Differences among heat-treated, raw, and commercial peanut extracts by skin testing and immunoblotting.
BACKGROUND
Peanut allergenicity has been reported to be influenced by heat treatment, yet the commonly available extracts for skin prick testing (SPT) are derived from raw extracts.


OBJECTIVE
To assess the effect of heat treatment on the SPT reactivity and specific IgE binding to peanut.


METHODS
Three commercial extracts and 3 laboratory-prepared extracts, including raw, roasted, and boiled, were used for SPT in 19 patients with suspected peanut allergy and in 4 individuals who eat peanut without any symptoms. Serum samples were obtained to measure total IgE in addition to specific IgE binding to the study extracts by immunoblotting. Peanut allergy was confirmed with challenge test unless the individual had a convincing history of a severe reaction.


RESULTS
Eleven study participants were considered peanut allergic based on a strong history or positive challenge test result. SPT with the prepared and commercial reagents showed that the boiled extract had the highest specificity (67% vs 42%-63% for the other extracts). The prepared extracts showed similar SPT sensitivity (81%). Three patients with a history of severe reaction and elevated specific IgE levels to peanut to the 3 study extracts had variable SPT reactivity to 1 or more of the commercial extracts. IgE binding to Ara h 2 was found in nearly all patients, regardless of their clinical reactivity.


CONCLUSIONS
None of the extracts tested showed optimal diagnostic reliability regarding both sensitivity and specificity. Perhaps testing should be performed with multiple individual extracts prepared by different methods.
US Department of Agriculture, Agricultural Research Service, New Orleans, Louisiana, USA.
Soheila J
SJ
Maleki
Adrian M
AM
Casillas
Ujwala
U
Kaza
Brian A
BA
Wilson
Jacqueline B
JB
Nesbit
Chantrel
C
Reimoneqnue
Hsiaopo
H
Cheng
Sami L
SL
Bahna
D000485:Allergens / Q000276:immunology; D010367:Arachis / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006358:Hot Temperature; D006801:Humans; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D007223:Infant; D008297:Male; D021183:Peanut Hypersensitivity / Q000097:blood / Q000175:diagnosis*; D010936:Plant Extracts / Q000276:immunology; D012882:Skin Tests / Q000379:methods*
D000485:Allergens; D010936:Plant Extracts; D007073:Immunoglobulin E