Quality assessment of tumor marker determinations: a proposal for a supraregional scheme.

The use of tumor marker tests has increased progressively in the last decade concomitant with the advent of new monoclonal antibodies and their growing use in clinical oncology for various follow-up programs. External quality assessment (EQA) schemes widely adopted in clinical chemistry, have been extended in the last decade to immunoassays of hormones and tumor markers. EQA results can provide realistic information on the quality of the assays, performed under routine conditions. The goal of this article is to report the main results and discrepancies encountered so far in External Quality Assessment programs on tumor markers.