Alpha Fetoprotein and Biomarker Testing for PROM
Testing for premature rupture of the amniotic membrane (PROM) during pregnancy is typically done via a sterile speculum exam, combined with clinical suspicion and patient history. The presence of amniotic fluid pooling from the cervical os is often confirmed by nitrazine testing or ultrasound. While it allows for a confident diagnosis, in many cases, it is not a useful indicator in the 47% of PROM occurrences which present no obvious leakage. 1
In terms of accuracy, the current gold standard for PROM testing is a dye infusion administered via amniocenteses. However, because of the expense involved and the invasive nature of the procedure, it is rarely performed.
Origins of Biomarker Testing
The search for an accurate biomarker for PROM dates back to the mid-1970s. One of the most prevalent proteins in amniotic fluid, alpha fetoprotein, was identified early on as a potential candidate.
However, studies concluded that alpha fetoprotein in amniotic fluid was “not [a] useful marker[…] for PROM because of the overlap in concentrations between women with and without ruptured membranes.” The test itself also did not demonstrate “sufficient sensitivity and specificity to justify routine use for detection of rupture of membranes.” For these reasons, AFP testing for PROM has fallen out of favor, replaced by the more accurate and effective diagnostic tools that have been developed in the past 10 years.
Newer Alternatives to AFP Testing for PROM
In recent years, several biomarkers have emerged as alternatives to speculum examination and testing for alpha fetoprotein in amniotic fluid. Testing kits for insulin-like growth factor-binding protein (IGFBP-1). Though they are easier to administer when compared to traditional ROM diagnostic methods, their specificity and sensitivity have suffered in clinical trials.
AmniSure® is the newest and most accurate form of biomarker testing for PROM currently available. AmniSure® tests for the presence of the protein PAMG-1, which is not present in significant background concentrations in the vaginal discharge. When compared to IGFBP-1, “the PAMG-1 test was found to be more sensitive […] in detecting amniotic fluid at lower concentrations in vitro.”4 The AmniSure ROM test has also been shown to be more effective when used in the presence of blood than IGFBP-1 based tests in the absence of blood.
- Neil PRL, Wallace EM. Is AmniSure® useful in the management of women with prelabour rupture of the membranes? Australian and New Zealand Journal of Obstetrics and Gynaecology 2010.
- Buyukbayrak EE et al. Diagnostic power of the vaginal washing-fluid prolactin assay as an alternative method for the diagnosis of premature rupture of membranes. J Matern Fetal Neonatal Med 2004; 15: 120–125.
- Shahin M, Raslan H. Comparative study of three amniotic fluid markers in premature rupture of membranes: prolactin, beta subunit of human chorionic gonadotropin and alpha-fetoprotein. Gynecol Obstet Invest. 2007;63:195–9.
- Albayrak M et al. Comparison of the diagnostic efficacy of the two rapid bedside immunoassays and combined clinical conventional diagnosis in prelabour rupture of membranes. Eur. J. Obstet. Gynecol. and Reprod. Biol. 2011;10