Eligibility criteria
Prospective, retrospective, cross-sectional, and case-control studies
were included in our study examining CRD in the diagnosis of milk
allergy in children or adults. Studies needed to include sIgE measured
for at least one milk allergen component (Bos d 4, 5, 6, 8) and provide
sufficient data to calculate the following four relevant diagnostic
indices: sensitivity, specificity, PPV, and NPV. Oral food challenge
(double-blind or open) was the reference standard, and at least 50% of
patients received OFC. We excluded secondary studies (e.g., reviews or
systematic reviews), case reports, and animal studies. Only full-text
available articles were included.