Diagnosing peanut allergy with skin prick and specific IgE testing.
BACKGROUND
Food allergy is common in childhood. It has been suggested that the magnitude of a skin prick test or specific IgE result can improve diagnostic usefulness, but this has been addressed in only a few tertiary challenge-based studies.


OBJECTIVE
To determine the predictive value of a wheal > or = 8 mm or serum specific IgE > or = 15 kU A /L for clinical allergy and investigate whether results are generalizable.


METHODS
All subjects, up to 16 years of age, who had been investigated with a peanut or tree nut food challenge were eligible for the study. Subjects were referred from either a tertiary allergy clinic or a community birth cohort. All subjects with a history suggestive of food allergy were offered a challenge unless there were features of anaphylaxis. Details of challenges were prospectively recorded. Results were modeled by using logistic regression.


RESULTS
There was a total of 161 peanut challenges. Recent skin prick (longest wheal diameter) and specific IgE data were available for 135 and 136 challenges, respectively. The results suggest that a skin prick result > or = 8 mm and a specific IgE > or = 15 kU A /L have predictive values of 95% (95% CI, 76.2% to 99.9%) and 92.0% (74.0% to 99.0%), respectively, for a positive challenge. Age, the type of nut, and referral pattern of the subject did not appear to alter this relationship.


CONCLUSIONS
These data suggest that a skin prick result > or = 8 mm or a specific IgE > or = 15 kU A /L have a high predictive value for clinical allergy to peanut and that these cutoff figures appear generalizable to different populations of children undergoing an assessment for peanut allergy.
Roberts
Graham
G
Paediatric Allergy, Asthma and Immunology, Imperial College at St. Mary's, St. Mary's Hospital, Praed Street, London W2 1NY, UK.
Lack
Gideon
G
D000293:Adolescent; D000485:Allergens / Q000009:adverse effects; D000918:Antibody Specificity; D052179:Antigens, Plant; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood*; D007223:Infant; D008297:Male; D021183:Peanut Hypersensitivity / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D011237:Predictive Value of Tests; D012882:Skin Tests; D006113:United Kingdom
D000485:Allergens; C478880:Ana o 2 allergen, cashew; D052179:Antigens, Plant; D007073:Immunoglobulin E