Author(s): Dorota Knapik, Anita Olejek
A diagnosis of premature rupture of membranes (PROM) is mainly based on the interview and physical examination. In a doubtful situation, various tests of cervico-vaginal secretions and ultrasound are used. At present, the most widely advertised and commercially produced tests of cervico-vaginal secretions are AmniSure® (based on the analysis of placental alpha-microglobulin-1, i.e. PAMG-1) and Actim Prom® (based on the analysis of type 1 insulin-like growth factor binding protein, i.e. IGFBP- 1). PAMG-1 is a protein present only in the amniotic fluid, whereas IGFBP-1 is a protein whose concentrations in the amniotic fluid largely exceed those in the plasma. Both markers have the potential to become a standard in the diagnosis of PROM. Concentrations of PAMG-1 range from 2,000 to 25,000 ng/ mL in the amniotic fluid and from 0.05 to 0.2 ng/mL in normal vaginal secretions. The manufacturer proposes a concentration of 5 ng/mL as the cut-off point, which seems to effectively prevent any false-negative results. The technology is not affected by the presence of blood and can be used at any gestational age. IGFBP-1 is a protein produced by the decidua and the fetal liver. Its concentration in the amniotic fluid is around 27 ng/mL shortly after conception and reaches a level above 100,000 ng/mL in advanced pregnancy; for comparison, the maternal plasma levels are fairly constant and range from 58 to 600 ng/mL. Having analyzed the data from the literature, it may be concluded that the mean sensitivity and specificity values for the test with IGFBP-1 (obtained by 7 different research groups) were 93.5% and 92.5%, respectively, while for the test with PAMG-1: 96.2% and 97.2%, respectively. Both tests have therefore sufficient parameters to fulfill the tasks set for them. The PAMG-1 test is superior due to the lower influence of blood in the sample.