The Rational Clinical Examination
David L. Simel, Drummond Rennie
Penicillin Allergy
Alan R. Salkind, Paul G. Cuddy, John W. Foxworth
Immediate Reactions
Topics Discussed:
allergy to penicillin, beta-lactam antibiotics, drug interactions, finding the evidence, penicillin, penicillin adverse reaction
Excerpt:
"We searched MEDLINE for English-language literature dated from
1966 to October 2000 by using the following Medical Subject Headings
and search strategy: (1) "medical history taking" or "physical
examination" and "penicillin" or "
-lactam
hypersensitivity" and (2) "reproducibility of results" or "observer
variation" and "penicillin" or "-lactam
hypersensitivity." A textword search was also performed
with "interobserver," "intraobserver," "accuracy," "precision," "reliability," "sensitivity," "specificity," "skin
testing," and "penicillin" or "-lactam
hypersensitivity" or "allergy." The bibliographies
of pertinent articles were searched to identify additional references. Included
articles were original studies conducted on ambulatory or hospitalized
children or adults describing the accuracy or precision of skin
testing in the diagnosis of an immunoglobulin E (IgE) –mediated
penicillin allergy. Excluded studies investigated allergy to aminopenicillins
(amoxicillin and ampicillin) or cephalosporins, did not use both
major and minor determinants in the skin testing procedure, or did
not provide an explicit definition of penicillin allergy or of a
positive skin test result. Data from patients who were reported to
have had an uninterpretable or equivocal skin test result were not
included in our analysis. Quality measures were applied, as used
in The Rational Clinical Examination series (see Table
1-7 for a summary of Evidence Grades and levels).13 Using
study quality as a measure of the relative weight that a single
study should receive was not used in our analysis, because other
authors have highlighted the pitfalls of this practice.14,15 Of the
14 studies16-29 meeting our inclusion criteria, 4
studies16-19 compared the clinical history with the
skin test result for penicillin allergy among a group of patients
with and without a positive history of penicillin allergy (Table 39-1). Confidence intervals (CIs) for
the likelihood ratios (LRs) from individual studies were computed
with a previously described method.30The frequency of all adverse reactions to penicillin in the general
population ranges from 0.7% to 10%.31 This
wide variation in the frequency of adverse reactions to penicillin
exists because of a number of variables, including exposure history,
route of administration, duration of treatment, elapsed time between
the reaction and diagnostic skin testing or reexposure, and nature
of the initial reaction. Understanding the different classifications
of penicillin hypersensitivity reactions aids evaluation of each
patient's risk for an allergic reaction that would preclude
administration of a drug that contains penicillin...."
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