Performance Data

AmniSure® is a one-step immunochromatographic assay. Three monoclonal antibodies are used in the test to detect PAMG-1. AmniSure® works within a wide range of PAMG-1 concentrations in vaginal secretion (from 5 ng/ml to 100 mcg/ml). The diagnostic accuracy of the test relies on only a miniscule amount of released amniotic fluid.

In clinical studies, patients were evaluated by “clinical assessment"-control and by the AmniSure® device. Clinical assessment-control involved setting a diagnosis using a combination of the routinely used Nitrazine, Ferning and Pooling tests. The diagnosis was established when at least two out of three control tests produced identical results (2-out-of-3 method). Estimation of Binomial Parameter (PI) - the positive and negative agreements between the AmniSure® test and classic control - were estimated as follows:

Test Characteristics

• Positive Agreement = 97.2% (69/71) with 95% Confidence Interval
  CI =(90.2%, 99.7%)
  
• Negative Agreement = 97.6% (81/83) with 95% Confidence Interval
  CI = (91.6%, 99.7%)

The AmniSure® test employs highly sensitive and specific proprietary monoclonal antibodies (MAB) that detect even a minimum amount of the amniotic fluid protein, Placental Alpha Microglobulin-1 (PAMG-1). PAMG-1 was discovered by N-Dia's team in 1975. Amniotic fluid containing PAMG-1 is present in cervico-vaginal secretions after the rupture of fetal membranes. To minimize the frequency of the false results, the pair of MABs (A and B) has been specifically selected to recognize the small background fraction (0.2 ng/ml) of PAMG-1 molecules in the vaginal secretion of a pregnant woman. Third MAB (C) against PAMG-1 (not shown in the CHART) is used to set the sensitivity threshold of AmniSure® at the optimal low level. This level allows the detection of the extremely small quantities of amniotic fluid (0.05-0.005 of a drop) in vaginal secretions.

As a first step of the test, the vaginal swab is used non-invasively to take a sample of vaginal secretion. The swab is then dipped into a vial with solvent that extracts the sample substance from the swab. Finally, the test strip is dipped into a vial and result is read after 5-10 min.

The Pad Region of the test strip is dipped into the vial CHART). A-MABs in soluble form are located in the Pad Region. These MABs have colloidal gold particles attached to them. When A-antibodies come in contact with PAMG-1 protein, resulting from the rupture of fetal membrane and the subsequent leakage of the amniotic fluid, they “catch” PAMG-1 and transport it to the test region.

The test region of the test strip has B-antibodies immobilized on it. B-antibodies “meet” PAMG-1 bound to A-MABs flowing up from the Pad Region. This “meeting” immobilizes the system of PAMG-1/A-MABs, resulting in a brown/yellow stripe that becomes visible in the test region. This stripe is produced by gold dye attached to A-antibodies and indicates a rupture of fetal membranes.

The second stripe, the one in the control region, has nothing to do with fetal membrane rupture. It is designed to provide indication that the test strip is functioning properly. This stripe appears when rabbit anti-mouse IgG antibody (not shown in the CHART) catches the mouse A-antibody with dye gold. Gold dye gives the resulting stripe its color.