Laboratory tests are not perfect. I hope this does not come to a surprise to anyone. In a perfect world, a lab test would always identify individuals with a specific condition from those who don’t have that condition. Unfortunately, we don’t live in that world and so lab test results must be interpreted beyond the “negative” or “positive” result or any other way in which a lab test result is reported. Human beings and their health and disease states are complicated and few lab tests can lump people into binary buckets of “yes” or “no.” That’s precisely true for tests of ruptured membranes that might be used during the course of a woman’s pregnancy.

We’ve written about tests for ruptured membranes before here and here. Rupture of membranes (ROM) is the term used to describe the breaking of the amniotic sac, as normally occurs before the onset of labor. If this happens earlier than the 37thweek of pregnancy it is called preterm ROM (PROM).

It’s important to detect women with ruptured membranes, particularly women with PROM, because PROM can lead to complications such as intrauterine infection, umbilical cord compression, and premature birth. Fortunately, there are tests to help identify pregnant women with ROM or PROM. The more reliable of these tests detect substances in amniotic fluid; and amniotic fluid is not normally present in vaginal fluid samples obtained from women with intact membranes. If these substances are detected, then it’s possible the fetal membranes have ruptured. But these tests are not foolproof!

The U.S. FDA recently issued a “letter to healthcare providers” about the risks associate with the use of tests for ruptured membranes. In this letter, FDA reminds providers that over-reliance on tests for ruptured membranes can lead to serious, adverse events. Note the “over-reliance” comment. It echoes what I state above, that lab test results are not perfect tests. FDA confirms that“ 13 fetal deaths and multiple reports of health complications in pregnant women” have been reported because of over-reliance on the accuracy of ruptured membrane tests. In this letter, FDA reminds providers that tests of ruptured membranes should be “part of an overall clinical assessment,”which usually includes physical examinationof the patient as well as tests to detect leaking amniotic fluid.

As laboratory professionals, it is incumbent upon us to continually stress the strengths and limitationsof the tests that are performed in our labs every day.

Originally published by The Pregnancy Lab

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