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New AACC Guidance Advises Against Using Tests to Predict Premature Birth

NEW YORK – The American Association for Clinical Chemistry issued new guidance on Wednesday advising against the routine use of tests that claim they can predict premature births.

The organization recommends against using these tests in the routine evaluation of women with symptoms of preterm delivery. The tests usually measure fetal fibronectin, or fFN, interleukin 6, and placental alpha macroglobulin-1 to identify patients at risk of premature delivery, but no studies have "demonstrated definitive clinical value," the organization wrote in its guidance document.

AACC noted that "identification of women who will deliver preterm is critical to allow selective initiation of appropriate therapy, while preventing unnecessary treatment of women who will deliver at term," but added that "identifying individuals at risk of delivering prematurely is inherently challenging" because the best predictor of premature birth is a history of previous preterm delivery. Another challenge is the "ubiquitous nature of signs associated with the onset of labor," such as pelvic pressure or backache.

According to the guidance document, tests for these biomarkers have low positive predictive values, meaning many women who are identified as being likely to deliver prematurely won't actually give birth early. For example, "randomized controlled trials that assess patient outcomes and healthcare utilization by implementing fFN testing are lacking and existing studies have found conflicting results," the authors said.

The one exception to this recommendation is that in patients who present with symptoms of premature labor and who are at high risk of preterm delivery due to cervical length, a positive PAMG-1 result could help identify patients who are likely to deliver within a week. In patient populations with a higher prevalence of spontaneous preterm delivery within one week, PAMG-1 would likely "provide clinical value as the majority of women with a positive test result would go on to deliver prematurely."

The document also notes that many professional societies disagree about the utility of fFN for predicting preterm birth, recommending laboratory professionals and obstetricians discuss all available recommendations on preterm birth testing together and take a collaborative approach to developing institutional testing strategies for preterm birth.

The organization noted that one limitation of currently available tests is that they only measure a single protein, and multi-marker panels may improve performance. However, the multi-marker panels that have been evaluated so far "do not demonstrate improved diagnostic performance relative to single biomarkers."

One potential solution is to "limit biomarker testing to high-risk women, thereby increasing the pre-test probability of the population being tested and improving the [positive predictive value] of currently available test methods," the authors wrote. Another solution would be to identify "novel diagnostic tools with improved PPV to predict the minority of symptomatic women who will deliver prematurely," they added.