The atopy patch test (APT)-- a useful tool for the diagnosis of food allergy in children with atopic dermatitis.
BACKGROUND
While immediate-type clinical reactions to food can quite easily be identified by history or measurement of specific IgE in combination with positive oral food challenges, the evaluation of food allergy in the absence of immediate clinical reactions still presents diagnostic difficulties--particularly in children with atopic dermatitis. The objective of this study was to evaluate the diagnostic value of the atopy patch test (APT) with regard to late-phase reactions observed in double-blind, placebo-controlled food challenges with cow's milk, hen's egg, wheat, and soybean.


METHODS
We investigated 75 children (median age 2.1 years) with suspected food allergy by double-blind, placebo-controlled food challenges, specific IgE in serum, skin prick test, and APT. Of the subjects, 69/75 suffered from atopic dermatitis.


RESULTS
Of 209 oral challenges, 133 were performed with allergen and 76 with placebo. We assessed 77/133 allergen and 2/76 placebo challenges as positive. In 66 of 77 (86%) positive oral challenges, specific IgE in serum to the corresponding allergen was positive; in 64/77 (83%) the skin prick test, and in 42/77 (55%) the APT was positive. While immediate-type reactions were associated with positive skin prick test and proof of specific IgE in serum, late-phase clinical reactions were associated with a positive APT (sensitivity 76%, specificity 95%).


CONCLUSIONS
The APT seems to be a valuable additional tool in the diagnostic work-up of food allergy in children with atopic dermatitis - especially with regard to late-phase clinical reactions. The APT may help to prevent unnecessary restrictive diets which may be the consequence of misjudging late reactions by clinical assessment alone.
Niggemann
B
B
Department of Pneumology and Immunology, University Children's Hospital Charité of Humboldt University, Berlin, Germany.
Reibel
S
S
Wahn
U
U
D000818:Animals; D002648:Child; D002675:Child, Preschool; D003876:Dermatitis, Atopic / Q000276:immunology*; D004311:Double-Blind Method; D005260:Female; D005512:Food Hypersensitivity / Q000175:diagnosis* / Q000209:etiology / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000032:analysis; D007223:Infant; D007428:Intradermal Tests; D008297:Male; D008892:Milk / Q000009:adverse effects; D010047:Ovalbumin / Q000009:adverse effects; D010328:Patch Tests; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013025:Glycine max / Q000009:adverse effects; D014908:Triticum / Q000009:adverse effects
D007073:Immunoglobulin E; D010047:Ovalbumin