No more skin test for ceftriaxone? This article will help you understand the key points of skin test

Penicillin and cephalosporin (also known as β-lactam antibiotics) are commonly used antibiotics for infectious diseases. Many patients have had this experience: before prescribing such drugs, doctors often ask patients to do a skin test (skin test). Children are very resistant to skin tests because they are afraid of pain, and parents are also very distressed about their children "getting an extra shot". They can't help but ask: Is it necessary to do a skin test when injecting antibiotics? What should be paid attention to in children's skin tests?

Because medical staff are concerned about allergic reactions induced by such drugs, penicillin and cephalosporin skin tests are widely used to predict allergic reactions before medication. However, due to misunderstandings about the mechanism of drug allergic reactions and the significance of skin tests, many medical staff rely too much on skin tests in clinical practice. Last year, the National Health Commission's Expert Committee on the Clinical Application of Antimicrobial Drugs and Bacterial Resistance Evaluation formulated the "Guidelines for Skin Testing of β-Lactam Antimicrobial Drugs (2021 Edition)". Let's take a look at skin tests.

There are four types of allergic reactions, and skin tests predict this type!

Drug allergic reactions are divided into four types: I, II, III, and IV according to different immune mechanisms. Type I is an IgE-mediated immediate allergic reaction, which usually occurs within a few minutes to an hour after administration. Typical clinical manifestations include urticaria, angioedema, bronchospasm, anaphylactic shock, etc. Type II is an antibody-mediated target cell lysis process, such as drug-induced thrombocytopenic purpura. Type III is immune complex-mediated, such as serum sickness, drug-related vasculitis, etc. Type IV is T cell-mediated, such as drug contact dermatitis, fixed drug eruption, Stevens/Johnson syndrome, toxic epidermal necrolysis, etc. Types II, III, and IV are non-IgE-mediated delayed allergic reactions, which usually occur 1 hour to several days after administration. The main purpose of the skin test for β-lactam antibiotics is to predict the possibility of type I (immediate) allergic reactions by detecting whether the patient has specific IgE antibodies (sIgE) against this type of drug and its metabolites and degradation products in the body, thereby reducing the risk of severe allergic reactions such as anaphylactic shock. The purpose of the skin test is not to predict type II, III, and IV allergic reactions, and the skin test cannot detect whether the drug contains impurities.

Is skin test still necessary? In short: Penicillin skin test, you should do it; cephalosporin skin test, do it less often!

1. Penicillins

At present, the instructions for use of penicillin antibiotics in my country, the "Guidelines for the Clinical Application of Antimicrobial Drugs" and the "Guidelines for Clinical Drug Use in the Pharmacopoeia of the People's Republic of China" all require a routine penicillin skin test before using penicillin antibiotics.

(ii) Cephalosporins

Routine skin testing before using cephalosporins is not recommended. Skin testing is only required in the following situations: ① Patients with a clear history of penicillin or cephalosporin type I (immediate-type) allergy. ② Skin testing is required as specified in the drug instructions.

Patients with a history of allergic diseases, such as allergic rhinitis, allergic asthma, atopic dermatitis, food allergies, and allergies to other drugs (non-β-lactam antibiotics) are not more likely to be allergic to cephalosporins than the general population, and routine skin tests are not required before using cephalosporins. However, if the above patients experience an allergic reaction after taking the drug, the symptoms may be more severe, and observation after taking the drug should be strengthened.

(III) Other β-lactams

For penicillins and cephalosporins β-lactamase inhibitor combination preparations, the skin test indications and methods can refer to those of penicillins and cephalosporins, respectively.

There is no evidence-based medical evidence to support the predictive effect of skin tests on other β-lactam antibiotics such as monocyclics, cephalosporins, oxacephems, carbapenems, and penems, and skin tests are not routinely performed before administration. If the instructions for these types of drugs require skin tests before use, refer to the cephalosporins. The side chain structure of aztreonam is the same as that of ceftazidime at the C7 position. Studies have reported that there is cross-allergy between the two. Patients with a clear history of ceftazidime allergy should avoid using aztreonam.

What should we pay attention to when doing skin tests on children?

Compared with skin tests, paying attention to the patient's detailed medical history is more effective in guiding the risks of medication. Therefore, it is important to provide doctors and nurses with detailed information about the child's allergy history, whether the child has an allergic constitution, whether the child is allergic to certain foods or drugs, and especially allergic drug-related situations. This information about allergies will help doctors and nurses choose the right and appropriate drugs for the child, ensure the child's medication safety, and avoid allergic reactions.

Before doing the skin test, try not to let the child be hungry or have drastic mood swings, so as to avoid symptoms such as dizziness, nausea, and abnormal distress in the child, which may be confused with allergic reactions and make it difficult to accurately judge the skin test results.

After the skin test is completed, do not press, rub, or wet the skin test site to avoid local redness caused by stimulation and false positives. Strictly abide by the skin test time. If you miss the observation time, you need to do the skin test again. During the skin test, you cannot take the child out of the ward or injection room without authorization. If the child is allergic to the drug, there will be some adverse reactions. To ensure the safety of the child, parents should not leave at will during the observation period. If you feel unwell, notify the medical staff immediately.

In short, both medical staff and patients should view skin tests correctly and understand the significance of skin tests correctly. Medical staff should follow the provisions of the "Guiding Principles" and must do skin tests when necessary and not do them when unnecessary, and adopt the correct way to prevent and deal with allergic reactions. When seeking medical treatment, the family members of the children should accurately report the details of their personal allergy history and medication history. The joint efforts of doctors and patients will ultimately be beneficial to the treatment of patients and benefit them.

Reference for this article: Guidelines for Skin Testing of β-lactam Antimicrobial Drugs (2021 Edition)

(Harbin Children's Hospital author: Liu Ziyu; reviewer: Jin Yan)