Detection limits and receiver operating characteristic curve analysis in the evaluation of specific IgE assays

One of the major sources of uncertainty and controversy in allergy testing is the definition and clinical significance of a positive test result in the low assay range. Use of analytical detection limit theory can guide the diagnostic allergy laboratory director in setting a lower assay cutoff and in the evaluation of the recommended cutoff by the manufacturer of the assay. Several methods for calculating lower limit of detection are applicable to specific IgE assay methods. Receiver operating characteristic (ROC) curves illustrate the relationship between statistical sensitivity and specificity as cutoffs are adjusted, and statistical analysis of ROC curves is an invaluable aspect of the comparative performance evaluation of two or more assays relative to an independent standard such as skin testing.