Detection
Early pregnancy factor is tested for rosette inhibition assay. EPF is present in the maternal serum (blood plasma) shortly after fertilization; EPF is also present in cervical mucus and in amniotic fluid.
EPF may be detected in sheep within 72 hours of mating, in mice within 24 hours of mating, and in samples from media surrounding human embryos fertilized in vitro within 48 hours of fertilization (although another study failed to duplicate this finding for in vitro embryos). EPF has been detected as soon as within six hours of mating.
Because the rosette inhibition assay for EPF is indirect, substances that have similar effects may confound the test. Pig semen, like EPF, has been shown to inhibit rosette formation - the rosette inhibition test was positive for one day in sows mated with a vasectomized boar, but not in sows similarly stimulated without semen exposure. A number of studies in the years after the discovery of EPF were unable to reproduce the consistent detection of EPF in post-conception females, and the validity of the discovery experiments was questioned. However, progress in characterization of EPF has been made and its existence is well-accepted in the scientific community.
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