RECEIVER OPERATING CHARACTERISTIC ANALYSIS - A USEFUL METHOD FOR A COMPARISON OF THE CLINICAL RELEVANCE OF 2 IN-VITRO IGE TESTS

Background: The objectives of this study were to demonstrate the usefu lness of Receiver Operating Characteristic (ROC) analysis in the defin ition of a positive threshold in the comparison of two in vitro tests for detecting IgE antibodies and to determine the clinical relevance o f specific IgE tests according to the sensitivity and specificity dete rmined by ROC analysis. Methods: Specific IgE levels were compared wit h the use of both MATRIX (Abbott Laboratories, Chicago, Ill.) and PHAD EZYM (Pharmacia, Uppsala, Sweden) tests in 109 patients. 86 allergic p atients and 23 control subjects. All allergic patients had a clinical history of allergy to mite, cat, grass pollen, or birch pollen and pos itive skin prick test results to the suspected allergen. Using various levels of specific IgE, we determined the points of the ROC curves wi th the best ratio of true positives to false positives for four aeroal lergens (i. e., mite, cat, grass pollen, and birch pollen). Results: E xcept for mite allergen there was no correspondence between the positi ve threshold values determined by ROC analysis with MATRIX and PHADEZY M tests. In terms of class, when ROC analysis was used, the threshold was class III with the MATRIX test and class II with PHADEZYM test for cat, grass pollen, and birch pollen and class III for mite. According to the threshold value, sensitivity and specificity for MATRIX and PH ADEZYM tests were similar except for cat, for which the PHADEZYM test had a lower sensitivity (0. 71) than the MATRIX test (0.90). With mite allergen the predictive value of only one positive MATRIX test result was 0.96. The specificities of MATRIX and PHADEZYM tests were 100% in both nonatopic and atopic control groups Conclusions: We conclude tha t ROC analysis is a reliable method for comparing IgE in vitro tests a nd that it emphasizes the lack of correspondence between arbitrary uni ts given for each in vitro test. ROC analysis appears to be a good met hod for helping to standardize IgE in vitro tests.