The World He alth Organization estimates that two billion people worldwide have latent tuberculosis, and about three million people worldwide die from tuberculosis every 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 to the bacterium that causes tuberculosis (TB). This body reaction can occur if someone currently has TB, if they have been exposed to it in the past, or if they have received the BCG vaccine for TB.
Tuberculin test
The tuberculin skin test is based on the fact that tuberculosis infection induces a delayed-type hypersensitivity reaction to certain components of the bacterium. Body components are extracted from tuberculosis cultures and are the main elements of classic tuberculin PPD. This PPD material is used for testing. The reaction in the skin to tuberculin PPD begins when specialized immune cells called T cells have been sensitized by a previous infection,are attracted by the immune system to a site of skin where they release chemicals called lymphokines. These lymphokines induce induration (a hard area with well-defined margins at and around the injection site) through local vasodilation (expansion of the diameter of blood vessels), resulting in fluid deposition known as edema, fibrin deposition, and recruitment of other types of inflammatory cells to the area.
An incubation period of 2 to 12 weeks is usually required after exposure to TB bacteria for a PPD test to be positive. Anyone can be tested for TB, and it can be done on infants, pregnant women or HIV-infected people without any danger. It is only contraindicated in people who have had a severe reaction to a previous tuberculin skin test.
How is the TB test administered?
The standard recommended tuberculin test, known as the Mantoux test, is administered by injecting 0.1 ml of a liquid containing 5 IU (tuberculin units) of PPD into the upper layers of the skin (intradermally, just below the surface of the skin) of the forearm. It is recommended to use an area free from anomalies and from a vein. The injection is usually given using a 27-gauge needle and a tuberculin syringe. Tuberculin PPD is injected directly under the surface of the skin. With proper injection, a discrete, pale skin elevation of 6-10 mm in diameter should be produced. This "bubble" is usually quickly absorbed. If it is determined that the first test was entered incorrectly, another one may be assigned immediately.
Evaluation of the result
Assessing a mantoux test in children and adults means detecting an elevated, thickened local area of skin reaction called induration. Seals are a key element to ensure that the procedure is done correctly. It is mistakenly believed that in this case redness or bruising occurs. Skin tests should be assessed 48-72 hours after injection, when the size of the lump is at its maximum. Tests read later tend to have an inaccurate compaction size and do not carry reliable information.
How to interpret skin test results ?
The basis for evaluating the result of a mantoux test is the presence or absence of a volume of induration (localized tumor). The diameter of the seal should be measured transversely (eg 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.
Tuberculin reaction is classified as a positive mantoux test result depending on the diameter of the seal in combination with certain risk factors for the individual patient. In a he althy person whose immune system is normal, an induration greater than or equal to 15 mm is considered a positive result. If blisters (vesiculation) are present, the test is also considered positive.
In some groups of people, the test is considered positive if there is a lump of less than 15 mm. For example, a sealing area of 10 mmis considered positive in the following individuals:
- Recent immigrants from areas with a high prevalence of TB.
- Residents and employees in high-risk areas for the disease.
- Drugs.
- Children under 4.
- 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 systems are suppressed.
- HIV infected.
- People with changes seen on chest x-ray that are consistent with previous TB.
- Recent contacts of people with TB carriers.
- People who have had organ transplants.
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 false negative) if their immune system is compromised by chronic illness, cancer chemotherapy, or AIDS. In addition, 10-25% of people with newly diagnosed pulmonary tuberculosis will also test negative, possibly due to poor immune systems, poor nutrition, concomitant viral infection, or steroid therapy. More than 50% of patients with extensive TB (spread throughout the body, known as miliary TB) will also test negative for TB.
A person who has received the BCG vaccine against tuberculosis can also have a positive skin reaction, although this is not always the case. This is an example of a false positive result. A positive reaction caused by a vaccine can last 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 other types of mycobacteria other than Mycobacterium tuberculosis may also have false positive skin tissue tests.
Contraindications and measures
Mantoux test contraindications are as follows.
The use of the tuberculin-derived protein, PPD, is not permitted in patients with a previous allergic reaction to the diagnostic agent or any of its components.
In addition, due to the potential for an aggravated reaction, the 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 prescriber or he althcare professional should take precautions to prevent allergic reactions.
A he althcare worker should have injections of epinephrine (1:1000) and other agents used in the treatment of severe anaphylaxis in case of a severe allergic reaction.
Before conducting a mantoux test, medical personnel should inform the patient, parent,caregiver or responsible adult about the benefits and risks of such an experience. The patient or responsible adult should report any adverse reaction following the procedure.
Vaccine administration
The TB-purified protein derivative, PPD, is for intradermal use only. It is not given through intravenous, intramuscular or subcutaneous administration. If it is given by any route other than intradermal, or if a significant portion of the dose leaks from the injection site, the test is repeated immediately, at least 5 cm from the original injection site.
Influence of disease
Patients suffering from significant immunosuppression may not respond adequately to the tuberculin-derived protein antibody, the 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 compromised by corticosteroid therapy with more than physiological doses, alkylating drugs, antimetabolites or radiation therapy.
Tuberculin skin test reaction may be suppressed within 5 or 6 weeks after stopping corticosteroids or immunosuppressants. Short-term (less than 2 weeks) corticosteroid therapy or intra-articular, bursal, or tendon injections with corticosteroids should not beimmunosuppressive.
Infections
Tuberculin Purified Protein Derivative, PPD Skin Test (Tubersol) should not be used in patients with known active tuberculosis (TB) or with a clear history of TB treatment. The presence of infection can impair cell-mediated immunity leading to depressive reactivity to the tuberculin-produced protein derivative, the PPD skin test. The person performing the procedure is advised to be aware of false-negative tuberculin reactions in patients with a current viral infection (herpes infection, measles, mumps, varicella), bacterial infection, fungal infection, suppressive tuberculosis, or in patients receiving vaccination with some live virus vaccines. It is recommended that a tuberculin skin test be performed on a separate site, or 4-6 weeks after vaccination.
Other pathologies
Reduced reactivity to tuberculin-produced protein derivative, PPD skin test may occur in patients with a concurrent disease or condition that impairs cell-mediated immunity. Negative tuberculin reaction may occur in diabetic patients; with chronic renal failure; in patients with severe protein malnutrition (> weight loss=10% of body weight) as a result of malabsorption syndrome, total gastrectomy or bypass surgery; or in patients with stressful conditions such as surgery, burns, mental illness, or reactionsvs transplant.
Acquired Immune Deficiency Syndrome (AIDS), Human Immunodeficiency Virus (HIV)
Persons with asymptomatic or symptomatic human immunodeficiency virus (HIV) infection may have an inadequate response to antibodies to tuberculin-produced protein derivative, PPD skin test. Skin test results become less reliable in HIV-infected people as the CD4 count decreases and progresses to acquired immunodeficiency syndrome (AIDS). Testing should be done as soon as possible after an HIV diagnosis. In addition, because active tuberculosis (TB) can develop rapidly in HIV-infected individuals, periodic skin testing is recommended for those patients with HIV who are at increased risk of contracting TB.
Kids
Mantou test is done for each age group. However, neonates and infants=5 mm in infants and toddlers exposed to active TB disease are considered positive. In addition, children under 4 years of age who are at risk of infection are considered positive if the skin hardening score is > 10 mm. For all other children with minimal risk, a compaction measurement of >=15mm is considered positive.
Elderly people
Sensitivity to tuberculin-produced protein derivative, PPD skin test may decrease over time and with advancing age. Geriatric patients may not wait up to 72 hours for test results, so attenuation measurements after 48 hours may not be desirable. Skin test resistance >=10 mm is considered a positive mantoux test in geriatric patients.
Pregnancy
A tuberculin-purified protein derivative, PPD is classified as FDA Pregnancy Risk Category C. There are no adequate, well-controlled studies in pregnant women; animal reproduction studies have not been conducted. It is not known whether the administration of the tuberculin skin test can cause pathological damage to the fetus or affect the reproductive system. The End Tuberculosis Advisory Board believes that tuberculin skin testing is valid and safe during pregnancy. This type of test should only be used during pregnancy if the potential benefit to the mother justifies the potential risk to the fetus.
Breastfeeding
No data available from the manufacturer regarding the use of the tuberculin-produced protein derivative, PPD, in breastfeeding mothers. However, because the test does not contain live or attenuated infectious viral or bacterial particles, the risk to the infant is considered low. The benefits of breastfeeding, the risk of potential impact on infant nutrition, and the risk of an untreated or undertreated condition must be considered. If breastfeeding for an infant has an adverse effect associated with a maternally administered drug, it is recommended that the he alth worker conducting the study report the adverse effect.
Photo of the mantoux test in the articleshows how it should look and how to measure it correctly to obtain a reliable result. There are no recommendations for the procedure. This break does not require special nutrition, giving up bad habits, and so on. If there is any suspicion of the presence of tuberculin bacillus in the body, it is necessary to visit a specialist. He will prescribe the necessary research and select the appropriate treatment.
