Is skin testing required for antibiotics (Antibacterial medications)?

From the Guidelines

Skin testing for antibiotics is generally not routinely needed before administering most antibiotics, but it may be appropriate in specific situations, particularly for patients with a history of severe allergic reactions to penicillins or other beta-lactam antibiotics. For penicillin allergies, standardized skin testing protocols exist using major and minor determinants (Pre-Pen and penicillin G) 1. The procedure involves first performing a skin prick test, followed by intradermal testing if the prick test is negative.

Key Points to Consider

• The negative predictive value of penicillin skin testing is between 97% and 99%, and the positive predictive value is at least 50% 1.
• Skin testing is most useful when there's a compelling need to use a specific antibiotic in a patient with a concerning history of reaction.
• If skin testing is negative, a supervised graded challenge or desensitization may still be necessary depending on the severity of the previous reaction and the certainty of the diagnosis.
• For other antibiotics like cephalosporins, sulfonamides, or fluoroquinolones, standardized testing materials and protocols are less established, making testing less reliable.

Recommendations

• Skin testing should be considered for patients with a history of severe allergic reactions to penicillins or other beta-lactam antibiotics.
• The testing helps identify patients who may have lost their sensitivity over time or were never truly allergic.
• This is important because antibiotic allergies often lead to the use of broader-spectrum, more expensive, or less effective alternative antibiotics.

Limitations and Considerations

• The availability of skin testing reagents, including minor determinants, may be limited in some areas 1.
• Experts suggest caution when the full battery of skin-test reagents is not available, as skin testing without the minor determinants would still miss 3%-10% of allergic patients 1.

From the Research

Skin Testing for Antibiotics

• Skin testing is a method used to diagnose allergies, including those to antibiotics such as penicillin 2, 3, 4.
• The test involves introducing a small amount of the antibiotic into the skin to check for an allergic reaction 5.
• Penicillin skin testing (PST) is a simple and reliable way of diagnosing penicillin allergy, with a negative predictive value (NPV) of 100% in one study 2.
• Skin testing can help identify patients who are at low risk of developing an immediate-type hypersensitivity reaction to β-lactam antibiotics 2, 3.

Types of Skin Testing

• There are two types of skin testing used in clinical practice: percutaneous testing (prick or puncture) and intracutaneous testing (intradermal) 5.
• Prick testing involves introducing a needle into the upper layers of the skin through a drop of allergen extract, while intradermal testing involves injecting a small amount of allergen into the dermis 5.
• Prick testing methods are the initial technique for detecting the presence of IgE and may correlate better with clinical sensitivity, but are less sensitive than intradermal testing 5.

Determinants in Penicillin Allergy Testing

• Major and minor determinants are used in penicillin allergy testing, including penicilloyl-polylysine (PPL) and minor determinant mixture (MDM) 3, 4.
• The use of PPL and MDM in skin testing can help identify patients who are at risk of an allergic reaction to penicillin, with an average NPV of 97.9% in history-positive patients 3.
• Benzyl penicillin and amoxicillin alone may be sufficient for in vivo testing in suspected individuals with penicillin allergy 4.

Clinical Practice and Antibiotic Stewardship

• Skin testing can help improve antibiotic stewardship in the hospital setting by identifying patients who can safely receive β-lactam antibiotics 2, 6.
• The use of skin testing can also help reduce costs and improve patient outcomes by minimizing the use of alternative antibiotics 2, 6.
• Critical care providers should evaluate antibiotic allergy using nonirritating concentrations before administering antibiotics to patients 6.