: tuberculosis skin test and tuberculosis blood test. It is not advisable to recommend both tests to confirm the diagnosis of tuberculosis infection.

• Tuberculosis Skin Test:

• The tuberculosis skin test is also named as Mantoux tuberculin test (TST). This test is carried out by a healthcare provider during two visits.

• The tuberculin skin test is the most preferred test for children under five years of age.

• A small amount of fluid called tuberculin is injected into the skin on the lower part of the arm.

• A person administered the tuberculin skin test must revisit the hospital within 48 to 72 hours to check for the reaction on the arm.

• The result is marked based on the size of the hard area or raised swelling.

• Positive Skin Test- If the person’s body is infected with tuberculosis bacteria, then the test results are considered to be positive. Additional tests such as sputum samples and chest X-rays are recommended to check if the person has tuberculosis disease or latent tuberculosis infection.

• Negative Skin Test- If the person’s body does not react to the test, there is no likelihood of tuberculosis disease or latent tuberculosis infection.

• In the case of any doubt, if required, the tuberculosis skin tests can be repeated and should be done in different locations on the body.

• Tuberculosis Blood Test:

• Tuberculosis blood tests are named interferon-gamma release assays (IGRAs).

• The patient’s blood is withdrawn and sent to the laboratory for evaluation of the results.

• Positive Blood Test- If the results are positive, then it confirms the person is infected with the tuberculosis bacteria. Other tests are performed to determine if the person has tuberculosis disease or latent tuberculosis infection.

• Negative Blood Test- If the results are negative, the absence of tuberculosis infection is confirmed.

• Indications: There are certain indications for tuberculosis blood tests, and these include the following:

• People who are not able to return back for the second appointment to look for the reaction to the tuberculin skin test.

• People who have administered the Bacillus Calmette-Guerin (BCG) vaccine.

Who Is Indicated for Testing Tuberculosis?

A certain group of people who are at high risk of being infected with tuberculosis bacteria should be tested mandatorily, and these include:

• Exposure of children and adults to the person who is at higher risk for tuberculosis disease or latent tuberculosis infection.

• Healthcare workers care for patients who are at higher risk of tuberculosis infection.

• People who were in contact with people affected with tuberculosis disease.

• People from a country, namely Asia, Eastern Europe, Russia, Latin America, and Africa, where tuberculosis infection is common.

• People who work in increased-risk places.

Who Is at High Risk of Developing Tuberculosis Infection?

• Most of the people who are infected with latent tuberculosis infection never develop tuberculosis disease.

• But in a few cases, people who have latent tuberculosis infection have an increased tendency to develop tuberculosis disease than others.

• The people who are more susceptible to developing tuberculosis include:

• Infants and young children.

• Older age groups.

• People who were not treated properly in the past.

• Sick people with weaker immune systems.

• Use of illegal drugs.

• People infected with human immunodeficiency virus.

• People who got infected with tuberculosis bacteria in the past two years.

What Are the Testing Done in Bacillus Calmette-Guerin Vaccinated Persons?

• People who are vaccinated earlier with Bacillus Calmette-Guerin may need a tuberculin skin test to confirm for tuberculosis infection.

• A previous history of vaccination with Bacillus Calmette-Guerin may show a false positive reaction to a tuberculosis skin test.

• The positive reaction of tuberculosis skin test may occur due to the infection with bacteria or due to the administration of the vaccine.

• The tuberculosis blood tests (IGRAs) are not influenced by previously administered Bacillus Calmette-Guerin vaccination.

• People who are previously injected with the Bacille Calmette-Guerin vaccination do not give false-positive results. Therefore, tuberculosis blood tests are the most preferred test for the diagnosis of tuberculosis in people done with the Bacillus Calmette-Guerin vaccine.

What Are the Screening and Testing Procedures for Healthcare Workers?

Tuberculosis testing and screening for health care workers are practiced in an attempt to control the infection. The tuberculosis screening and testing programs are carried out by people working in or volunteering in the following healthcare settings:

• Laboratories.

• Outpatient settings.

• Emergency medical services.

• Inpatient settings.

• Long-term care facilities.

• Clinical settings.

• Home-based health care and outreach settings.

• Medical settings.

In the United States, all healthcare workers need to be screened for tuberculosis prior to job placement. An annual term of tuberculosis testing is not advised for healthcare workers unless there is ongoing transmission or known exposure. The screening for tuberculosis includes:

• A tuberculosis test is done either with a tuberculosis blood test or a tuberculosis skin test.

• Tuberculosis symptom evaluation.

• Risk assessment of tuberculosis.

• Other tests evaluate for tuberculosis diseases as required.

A healthcare worker who tests positive should undergo symptom evaluation and chest X-ray to rule out tuberculosis disease. Additional evaluations are needed based on the results.

What Are the Post-Exposure Screening and Testing for Healthcare Workers?

In case of known exposure to tuberculosis disease, the healthcare personnel should undergo symptom evaluation screening and timely testing.

• Healthcare personnel shown previously with negative test results should be re-tested immediately, at least within eight to ten weeks after the last known exposure.

• No need for a re-test in the health care worker shown previously with the positive tuberculosis test result. They are advised to undergo tuberculosis symptom evaluation and other tests in the presence of any symptoms.

What Are the Tuberculosis Screening Tests During Pregnancy?

Tuberculosis skin testing is preferred and considered safe and accurate during pregnancy. Other additional tests are required if tested positive for tuberculosis. Tuberculosis blood tests are also considered safe but not used for diagnosing tuberculosis in pregnant women. There is an increased risk to both pregnant women and babies if not diagnosed and treated earlier.

Conclusion:

The tuberculosis tests are performed and designed in an attempt to control the tuberculosis infection. Various methods of screening and testing are carried out to implement in all groups of the population.