**8.3 Present tests of today**

#### **DAO test (DiAmine oxidase activity)**

The DAO test was one of the first biochemical tests for PROM, and was developed during the 1970's. DAO is present in high concentrations in AF but is absent in normal vaginal secretions and urine. DAO is produced by placental decidual cells and increases during pregnancy. The method is reported to have a sensitivity of 84-100% and a specificity of 74- 100%. The test was carried out with 10 ul of AF absorbed on a paper strip, and the test requires a scintillation counter. This method is not available today because of the toxic chemicals that are used in the analysis.

#### **AFP test (Monoclonal antibody test kit)**

AF also contains high concentrations of alpha feto protein (AFP) especially in preterm pregnancy. A monoclonal antibody assay method with high sensitivity and specificity was presented. However, they also reported that a false positive test may occur as AFP may cross weakened membranes in cases with chorioamnionitis or heavy blood contamination. This test is not used in clinical practice any more.

#### **Fetal fibronectin (ROM-check)**

234 From Preconception to Postpartum

Fig. 4. Photo taken at microscopy (x 40) of AF from one woman included in the "lac-test" study.

Nile blue sulphate staining of the neutral lipid in cells from fetal sebaceous glands was described in 1960's. The cells turn orange as a consequence of the oxazone in Nile blue. The cells are single or grouped in clusters. Other cells, like vaginal squamous, and pus cells or erythrocytes stain blue. A limitation of this test is that these fat-containing cells are only

In selecting a spectrum of tests to be used in doubtful instances of ruptured membranes, it was determined that a combination of these three tests described above would produce an

The DAO test was one of the first biochemical tests for PROM, and was developed during the 1970's. DAO is present in high concentrations in AF but is absent in normal vaginal secretions and urine. DAO is produced by placental decidual cells and increases during pregnancy. The method is reported to have a sensitivity of 84-100% and a specificity of 74- 100%. The test was carried out with 10 ul of AF absorbed on a paper strip, and the test requires a scintillation counter. This method is not available today because of the toxic

AF also contains high concentrations of alpha feto protein (AFP) especially in preterm pregnancy. A monoclonal antibody assay method with high sensitivity and specificity was presented. However, they also reported that a false positive test may occur as AFP may cross weakened membranes in cases with chorioamnionitis or heavy blood contamination.

present after 32 weeks of gestation.

**8.3 Present tests of today** 

accuracy of diagnosis approximating 93%.

**DAO test (DiAmine oxidase activity)** 

chemicals that are used in the analysis. **AFP test (Monoclonal antibody test kit)** 

This test is not used in clinical practice any more.

Fibronectin is a large plasma glycoprotein. Three sub-types are available, of which one is feta derived. The concentration of fetal fibronectin in amniotic fluid is 5-10 times higher than in maternal plasma. In the 1990's many papers were published about fetal fibronectin and its usefulness to detect AF in women with suspect PROM. To use fetal fibronectin when detecting PROM is a sensitive test (97%) but a test with a very low specificity (27%). Additionally, in patients without rupture of the membranes, the interval between sampling and delivery was shown to be significantly shorter if fetal fibronectin was present. The conclusion was that the presence of fetal fibronectin in cervicovaginal secretions may be a good marker for impending labor rather than a good test for ruptured membranes. Today fetal Fibronectin is used in a combination with ultrasound, to detect the risk of premature delivery.

#### **Insulin-like growth factor binding protein-1 (PROM-test™)**

Insulin-like growth factor (IGF) is a peptide and is bound to a binding protein (IGFBP) in the blood circulation. IGFBP-1 is a placental protein and is present in much higher concentrations in AF as compared with serum, cervical mucous, urine or seminal plasma. A commercial kit, with monoclonal antibodies to IGFBP-1 attached to a small wand has been available since 1993 (actim PROM-test™). During the last decade, many papers have been published on the actim PROM-Test™. The sensitivity of the test is reported to be 71-100% and specificity 88-100%. It has been concluded that actim PROM-test™ is one of the most accurate diagnostic tests today in the diagnosis of suspected PROM. However, contamination of maternal blood or leakage of IGFBP-1 through stretched fetal membranes may cause false positive tests. A false negative result may occur if there is an inadequate sampling, intraamniotic infection, vaginal discharge, maternal blood loss, or prolonged time from rupture of membranes to application of the test. Gestatational age should not influence the test. intraamniotic

#### **B-HCG in vaginal washing fluid**

B-HCG is a glycoprotein produced exclusively by syncytiotrophoblasts in the placenta. Several studies have investigated β-HCG as a useful test for the diagnosis of PROM in the third trimester. These studies have shown a sensitivity of 68-100% and a specificity of 95-97%.

#### **Amnisure®**

In 1975, the placental alpha microglobulin–1 (PAMG-1) protein was isolated from AF. Antibodies were obtained against the protein and Amnisure® is an immunochemical method, used to measure the content of PAMG-1 protein in vaginal fluid, in cases with suspect PROM. Amnisure® has been available on the market since 2005. In a study which included 203 women with suspected PROM, a sensitivity of 98.8% and a specificity of 100% were found.
