Experience of discordant beta hCG results by different assays in the management of non-seminomatous germ cell tumours of the testis

Fifty-five patients with non-seminomatous germ cell tumours (NSGCT) who wer e referred to a regional clinical oncology centre over a 3-year period were assessed prospectively with assays of the serum tumour markers alpha-fete protein (AFP) and beta-human chorionic gonadotropin (beta hCG). Paired base line beta hCG assays were undertaken using a polyclonal radioimmunoassay (R IA) and a monoclonal fluoroimmuno assay (FIA). Serial paired measurements w ere undertaken in patients showing discordance on baseline assays, Four pat ients (7%; 95% confidence interval 0-14) showed discordance between the pai red beta hCG assays. Of these, two showed elevated beta hCG on RIA, with no rmal levels on FIA; two showed elevated beta hCG on FIA, with normal levels on RIA. No discordance was noted with AFP assays. Discordance persisted in two of the patients (50%) and disappeared on treatment in one (25%); one p atient died during treatment. Discordant beta hCG assays present difficulties in interpretation and have therapeutic implications in patients with NSGCT. No single currently availa ble assay is conclusive in all. patients and commercial assay kits should b e chosen with care.