| BackgroundAtopic dermatitis (AD) is a genetic tendency, chronic, recurrent, inflammatory skin disease, which is frequently-occurring in the infant period. The corresponding view is that Food allergy plays an important role in the pathogenesis of AD. Accurately and timely find the allergens and avoid them are the keys to treat AD of children and prevent the relapse. At present, the diagnostic work-up of suspected food allergy in China includes the patient's history, skin prick tests (SPT) and the measurement of food specific immunoglobulin E antibodies (sIgE). History is inaccurate in a substantial portion of cases, while SPT and sIgE are considered to be good tests for diagnosing immediate food hypersensitivity. They are of less help in identifying responsible allergens in delayed-onset reactions. In 1996, atopy patch test (APT) as a new diagnostic tool with high predictive capacity for late-phase clinical reactions in the diagnostic work-up of food allergy was first introduced into clinic. Since then, many researchs have demonstrated it. Nevertheless, there has been no relevant report about this in China.ObjectCompared the atopy patch test with skin prick test and aimed to investigate the ability of the APT in identifying atopic sensitization to basic foodstuffs in Chinese AD children.Methodswe performed SPT and APT at the same time and proved food allergy by oral food challenges with cow's milk (CM), hen's egg (HE), wheat, soybean and peanut in children with AD, and to compare the sensitivity, specificity, PPV, NPV and the under area of ROC curve of APT and SPT in diagnosing food allergies.Results1. Oral food challenges proved that in the study group, 49.69% had food allergies. The incidence rate of the allergies about egg, milk, soybean, wheat and peanut was 78%,60.67%,32.58%,22.76% and 45.78% respectively. Food allergies are dominated by delayed reactions, manifested mostly eczema.2. The sensitivity of APT / SPT in diagnosis of egg, milk, soybean, wheat and peanut allergies were 100%/82.9%,83.5%/90.1%,95.3%/44.2%,100%/7.1%和84.2%/28.9%, respectively. Specificity were 63.6%/63.6%,72.9%/67.8%,62.9%/74.2%,84.2%/95.8% and 75.6%/91.1%, respectively. Positive Predictive Value were 90.7%/89.0%, 81.2%/82.6%,55.4%/45.2%,65.1%/33.3% and 74.4%/73.3%, respectively. Negative predictive value were 100%/51.2%,74.1%/81.6%,96.6%/73.3%,100%/77.8% and 85.0%/60.3%, respectively.3. The sensitivity and NPV of APT in diagnosis of egg, soybean, wheat and peanut were significantly greater than SPT, but there were no significantly different in diagnosing milk allergy. The specificity of SPT in diagnosing wheat and peanut allergies were significantly higher than APT. There were no significant difference in other statistical indicators.4. The area under the ROC curves of APT/SPT in diagnosis of egg, milk, soybean, wheat and peanut allergies were 0.935/0.789,0.846/0.826,0.840/0.666,0.959/0.515 and 0.870/0.601, respectively.5. There was no significantly difference of positive rate between APT and SPT in diagnosis of immediated reactions(P=0.289), and APT had a significantly greater positive rate than SPT in diagnosis of delayed reactions(P=0.000). The sensitivity of APT and SPT in diagnosis of immediated reactions were 77.8% and 55.6% respectively, there was no significantly difference between them(χ2=2.000,P=0.157). The specificity were 85.8% and 38.1% respectively, there was significantly difference between them(χ2=85.024,P=0.000).6. Parallel APT and SPT in diagnosis of milk allergy had a significantly higher sensitivity than APT(P=0.037), but there was no significantly difference in comparing with SPT(P=0.419). Parallel diagnosis could enhence the NPV of milk allergy, but there was no significantly difference with APT(P>0.05). Parallel diagnosis could enhence the sensitivity and NPV of peanut allergy , but there was no significantly difference with APT(P>0.05). Serial diagnosis could enhence the specificity of wheat allergy , but there was no significantly difference with SPT(P=0.700). Combined diagnosis of egg and soybean allergies had a same diagnosis efficacy with APT or SPT diagnosis. There were no significantly differences between combined diagnosis and stand-alone diagnosis in PPV.Conclusion1. There was higher incidence rate of food allergy in AD children than that in ordinary children.2. Atopic patch test is a better tool than SPT in diagnosis of egg, soybean, wheat and peanut allergies, but there were no significantly different in diagnosing milk allergy.3. Atopic patch test is a better tool than SPT in reflecting clinical allergies, especially for cell-mediated reactions.4. Combined diagnosis can't increase the positive predictive value significantly compared to APT or SPT alone. |
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