AmniSure® Diagnostic Test for Rupture of Membranes
Richard Porreco, MD, Obstetrix Medical Group, Denver, CO and Andrew C. Combs, MD, PhD, Obstetrix Medical Group, San Jose, CA

Transcript

Richard Porreco, MD: Hi, my name is Rich Porreco; I am Director of Maternal Fetal Medicine at Presbyterian St. Luke’s Medical Center in Denver, Colorado. I am here with Andy Combs. Andy?

Andrew C. Combs, MD, PhD: Hi, I am a perinatologist with Obstetrix Medical Group and I am the Chairman of Ob/Gyn at Good Samaritan Hospital in San Jose. We are here today to talk about AmniSure®, which is an exciting new development in the diagnosis of rupture of membranes. The test is based on the appearance of placental-associated micro globulin protein which occurs only in amniotic fluid, so the test is very highly sensitive and specific for the diagnosis of ruptured membranes and also offers a number of other advantages.

Richard Porreco, MD: Well, it is important to make a diagnosis, don’t you think? Not only at term, it has impacted care every day in this country, but also pre-term when these fetuses are at high risk for problems and to miss the opportunity to know how the fetus is because of premature rupture of the membranes would be a disaster. So having a gold standard, if you will, an accurate test that is easily applied can make a big difference in care.

Andrew C. Combs, MD, PhD: That is absolutely right. Both false positives and false negatives are both a huge problem with clinical and economic consequences. Typically, traditionally in our specialty, we have had to put a speculum in and we have had to look for amniotic fluid issuing from the cervix, we have done a variety of bedside tests on it to make the diagnosis. It would be much more applicable and resource-friendly if we could get a test that was equally as sensitive or better for bedside nurses, experienced labor and delivery and bedside nurses or nurse practitioners or physicians to make the diagnosis without putting a speculum in. That is uncomfortable for the patients, to be sure, and I think that the advent of the technology to do that is really at hand.

Richard Porreco, MD: Absolutely.

Andrew C. Combs, MD, PhD: Our experience is that both at our hospital, which is a community level- three hospital, but also the neighboring hospitals in our community, the diagnosis of ruptured membranes oftentimes is the nurse placing a piece of nitrozene paper on whatever discharge is coming out and the fern test is oftentimes not even done as a confirmation. So we see a lot of false positives and false negatives. So the availability of a test that can be done by a nurse and doesn’t require the doctor to come and actually perform the test is huge.

Richard Porreco, MD: You know, the other thing is, we are a referral center from a relatively rural area and when a small rural hospital has a patient with pre-term rupture of the membranes or any question of it, they are quickly given incentive to try to move that patient to a tertiary center and sometimes the patients do not have ruptured membranes. They make a long trip, sometimes with adverse weather circumstances, and it would be really important if they could hang their hat on a test and say, you know, you really do not have ruptured membranes, you do not need to leave our community and be re-evaluated at a distance and at great expense. So the ease and applicability of this test for family practice doctors, certified nurse midwives, obstetricians who are in more rural settings, has a lot of impact in care and also resource allocation.

Andrew C. Combs, MD, PhD: In terms of accuracy, I know we both read the paper by Cousins in the American Journal of Perinatology that showed the test was as accurate as fern and nitrozene in combination and in a few cases where there was disagreement, the conclusion was that it was actually the AmniSure® that was correct rather than the fern and nitrozene test. But you have done a trial on your own confirming the accuracy.

Richard Porreco, MD: We have. We need a gold standard. What is the gold standard? I think in the abstract, it is here at the SMFM they use the longitudinal assessment of ruptured membranes as the gold standard and compare AmniSure® versus traditional methods. But a test a lot of folks around the country have relied on for many years is indigo carmine instilled at amniocentesis into the amniotic cavity and the egress of that blue dye in the next few hours, its appearance on a vaginal tampon, has been generally accepted as the gold standard. We have had occasion with our referral maternal fetal transport service to do amniocenteses on; I mean if they are grossly ruptured, whether it is at term or pre-term, this really is not an issue. It is the ones where there is a question, where you need to be certain, and we have done amniocenteses on those patients because we want to know about infection and other reasons that pre-term premature rupture of the membranes is so important a diagnosis to make. While we are there, if there is a question about the status of the membranes, we have dropped in 3 cc of indigo carmine and since we have had the availability of AmniSure®, in about 20 cases, we have also looked at AmniSure® and seeing whether it agrees with the egress of blue dye and so far, we have got 100% correlation. If the dye does not come out, the AmniSure® is negative and if the dye does comes out and indeed there is a rupture, the AmniSure® is positive.

Andrew C. Combs, MD, PhD: That has been my experience, as well, with the AmniSure® test. I have not had a single case where I was concerned about the accuracy of the test. Every time is has been used; it seems to give the correct result. So in summary, we have a very simple test to perform. The nurse can perform this test by placing the swab into the posterior fornix of the vagina and then the swab is developed in solution for a few minutes right at the bedside and the result is available immediately to the clinician. AmniSure® seems to have promise to become the next gold standard for the diagnosis of rupture of membranes.