[Methodological study on magnetic enzymic immunoassay for detecting free hCGbeta subunit].

Aim: To establish a novel magnetic enzyme immunoassay (MEIA) for detecting human choriogonadotropin free beta subunit (hCGbeta).

Methods: Two monoclonal antibodies (mAb) were used for conjugating with FITC and with alkaline phosphatase(AP) respectively, which incorporated magnetic solid phase separation. Magnetic beads were coupled with sheep anti-FITC antibody as solid phase, and phenolphthalein monophosphate was used as substrate to set up MEIA for detecting hCGbeta.

Results: The sensitivity of hCGbeta MEIA kit reached 0.1 IU/L. The intraassay variation and inter-assay variation was 8.5% and 14% respectively, with the average recovery rate of dilution of 92.5%. The kit showed no cross reactivity to LH, TSH and FSH, while a cross reactivity of 1.2% to intact hCG at concentration of 1000 IU/L. The time of efficacy of hCGbeta MEIA kit was longer than 14 months.

Conclusion: hCGbeta MEIA kit is better than hCGbeta radio immunoassay and ELISA kit, which can provide a high-qualitative and cheap hCGbeta kit for market.