Context Clinicians frequently withhold antibiotics that contain penicillin based
on patients' self-reported clinical history of an adverse reaction to penicillin
and the clinicians' own misunderstandings about the characteristics of a true
penicillin allergy.
Objectives To determine the likelihood of true penicillin allergy with consideration
of clinical history and to evaluate the diagnostic value added by appropriate
skin testing.
Data Sources MEDLINE was searched for relevant English-language articles dated 1966
to October 2000. Bibliographies were searched to identify additional articles.
Study Selection We included original studies describing the precision of skin testing
in diagnosis of penicillin allergy. We excluded studies that did not use both
minor and major determinants, provide an explicit definition of penicillin
allergy, or list the specific criteria necessary for a positive skin test
result. Fourteen studies met the inclusion criteria.
Data Extraction Three authors independently reviewed and abstracted data from all articles
and reached consensus about any discrepancies.
Data Synthesis Patients' self-reported history has low accuracy for diagnosis of true
penicillin allergy. By evaluating studies comparing clinical history to the
skin test for penicillin allergy among patients with and without a positive
history for penicillin allergy, positive and negative likelihood ratios were
calculated. History of penicillin allergy had a positive likelihood ratio
of 1.9 (95% confidence interval [CI], 1.5-2.5), while absence of history of
penicillin allergy had a negative likelihood ratio of 0.5 (95% CI, 0.4-0.6).
Conclusions Only 10% to 20% of patients reporting a history of penicillin allergy
are truly allergic when assessed by skin testing. Taking a detailed history
of a patient's reaction to penicillin may allow clinicians to exclude true
penicillin allergy, allowing these patients to receive penicillin. Patients
with a concerning history of type I penicillin allergy who have a compelling
need for a drug containing penicillin should undergo skin testing. Virtually
all patients with a negative skin test result can take penicillin without
serious sequelae.