Comparison of human chorionic gonadotrophin in human urine and amniotic fluid as estimated by a polyclonal and by a specific monoclonal assay in very early pregnancy

Urinary human chorionic gonadotrophin (HCG) was estimated in 42 samples from patients in very early pregnancy or shortly after early spontaneous abortion, in which initial testing showed a positive urinary HCG in the Hybritech Tandem ICON II monoclonal 2 min test. There were no false positives with this test even when the blue colour was difficult to distinguish from the white background, i.e. considerably less than the calibration blue spot at 50 mlU/ml. The Serono polyclonal β-HCG radioimmunoassay (RIA) detected urinary intact HCG (plus free β-subunit) at concentrations as low as 10 mlU/ml IS 61/6 for bioassay (the old standard), i.e. ∼22mlU/ml 1st IRP 75/537 for immunoassay (the new standard). The LKB-Pharmacia DELFIA monoclonal fluoroimmunoassay (FIA) detected urinary intact HCG, without free β-subunit, to a minimum concentration of 18 mlU/ml 75/537. The proportion of monoclonal/polyclonal was 2–155%. In normal amniotic fluid at 16–20 weeks of pregnancy, HCG concentrations were 3180± 2270 (755–11 000) mlU/ml with the FIA.