SMFM 27th Annual Meeting 2007
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read the abstract: The AmniSure® ROM Test is Superior to Conventional Clinical Assessment in the Diagnosis of Rupture of Membranes
Alix Boyle: Hi, this is Alix Boyle reporting from the OBGYN.net. We are here at the SMFM meeting in San Francisco. I am speaking today with Dr. Errol Norwitz from Yale University. He has done some research into ruptured membranes, what prompted you to do the research?
Errol R. Norwitz, MD, PhD: Well, as you know the membranes are integral to the maintenance of pregnancy. It’s a very thin membrane, only a few cells thick, but if the membranes rupture prematurely it allows ascending infection to get up through the vagina, into the cervix and then ultimately into the uterus and cause preterm labor and chorioamnionitis. So it is important that the membranes remain intact throughout the pregnancy. If the membranes rupture at the end of pregnancy, it’s not a big problem, you just deliver the baby. But if they rupture earlier it can be a major cause of preterm birth and the subsequent damage, neurological injury, and premature sequelae for the baby. So, the issue of ruptured membranes is a major problem that we, as high-risk obstetricians face clinically.
One would think it would be easy to make the diagnosis. In fact the traditional technique of making the diagnosis is to put a speculum into the vagina and look for leakage of fluid through the cervix, which we call pooling, looking for a ph change to an alkaline ph from an acid ph, which we test with Nitrozene paper and then drying out some of the discharge onto a slide and looking for a ferning pattern or crystallization of the amniotic fluid. Those are the three classic tests we do to look for ruptured membranes. And as I said, one would think that it would be an easy test to do to confirm ruptured membranes or not. The distinction is really important. If somebody doesn’t have ruptured membranes they go home. They might have been leaking vaginal discharge or perhaps a small leak of urine, but as long as the membranes are intact, and there is no amniotic fluid leaking, they can go home, and continue their pregnancy.
If they have ruptured their membranes and the pregnancy is still remote from term, then they really need to stay in hospital. They need to get antibiotics, potentially get steroid therapy, we typically get high-risk maternal fetal medicine involved, as well as neonatology, and they need to be delivered early. Typically we would deliver these patients at 34 to 35 weeks. Whether or not somebody who presents with leakage of vaginal fluid actually has ruptured her membranes or not is a very important distinction, and we have relied on these clinical tests that actually are not particularly reliable.
We chose to look at a commercial test that is being used quite commonly now in Europe. The test is called AmniSure and it looks for leakage of a protein called placenta alpha-macroglobulin one, or PAM G1, in the vaginal environment.
Alix Boyle: Interesting, what were the results of your research?
Errol R. Norwitz, MD, PhD: This was done in collaboration with a group in Korea. We took about 180 women who sequentially presented to labor and delivery with complaints of leakage of fluid and needed to be evaluated to look for ruptured membranes. What we did was the classic speculum examination and the three clinical tests, the pooling, ferning and Nitrozene, Then we did the AmniSure test, which essentially requires putting a small cotton or Dacron swab into the posterior fornix, collecting some of the cervical vaginal discharge, then eluting that into a buffer and using a testing strip to look for the presence or absence of this protein. The advantage of this test; it is much more objective, and also there is an enormous distinction between the concentration of this protein in the amniotic fluid, and the cervical vaginal discharge. The difference is about 1,000 to 10,000 fold, so that even a small leakage of amniotic fluid into the vagina will cause a large amount of this protein to be present.
The theoretic advantage is in clearly having an objective test rather than these much more subtle and subjective tests; it would be a distinct advantage. We were interested in seeing if indeed this was a better test than the standard, subjective clinical assessment that we now use to make the diagnosis. And indeed that was our observation, that this test was more sensitive and specific in confirming the diagnosis of ruptured membranes.
Alix Boyle: What will this mean for the future for pregnant women?
Errol R. Norwitz, MD, PhD: As I said earlier, this test is currently being used in Europe and several other countries; it will avoid cases of amniocentesis to confirm ruptured membrane. Occasionally people who are remote from term, if there is a major concern about the diagnosis and we can’t confirm it clinically, we end up doing an amniocentesis, instilling some dye into the amniotic fluid and then looking for leakage into the vagina. Obviously an invasive test like that carries with it some risk. If we could use this minimally invasive test it would really do away for the need for these amnio-dye infusions.
Alix Boyle: Would this ever be developed as a home test the patients could use themselves?
Errol R. Norwitz, MD, PhD: That’s an excellent question. Indeed it may. It’s been developed along the lines of the early pregnancy test. If indeed it becomes available, it might be something that women will be able to buy over the counter and use at home to confirm whether or not the leakage they’re experiencing is amniotic fluid, or just vaginal discharge or some leakage of urine. Down the line perhaps it would be available to people at home. It’s not currently how the test is being developed but that potential exists.
Alix Boyle: Interesting, thank you Dr. Norwitz.
Errol R. Norwitz, MD, PhD: Thank you.