Development and evaluation of time-resolved fluoroimmunoassay kit for maternal serum free human chorionic gonadoatropin β subunit

Objective: To promote the development of the prenatal screening, and to develop a time-resolved fluoroimmunoassay (TRFIA) for maternal serum free human chorionic gonadotropin β subunit (free hCG β) as an aid in prenatal screening, and to prepare its test reagent. Methods: Solid-phase sand-wich TRFIA was used for quantification of free hCG β, which involved two anti-free hCG β monoclonal antibodies (McAb). One anti-free hCG β McAh was coated on microplates, the other was labeled by Europium. The main component of enhancement solution was 2-naphthalene trifluoroacetone. The assay methodolo-gy was evaluated. Linear regression analysis and paired samples t-test were used. Results: The correlation coefficient (r) of self-made kit dose-response curve reached 0.9990. The intra-assay and inter-assay coeffi-cient of variation (CV) was lower than 10.00%. The relative bias measured values of kit standard were lower than 5.00% difference from their labeled values. The sensitivity was better than 0.20 ng/ml. The ra-tio of self-made kit standard measured value over national standard value was 0.900 ∼ 1.100. There was lit-tle cross-reaction with human thyroid stimulating hormone (hTSH), human luteinizing hormone (hLH), human follicle stimulating hormone (hFSH), and hCG. The linear range was 2.00 to 200 ng/ml. Com-pared with imported kit, y = x + 0.0565, r=0.9771, and the results showed no statistical significance (paired samples t-test, t =0.1839, P >0.05). The values of self-made kit tested by self-made equipment and imported equipment showed no difference (paired samples t-test, t=-0.9669, P > 0.05), y=0.9894x + 0.0957, r=0.9995. The results of external quality assessment achieved 100%. EDTA-K2 (≥ 0.54 mmol/L), sodium citrate (≥1.06 mmol/L), K2C2O4H2O (≥2.12 mmol/L) or NaF (≥29.76 mmoL/L) in the tested samples had interference in the assay (interference > 10%). Sodium heparin (≤ 150 U/L),haemoglobin (≤12 g/L), triglyceride (≤21.54 mmol/L) or bilirubin (≤818 μmol/L) in the tested samples had no significant interference in the assay (interference < 10%). The results of samples would be ascended due to the instability of hCG if the temperature was elevated. Conclusion: The quality of self-made kit was in keeping with imported kit. (authors)