The World Health Organization estimates that two billion people worldwide have latent tuberculosis, and about three million people worldwide die from tuberculosis each year. The tubercle bacillus test is also known as the tuberculin test or PPD (Purified Protein Derivative).
What is a mantoux test?
This is a test used to determine if a person has developed an immune response in response to a bacterium that causes tuberculosis (TB). This body reaction can occur if someone currently has tuberculosis, if they have been exposed to it in the past, or if they received BCG vaccine for TB.
Tuberculin test
The tuberculin skin test is based on the fact that tuberculosis infection causes a delayed-type hypersensitivity reaction to certain components of the bacterium. The components of the body are extracted from tuberculosis cultures and are the main elements of the classic tuberculin PPD. This PPD material is used for testing. The skin reaction to tuberculin PPD begins when specialized immune cells called T cells have been sensitized by a previous infection and are attracted by the immune system to the area of the skin where they release chemicals called lymphokines. These lymphokines induce densification (a solid region with distinct fields at and around the injection site) through local vasodilation (widening of the diameter of blood vessels), which leads to the deposition of fluid known as edema, the deposition of fibrin and the attraction of other types of inflammatory cells to the area.
An incubation period of 2 to 12 weeks is usually necessary after exposure to TB bacteria so that the PPD test is positive. Anyone can get tested for TB, it can be done to infants, pregnant women or HIV-infected people without any danger. This is only contraindicated in people who have had a serious reaction to a previous tuberculin skin test.
How is a tuberculosis test administered?
The standard recommended tuberculin test, known as the Mantoux test, is administered by injecting 0.1 ml of liquid containing 5 TE (tuberculin units) PPD into the upper layers of the skin (intradermally, directly beneath the skin surface) of the forearm. An area free of abnormalities and veins is recommended. The injection is usually administered using a 27th-size needle and a tuberculin syringe. Tuberculin PPD is injected directly under the skin surface. With the right injection, a discrete, pale skin lift with a diameter of 6-10 mm should be made. This “bubble” is usually quickly absorbed. If it is determined that the first test was entered incorrectly, another may be assigned immediately.
Score
Assessing a mantoux test in children and adults means detecting an increased, thickened local area of the skin reaction, called compaction. Seals are a key element in making sure that the procedure is done correctly. It is mistakenly believed that in this case redness or bruising occurs. Skin tests should be evaluated 48-72 hours after injection, when the maximum size of the seal. Tests read later, as a rule, have an inaccurate compaction size and do not carry reliable information.
How to interpret skin test results?
The basis for assessing the result of a mantle test is the presence or absence of compaction volume (localized tumor). The diameter of the seal should be measured transversely (for example, perpendicularly) to the long axis of the forearm and recorded in millimeters. The area of compaction around the injection site is a reaction to tuberculin. It is important to note that redness is not measured.
The tuberculin reaction is classified as a positive assessment of the mantoux test result depending on the diameter of the seal in combination with certain risk factors for a particular patient. In a healthy person whose immune system is normal, compaction greater than or equal to 15 mm is considered a positive result. If blisters (vesicles) are present, the test is also considered positive.
In some groups of people, the test is considered positive if a seal of less than 15 mm is present. For example, a 10 mm seal area is considered positive in the following individuals:
- Recent immigrants from areas with a high prevalence of tuberculosis.
- Residents and employees of areas at increased risk of contracting the disease.
- Drug addicts.
- Children under 4 years old.
- High risk pediatric patients.
- People who work with mycobacteria in laboratories.
A 5 mm seal is considered positive for the following groups:
- People whose immune system is suppressed.
- HIV infected
- People with changes observed on chest x-ray that correspond to previous tuberculosis.
- Recent contacts of people with carriers of tuberculosis.
- People who have transplanted organs.
On the other hand, a negative Mantoux test does not always mean that a person does not have tuberculosis. People who have been infected may not have a positive skin test (known as a falsely negative result) if their immune system is compromised by chronic diseases, cancer chemotherapy, or AIDS. In addition, 10–25% of people with newly diagnosed pulmonary tuberculosis will also have a negative result, possibly due to a poor immune system, poor nutrition, concomitant viral infection, or steroid therapy. More than 50% of patients with extensive tuberculosis (common throughout the body known as miliary tuberculosis) will also have a negative tuberculosis test.
A person who has received BCG vaccine against tuberculosis may also have a positive skin reaction, although this is not always the case. This is an example of a false positive result. The positive reaction caused by the vaccine can persist for many years. Those who were vaccinated after the first year of life or who had more than one dose of the vaccine are more likely to have a permanent positive result than those who were vaccinated in infancy.
People who are infected with types of mycobacteria other than Mycobacterium tuberculosis may also have false positive tests for skin tissue.
Contraindications and measures
Mantoux test contraindications are as follows.
The use of tuberculin-derived protein derivative, PPD, is not permitted for patients with a previous allergic reaction to the diagnostic agent or any of its components.
In addition, due to a possible exacerbated reaction, a tuberculin skin test should not be administered to anyone who has previously experienced severe skin reactions such as vesiculation, ulceration or necrosis.
When using a biological product, the prescribing authority or medical professional must take precautions to prevent allergic reactions.
The healthcare provider should have an injection of adrenaline (1: 1000) and other agents used in the treatment of severe anaphylaxis in the event of a serious allergic reaction.
Before conducting a mantoux test, medical personnel must inform the patient, parent, guardian, or responsible adult of the benefits and risks of such a swab. The patient or responsible adult should report any adverse reaction after the procedure.
Vaccine administration
A tuberculosis-purified protein derivative, PPD, is for intradermal administration only. It is not given through intravenous, intramuscular or subcutaneous administration. If it is given in any way, except intradermally, or if a significant portion of the dose flows from the injection site, the test is repeated immediately, at least 5 cm from the original site.
The impact of disease
Patients suffering from significant immunosuppression may not have adequate reaction to the antibody to the tuberculin-produced protein derivative, PPD skin test. Immunosuppressive people are patients:
- with generalized neoplastic disease;
- with diseases affecting the lymphoid organs (Hodgkin's disease, lymphoma, chronic leukemia, sarcoidosis);
- with diseases of the immune system that are compromised by corticosteroid therapy with more than physiological doses, alkylating drugs, antimetabolites, or radiation therapy.
A reaction to a tuberculin skin test can be suppressed within 5 or 6 weeks after cessation of corticosteroids or immunosuppressants. Short-term (less than 2 weeks) corticosteroid therapy or intra-articular, bursal or tendon injections with corticosteroids should not be immunosuppressive.
Infections
Tuberculin Purified Protein Derivative, PPD Skin Test (Tubersol) should not be used in patients with reported active tuberculosis (TB) or with a clear history of tuberculosis treatment. The presence of infection can impair cell-mediated immunity, leading to depressive reactivity to the tuberculin-produced protein derivative, PPD skin test. The person who is carrying out the procedure is advised to know the false-negative tuberculin reactions in patients with ongoing viral infection (herpes, measles, mumps, chickenpox), bacterial infection, fungal infection, suppressing tuberculosis, or in patients receiving vaccination with some live virus vaccines. It is recommended to conduct a tuberculin skin test in a separate area, or 4-6 weeks after the administration of the vaccine.
Other pathologies
Reduced reactivity to the tuberculin-derived protein derivative, PPD skin test can occur in patients with a concurrent disease or condition that impairs cell-mediated immunity. A negative tuberculin reaction may occur in patients with diabetes mellitus; in chronic renal failure; in patients with severe protein malnutrition (weight loss> = 10% of body weight) as a result of malabsorption syndrome, total gastrectomy or shunting; or in patients with stressful conditions, such as surgery, burns, mental illness, or anti-transplant reactions.
Acquired Immunodeficiency Syndrome (AIDS), Human Immunodeficiency Virus (HIV)
Individuals with asymptomatic or symptomatic infection of the human immunodeficiency virus (HIV) may have an inadequate response to antibodies to the tuberculin-produced protein derivative, PPD skin test. Skin test results become less reliable in HIV-infected people as CD4 count decreases and progresses to Acquired Immunodeficiency Syndrome (AIDS). Testing should be done as soon as possible after the diagnosis of HIV. In addition, since active tuberculosis (TB) can develop rapidly in HIV-infected individuals, periodic skin testing is recommended for those HIV patients who are at increased risk of contracting TB.
Kids
A mantle test is done for each age group. However, newborns and infants <6 weeks old do not have a test, because their immune system is not fully ripe, can not respond to a skin test, leading to false-negative reactions. Thus, the mantle test result in children, measured> = 5 mm in infants and young children exposed to active tuberculosis diseases, is considered positive. In addition, children under 4 years of age who are at risk of infection are considered positive if the skin tightness is> 10 mm. For all other children with minimal risk, a seal measurement> = 15 mm is considered positive.
Aged people
Sensitivity to the tuberculin-derived protein derivative, the PPD skin test, may decrease over time and with advanced age. Geriatric patients may not wait for test results up to 72 hours, so measuring attenuation after 48 hours may be undesirable. Stability of the skin test> = 10 mm is considered a positive mantle test in geriatric patients.
Pregnancy
A tuberculin-purified protein derivative, PPD, is classified as an FDA C pregnancy risk category. There are no adequate, well-controlled studies in pregnant women; animal reproduction studies have not been conducted. It is not known whether the introduction of a tuberculin skin test can cause pathological damage to the fetus or affect the reproductive system. The Advisory Board for the Elimination of Tuberculosis believes that tuberculin skin tests are valid and safe during pregnancy. This kind of test should be used during pregnancy only if the potential benefit to the mother justifies the possible risk to the fetus.
Breast-feeding
There is no data from the manufacturer regarding the use of the tuberculin-derived protein derivative, PPD, in nursing mothers. However, since the test does not contain live or attenuated infectious viral or bacterial particles, the risk to the infant is considered low. Consideration should be given to the benefits of breastfeeding, the risk of potential effects on baby food, and the risk of an untreated or insufficiently processed condition. If breastfeeding for an infant has an adverse effect associated with a maternally administered drug, it is recommended that the health worker conducting the study report an adverse effect.
A photo of the mantoux sample in the article shows how it should look and how to correctly measure it to obtain a reliable result. There are no recommendations for the procedure. This jerking does not require special nutrition, refusal of bad habits and other things before conducting it. If there is any suspicion about the presence of tuberculin bacillus in the body, it is necessary to visit a specialist. He will prescribe the necessary study and select the appropriate treatment.