ONCOCHECK - AN INTERNATIONAL EXTERNAL QUALITY ASSESSMENT SCHEME FOR IMMUNOASSAYS OF TUMOR-MARKERS

Starting from November 1990, an international External Quality Assessm ent Scheme (EQAS) for immmunoassays of tumor markers has been organize d. Presently, 238 laboratories from France, Germany, Italy, Japan and Spain participate in the scheme. In this report the main features of t he EQAS and data processing are outlined. Results collected during the 1992-cycle allow evaluation of the state of the art of AFP, CEA, CA 1 9-9, CA 15-3, GA 125 and PSA immunoassays. According to their analytic al performances the 6 tumor marker immunoassays can be classified into several groups, the first including AFP and CA 15-3 for wich both tot al variability and within-kit agreement are good. For CEA assay, perfo rmance can be considered as satisfactory even though further improveme nts of between-lab agreement would be welcome. For the 3 other tumor m arkers, the higher total variability indicates an urgent need for a be tter standardization by improvement of either both within-kit and betw een-kit agreements (CA 19-9) or between-kit agreement mainly (PSA, CA 125).