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[Diagnostic capacity of skin prick test in egg and cow's milk allergic infants]
Jun-mei Yan1, Jing Chen, Hai-qi Li
1Division of Primary Child Health Care, Children's Hospital, Chongqing Medical University, Chongqing 400014, China.
Insights
The mean wheal diameter from skin prick tests can predict food allergy in children. Specific cut-off points for egg and cow
Area of Science:
- Allergen immunotherapy and diagnostics
- Pediatric allergy and immunology
- Dermatological testing and assessment
Context:
- Food allergy diagnosis in children often involves skin prick tests (SPT) and oral food challenges (OFC).
- The mean wheal diameter from SPT is a common metric, but its predictive value for OFC outcomes requires further clarification.
- Establishing reliable SPT cut-off points could streamline the diagnostic process for suspected food allergies.
Purpose:
- To evaluate the diagnostic accuracy of mean wheal diameter in SPT for predicting positive oral food challenge outcomes in children.
- To determine specific cut-off values for mean wheal diameter that may obviate the need for OFCs in diagnosing food allergy.
- To assess the utility of SPT mean diameter in simplifying the diagnostic pathway for pediatric food allergies.
Summary:
- A study of 173 children found that mean wheal diameter from SPT accurately predicted positive OFCs for egg white, egg yolk, and cow's milk.
- Areas under the curve (AUC) ranged from 0.794 to 0.904, indicating good diagnostic capacity.
- Specific cut-off diameters (e.g., ≥ 8.5 mm for egg white, ≥ 5.5 mm for egg yolk and cow's milk) demonstrated 100% diagnostic accuracy for allergy.
Impact:
- Identified predictive decision points for positive food challenges using SPT mean diameter for common allergens like egg and cow's milk.
- Findings suggest that SPT mean diameter can potentially simplify the diagnostic procedure for food allergy in children.
- This could lead to more efficient and less burdensome allergy evaluations, reducing the need for invasive OFCs in select cases.
Objective:
Mean diameter is the most common used parameter for wheal response assessment after skin prick test. This study aimed to investigate the diagnostic capacity of mean diameter according to the outcome of oral food challenge, and to determine the cut-off points that could render food challenges unnecessary.
Method:
Data of 173 children referred to the Division of Primary Child Health Care for the evaluation of suspected food allergy were prospectively studied. All children underwent skin prick test and open food challenge to the relevant food(s) in clinic. The mean wheal diameter of skin prick test was measured, and open food challenge was performed to confirm food allergy. The SPSS software package version 13.0 for windows (SPSS, Chicago, IL, USA) was used for all statistical analysis. Open food challenge was taken as the gold standard for diagnosis. Diagnostic capacity of skin prick test, including the sensitivity, specificity, positive predictive value, negative predictive value, was calculated by cross-table. In addition, receiver operating characteristic curve (ROC) was plotted and area under the curve (AUC) was calculated to quantify the accuracy of the parameter.
Result:
For the 173 children, 271 open food challenges were performed with egg white, egg yolk and cow's milk, In which 123 were positive, 99 children were diagnosed as food allergy. Cutaneous symptoms (87.0%) were most common, followed by gastrointestinal symptoms (9.8%). The AUC of mean diameter was 0.794 for egg white, 0.804 for egg yolk and 0.904 for cow's milk. The sensitivity of skin prick test with a cut-off value of ≥ 3 mm was ranged from 71% to 87%, while the specificity was between 31% and 57%. The authors also defined food specific skin prick test mean diameters that were 100% diagnostic for allergy to egg white (≥ 8.5 mm), egg yolk (≥ 5.5 mm), cow's milk (≥ 5.5 mm).
Conclusion:
Predictive decision points for a positive outcome of food challenges can be calculated for egg and cow's milk using mean diameter. It may help to simplify the diagnostic procedure of food allergy.
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