What is the Mantoux Test?
The
Mantoux test, also known as the Tuberculin Skin Test (TST), is a diagnostic tool used to detect
tuberculosis (TB) infection. It involves the intradermal injection of purified protein derivative (PPD) and is commonly used in screening for TB in high-risk populations.
Purpose of the Mantoux Test
Healthcare professionals use the Mantoux test primarily to identify individuals who may be infected with
Mycobacterium tuberculosis. The test helps in determining whether someone has been exposed to TB bacteria, facilitating early intervention and treatment.
How is the Test Administered?
The test is administered by injecting 0.1 mL of PPD solution intradermally, usually on the inner surface of the forearm. A small wheal, approximately 6-10 mm in diameter, should form at the injection site. The test must be read between 48 to 72 hours after administration for accurate results.
Interpreting the Results
The results of the Mantoux test are interpreted by measuring the induration (swelling) at the injection site. Redness is not considered in the measurement. The size of the induration determines the result: 5 mm or more: Considered positive in HIV-infected individuals, recent contacts of TB cases, organ transplant recipients, and immunocompromised patients.
10 mm or more: Positive for recent arrivals from high-prevalence countries, injection drug users, and children under four years of age.
15 mm or more: Positive in individuals with no known risk factors for TB.
Factors Affecting the Test
Several factors can affect the accuracy and interpretation of the Mantoux test: BCG vaccination can cause a false-positive reaction.
Previous exposure to non-tuberculous mycobacteria may also result in a false-positive.
Immunosuppression can lead to a false-negative result.
Nursing Responsibilities
In the context of nursing, the following responsibilities are critical when conducting the Mantoux test: Preparation: Educate the patient about the procedure, including its purpose and potential side effects.
Administration: Ensure proper technique when administering the test to avoid errors in results.
Follow-up: Schedule the patient for a follow-up visit within 48 to 72 hours for test reading.
Documentation: Accurately document the size of the induration and any patient reactions.
Contraindications and Precautions
The Mantoux test should not be administered to individuals with a known severe skin reaction to the test or those with extensive skin burns or eczema. Caution should be exercised in individuals with a history of severe allergic reactions.Limitations of the Mantoux Test
While the Mantoux test is a valuable tool in TB screening, it has limitations: It cannot distinguish between latent and active TB infection.
It may not be reliable in individuals with compromised immune systems.
False positives and negatives can occur, necessitating further testing for accurate diagnosis.
Alternatives to the Mantoux Test
In cases where the Mantoux test is not applicable, alternative tests such as the
Interferon Gamma Release Assays (IGRAs) may be used. IGRAs, such as the QuantiFERON-TB Gold test, are blood tests that can help detect TB infection without the need for multiple visits.
Conclusion
The Mantoux test remains a crucial component of TB screening programs worldwide. Nurses play a vital role in administering, interpreting, and documenting the test, ensuring that individuals at risk are accurately identified and managed. Understanding the test's purpose, procedure, and limitations is essential for effective nursing care and patient education.
