Placental Alpha Microglobulin-1 (PAMG-1) Protein
Placental alpha microglobulin-1 was isolated in 1975 from amniotic fluid by D. Petrunin and was originally referred to as specific alpha-1 globulin of placenta. Placental alpha microglobulin-1 (PAMG-1) is present in the blood, amniotic fluid and cervico-vaginal discharge of pregnant women.
The concentration is several thousand magnitudes higher than that which is found in vaginal discharge in pregnant women when the fetal membrane is intact.
PAMG-1 has been found to be present in amniotic fluid throughout all three trimesters of pregnancy.
"The vertical axis represents a spectrum of PAMG-1 concentrations while the horizontal axis represents various bodily fluids. The blue square to the far left demonstrates the level of PAMG-1 in vaginal discharge. This is a very small amount. The orange bar to far right represents the PAMG-1 levels in pure amniotic fluid. As can be seen, the concentration of PAMG-1 in amniotic fluid is several thousand magnitudes higher than it is in vaginal discharge. Note that there is no overlap in ranges. Similarly, the concentration of PAMG-1 in a typical vaginal sample of a ruptured patient, which is represented by the red bar, is above the background concentration. The threshold of AmniSure is represented by the vertical green rectangle and has at 5ng/ml. Even the tiniest leakage of amniotic fluid causes drastic increases of PAMG-1 protein levels in vaginal discharge, allowing AmniSure to detect subclinical or even silent ruptures above 5ng/ml. The reason why PAMG-1 concentration found in an actual sample can be lower than that found in amniotic fluid is because other fluid in the vagina may dilute the sample. The PAMG-1 concentrations in other substances, such as semen and urine (which are not shown), have been found to be below the threshold of AmniSure and therefore are not known to interfere with the test."
Petrunin DD, Griaznova IM, Petrunina IuA, Tatarinov IuS. Immunochemical identification of the human placenta organospecific alpha 2 globulin and its concentration in amniotic fluid. Moscow Medical Institute, USSR. Biull Eksp Biol Med 1976;82(7):803-804.