RECEIVER-OPERATING CHARACTERISTIC (ROC) CURVES - A FUNDAMENTAL TOOL FOR IMPROVING THE CLINICAL USEFULNESS OF IN-VITRO IGE TESTS

In order to establish the most efficient thresholds for serum allergen -specific IgE measured by the Pharmacia CAP System, a ''second-generat ion'' in vitro method, we evaluated results from 89 subjects with susp ected inhalant allergies, using receiver-operating characteristic (ROC ) curve analysis. Sera samples were analyzed by the Pharmacia CAP Syst em for specific IgE, the choice of allergens to be tested being based upon the symptoms and clinical history of each patient. Results were a nalyzed by ROC analysis for the five most representative allergens, ca t dander (e(1)), Dermatophagoides pteronyssinus (d(1)), Lolium perenne (g(5)), wall pellitory (W-19), and wormwood (w(5)). The areas under t he ROC curves were found to be satisfactory, ranging from 0.931 (e(1)) to 0.974 (g(5)) when we excluded w(5), which had a significantly smal ler area (0.81). To establish the most efficient threshold for each al lergen, we calculated the clinical sensitivity, specificity, efficienc y, and negative and positive predictive values. The thresholds giving a higher diagnostic efficiency were as follows: 0.40 kUa/l for d(1), 0 .55 kUa/l for g(5), 0.50 for e(1), 0.65 kUa/l for w(19), and 1.00 kUa/ l for w(5). It is concluded that quantitative reporting of specific Ig E measurement has numerous advantages, but the choice of the positive threshold seems to be a prerequisite for obtaining the optimal clinica l efficiency. It is also suggested that a specific threshold should be adopted for each allergen.