Radioallergosorbent testing for penicillin allergy in family practice.
OBJECTIVE
To determine (a) the prevalence of patients supposedly allergic to penicillin who have a positive radioallergosorbent test (RAST) result for penicillin G or V and (b) the predictive power of family physicians' clinical judgement that a patient who is supposedly allergic to penicillin will have a positive RAST result.


METHODS
Prospective multicentre cross-sectional observational study.


METHODS
Eleven primary care practices in Newfoundland; 10 were in a rural setting.


METHODS
Of 110 consecutive adult patients with a supposed allergy to penicillin 97 agreed to participate in the study; 92 underwent RAST.


METHODS
Patients helped physicians complete a questionnaire and had a venous blood sample taken for the RAST. Physicians examined the clinical history and judged whether the patient was likely to have a positive RAST result.


METHODS
Rates of positive and negative RAST results for penicillin V and G.


RESULTS
Of the 92 patients 8 had a positive RAST result and 84 a negative one. The positive predictive power of a "good" clinical history (e.g., urticaria, swollen eyes, tongue or lips, or an anaphylactic reaction witnessed by a physician) was low (10%); the negative predictive power of a "poor" clinical history (e.g., nausea, vomiting, diarrhea, fever, nonspecific rash or fainting) was 92%.


CONCLUSIONS
Less than 10% of primary care patients with a supposed allergy to penicillin will have a positive RAST result. In addition, physicians' predictions of allergy in such patients are imprecise.
Worrall
G J
GJ
Centre for Rural Health Studies, Whitbourne, Nfld.
Hull
C
C
Briffett
E
E
D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D004342:Drug Hypersensitivity / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010406:Penicillins / Q000009:adverse effects*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011852:Radioallergosorbent Test; D012680:Sensitivity and Specificity
D010406:Penicillins