Although allergy to antibiotics is commonly claimed, true allergy to these drugs is often absent http://buff.ly/1tIbcTl. The cost of NOT testing for PCN allergy is high!This Mayo Clinic meta-analysis reviewed the role of penicillin skin testing in the evaluation and management of penicillin allergy mediated by IgE.
Major determinant
The major determinant (benzylpenicillin polylysine) detects the greatest number of penicillin allergic patients during skin testing.
Minor determinants
The minor determinants of penicillin increase the sensitivity of penicillin skin testing.
Penicillin skin testing to the major and minor determinants have a negative predictive value of 97% to 99%. The incidence of systemic adverse reaction to penicillin skin testing is less than 1%.
A detailed history of the prior reaction to penicillin is an integral part of the evaluation, but it is not accurate in predicting a positive penicillin skin test result.
Negative penicillin skin test
A patient with a negative penicillin skin test result to the major and minor determinants is at a low risk of an immediate-type hypersensitivity reaction to penicillin.
Positive penicillin skin test - what to do?
Patients with a positive skin test result should undergo desensitization to penicillin or an alternative antibiotic should be considered.
Hypersensitivity reactions to beta-lactam antibiotics: MAUS mnemonic 20-20-40-20%. Click here to enlarge the image.
Mnemonics for penicillin allergy skin testing
Major penicillin determinant test detects
Majority of patients with penicillin allergy
Minor determinant test
Minorizes the risk
References:
Penicillin skin testing in the evaluation and management of penicillin allergy. Fox S, Park MA. Ann Allergy Asthma Immunol. 2011 Jan;106(1):1-7. Epub 2010 Jul 3.
Penicillin allergy: Consider trying penicillin again. CCJM, 2003 http://buff.ly/1lutpRd
AInotes - PCN Allergy http://buff.ly/1vMAFbm
Diagnosis of Immediate Hypersensitivity to β-Lactam Antibiotics Can Be Made Safely with Current Approaches. Int Arch Allergy Immunol. 2011 Nov 1;157(3):311-317.
Penicillin and Cephalosporin allergy - Annals of Allergy, Asthma & Immunology, 2014 http://buff.ly/1ltZntr
Image source: Penicillin nucleus, Wikipedia, GNU Free Documentation License.
How to evaluate for the minor determinant in a private non university setting ? Prepen helps but then I dont know how to check for the minor determinant. Any ideas ?
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