What is an intradermal test?
The intradermal test is widely used to support the diagnosis of dermatological and non-dermatological diseases. They are mainly indicated for the detection of immediate hypersensitivity (type I hypersensitivity) and delayed (DTH, type IV hypersensitivity) to exogenous or endogenous antigens. Intradermal tests are for the diagnosis of infectious diseases related to dermatovenerology are discussed in this section.
They are suggested to detect DTH in organisms or their antigens. Before performing an intradermal test, it is advisable to discontinue or avoid systemic steroids or immunosuppressive agents at least three days before the procedure.
Intradermal allergy testing is another skin test method to determine if a person is allergic to a particular allergen. The test involves injecting a suspected allergen under the surface of the skin. After approximately 20 minutes, the area is examined for an on-site reaction.
A common reaction is swelling and redness that looks like a small hive. The intradermal test is much more sensitive than the skin prick test and generally provides more consistent results.
Materials and methods
All tests performed in this detailed prospective study were part of the overall investigation in patients referred for investigation of DH and no additional tests were performed. Information on the method used to manage IDs was collected with a special interest in DH from the databases of 11 departments in Europe.
The following data were recorded: age and sex of the patient, method of filling the syringe, injection volume of saline and amoxicillin (AX), injection site and diameter of the Wi and 20 min after injection. . For AX (20 mg/ml), parenteral AX powder (may vary by manufacturer and dispensed by the local hospital pharmacy) is dissolved in pure isotonic saline and used within 2 hours of IDT as recommended.
Two methods used to fill syringes with 0.02 ml of normal saline (NS) were examined at participating centers. In nancy, three specialist nurses in an allergy workshop took exactly 0.02 ml into a 1 ml syringe with a 25 G needle and then emptied it into a small vial (Method 1).
Another nurse filled a syringe with 0.05-0.07 ml of saline solution, then expelled the extra liquid and air bubbles to make 0.02 ml, emptied in the same way into a vial (procedure 2). The two procedures were repeated 10 times in a row.
The weight of NS collected by the two methods was determined using an accurate balance (KERN EW / EG version 2.4 11/2006) and then converted into milliliters. Method 2 was also performed in Copenhagen using a 1 ml syringe similar to Nancy’s, and a 0.5 ml syringe and a 27 G needle were used in both cases.
The first part of the study was conducted to determine if adherence to previously published international guidelines reduces the diversity between centers in RTD; Each participating center demonstrated IDT with NS and AX test solutions (20 mg/ml) using their native IDT protocol.
In the second part of the study, the ENDA method, injecting a constant volume (0.02 ml) of AX or NS, was performed on additional new patients.
The injection sites used for saline or AX IDT are the flexor factor of the upper arm (UA) and/or forearm (FA), and in a limited number of patients, the posterior (B). All centers used 25-27 G needles except one, of which 30 G needles were used.
Injection sites were inspected immediately after injection, with a measurement of Wi and 20 minutes after injection for the wheel (W20) and erythema (E20), respectively, and their diameter as recommended.
Intradermal test for bacterial infections
It helps a lot in classifying leprosy. It should not be used for diagnostic purposes because it is positive in a large number of the general population and negative for the leprosy pole of the disease.
Two types of antigens are available
Lepromin Mitsuda, an autoclaved suspension of tissue (whole bacilli) derived from experimentally infected armadillos (lepromin A); And Dharmendra promise, a refined chloroform-ether suspension of M. lepra (differentiated bacilli with soluble protein components).
The response after intradermal injection is usually biphasic, with an early fernández reaction and a late Mitsuda reaction. Both responses are expressions of MIC to the antigen. In India, the lepromin antigen is manufactured by the central leprosy teaching and research institute in chengalpattu, Tamil Nadu.
The anthrax skin test, which measures DTH for anthrax antigens, has been used as a diagnostic tool. It is also recommended by the WHO to assess immunological memory against anthrax. Anthrax, B. Vegetativo de anthracis (stern strain), cell wall extract from a non-encapsulated strain, composed mainly of peptidoglycans and polysaccharides.
Anthrax is made by using a cell wall extract in place of the vaccine antigen. Therefore, an anthrax skin test can detect the difference between exposed and unexposed individuals, even if they have acquired immunity.
In most cases (80%), anthrax skin test turns positive during the first three days of illness and remains positive for a long time after recovery from illness. Therefore, the anthrax skin test appears to be a valuable method for the early diagnosis of acute anthrax and is the only method to reconsider the diagnosis of human anthrax.
Frei’s test was developed in 1925 for lymphogranuloma venereal (LGV) and uses Frei’s antigen. This indicates a delayed hypersensitivity to the standardized intradermal antigen produced from chlamydia grown in the yolk sac of the chicken fetus. The test is read 48 hours later and again on the fourth day. A nodule larger than 5 mm on the fourth day was considered a positive response.
A positive test indicates a past or present chlamydia infection. Free’s test becomes positive two to eight weeks after infection. Free’s antigen is common to all chlamydial species and is not unique to LGV. Due to its specific nature, the test can no longer be used.