challenge test

A provocation test is a test that simulates a natural morbid condition, causes a mild allergic episode with a small amount of allergen, and is used to determine the allergen. It is mainly used for type I allergic reactions and sometimes for the examination of type IV allergic reactions. This method can exclude false positive reactions and false negative reactions in skin tests, especially when skin tests or other tests fail to obtain positive results. Basic Information Specialist classification: Respiratory examination classification: immune examination Applicable gender: whether men and women apply fasting: not fasting Analysis results: Below normal: Normal value: no Above normal: negative: normal. Positive: Prompt allergies. Tips: Those who have a respiratory infection or a marked decrease in lung function do not perform this test. Normal value Negative reaction. Clinical significance The challenge test is divided into a specific challenge test and a non-specific challenge test. Non-specific challenge is to use heptamine or methylcholine as a mist inhalation to observe the patient's sensitivity to type I allergic reaction, so as to conduct etiological analysis or efficacy determination; specific challenge is to use antigen to test, clear allergen Have a certain value. Depending on the location of the patient, different organ stimulation tests can be performed, often with bronchial provocation test (BPT), nasal mucosal challenge test, and conjunctival challenge test. Precautions Before the test: the patient stopped the β-receptor agonist and phosphodiesterase inhibitor at least 12 hours before the test, stopped using cromolyn sodium 24 hours ago, stopped antihistamine before 48 hours, 96 hours ago Stop hydroxyzine drugs. At the time of examination: At least 30 minutes should be observed after inhalation of the allergen infusion. If necessary, it should be observed for 24 hours to facilitate the discovery of delayed reaction and biphasic reaction. After the examination: When the patient feels that the reaction is heavier, he should promptly handle it, or inhale the tracheal antispasmodic agent in time. Inspection process Abnormal results of different tests: 1. Bronchial provocation test (BPT): The criteria for the positive results are as follows: 1 obvious symptoms, such as chest tightness and wheezing; 2 lungs smell and wheezing; 3FEV-1 decreased by more than 20%. BPT is more specific than skin tests and has a strong correlation with patient history, symptoms, and allergen adsorption tests. It is commonly used to determine allergens of bronchial asthma, to test the antigenicity of new preparations, to evaluate the efficacy of antiasthmatics, and to observe the results of desensitization treatment. The shortcoming of this law is that only one antigen can be tested at a time, requiring special equipment and technology, and patient cooperation is required. 2. Conjunctival excitation test: The test side conjunctival hyperemia, edema, increased secretion, itching, and even eyelid swelling and other phenomena were positive. This test is mainly used for allergen examination of ocular allergic diseases. Note that any irritating substance in the antigen solution can cause false positives; those who have a heavier response should be washed immediately with saline. 3. Nasal mucosal stimulation test: It can be carried out by antigen inhalation method (powder) or instillation method (liquid). Mucosal edema and paleness may occur after exposure to the antigen for 15 to 20 minutes. Symptoms such as nasal itching, salivation and sneezing may be judged as positive. Mainly used to diagnose pollinosis and allergic rhinitis. If a more serious reaction occurs, the diluted norepinephrine can be used for nasal irrigation, if necessary, according to the acute onset of allergic rhinitis. 4. Oral stimulation test: The allergen is directly in contact with the oral mucosa, and the positive reaction is swelling and congestion of the oral mucosa. Mainly used for the inspection of food, drugs or other allergens. 5. Urogenital system test: The antigen is fixed to the cervix with a suitable size uterine cap and placed in the vagina; or introduced into the urethra through a catheter. The positive reaction manifested as mucosal catarrhal inflammation, and eosinophils were found in the secretions. This test is mostly used to test the sensitivity to contraceptives, genitourinary drugs and contrast agents. 6. Ice water test: The test tube filled with ice water was buckled on the back skin, and the wheal was positive after 1 min. This test has diagnostic significance for cold urticaria. Not suitable for the crowd Unsuitable for people: those who have a respiratory infection or a marked decrease in lung function do not perform this test. Adverse reactions and risks There are no related complications and hazards.