A NOVEL BIOASSAY FOR DETECTION OF PREIMPLANTATION FACTOR (PIF)

PROBLEM: To identify the presence of vital preimplantation embryos in vivo in humans, a newly observed phenomenon based on autorosette forma tion between lymphocytes and platelets, when treated with pregnant ser a, was used as a marker.METHOD: Serum samples were obtained from 65 pa tients on the fourth day after embryo transfer (ET). Sera from 10 heal thy males and 47 nonpregnant women were used as controls. The preimpla ntation factor (PIF) was detected by using blood group O+ donor lympho cytes and platelets incubated with blinded serum in the presence of an ti-CD2 antibody and rabbit complement. Human chorion gonadotropin (hCG ) concentrations were determined 7 days later and compared with result s of the lymphocyte-platelets assay. Implantation was confirmed by ult rasonographic evidence of presence of an intrauterine gestational sac. The role of platelet activating factor (PAF) in the observed phenomen a was studied experimentally. RESULTS: Significantly more lymphocyte-p latelet rosette formations were observed when sera from women who succ essfully implanted were compared to sera from women who failed to impl ant. This assay yielded a specificity of 95%, sensitivity of 88%, posi tive predictive value of 94%, and negative predictability of 90%. PAF added directly to the cell suspension and tested sera controls did not influence the percentage of lymphocyte/platelets rosettes. CONCLUSION : The application of PIF assay will enable the identification and stud y of early pregnancy events before the implantation occur. PAF by itse lf is not responsible for the rosette formation.