COMPARISON OF MODIFIED PHADEZYMRAST, IMMUNOCAP, AND SERIAL DILUTION TITRATION SKIN TESTING BY RECEIVER OPERATING CURVE ANALYSIS

Improved technology in in vitro tests for allergen-specific immunoglob ulin E has led to increased efficiency and faster turnaround times. Im munoCAP (Pharmacia Diagnostics, Clayton, N.C.) is an in vitro-specific immunoglobulin E test that uses a three-dimensional cellulose solid a llergen phase, which allows quick results in 6 hours. In comparison, m odified PhadezymRAST (Pharmacia Diagnostics) uses a two-dimensional so lid phase, and results take 3 days to obtain. This study compares the sensitivity and specificity of CAP with that of modified RAST in the d etection of specific immunoglobulin E, and it assesses the correlation of the individual class scores of CAP and modified RAST with end poin ts obtained from skin-dilutional end-point titration. The reproducibil ity of CAP was also assessed. Patients evaluated at the University of Chicago Allergy Clinic who had a history and physical examination cons istent with immunoglobulin E-mediated allergy and in whom skin testing was clinically indicated as part of their allergy management, were as ked to donate some blood for simultaneous in vitro testing by Phadezym RAST and ImmunoCAP. Testing was performed in batches. Random samples f rom the CAP batches were chosen for duplicate runs under conditions bl inded to the technician. Receiver operating curve analysis was used fo r comparison of the sensitivity and specificity of RAST vs. that of CA P. We used Pearson product-moment correlation coefficients to compare the correlation of RAST and CAP classes with the end points from skin testing. Our results indicate that the sensitivity and specificity of RAST and CAP are similar, that the classes of these two tests correlat e well with the end points from skin testing, and that duplicate sampl es of CAP also correlate well.