Pre-term Labour Markers
Pre-term Labour Markers
Purpose:
Preterm labour is defined as regular contractions of the uterus resulting in changes in the cervix that start before 37 weeks of pregnancy. Point of care (POC) biomarker tests PartoSure, Actim Partus and quantitative Rapid fetal fibronectin (fFN) are intended for use with other clinical information to assess the risk of preterm birth in women with symptoms of preterm labour who have intact amniotic membranes.
fFN is an adhesive glycoprotein that holds the membranes of the uterus to the fetal membranes. After 35 weeks of pregnancy, it begins to break down naturally, and is detectable in vaginal secretions. A positive result indicates an increased risk of pre-term labour and is useful in aiding patient management. The negative predictive value (NPV) of the test at 10 ng/mL is quoted as 100%, with a NPV at 50 ng/mL of 99.2%. The manufacturers quote a cut-off of >50 ng/mL as a positive result; indicating the likelihood of a preterm birth within the following 14 days. Further information is provided in NICE guideline on preterm labour and birth {NG25}
Phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) is a biochemical marker used as an aid in assessing the risk of preterm delivery in pregnant women with signs and symptoms of preterm labour and intact amniotic membranes, after 22 weeks plus 0 days of pregnancy. IGFBP-1 is present in amniotic fluid primarily as a non–phosphorylated form. The phosphorylated form is produced mainly by human decidual cells and is present between the chorion and decidua. As the cervix matures and labour approaches, the chorion and decidua detach and decidual proteins, including phIGFBP-1, leak into the cervical secretion. The test has a limit of detection of 10 ng/mL and a measuring range of 10 to 8,000 ng/mL. Actim® Partus is a POC test designed to detect phIGFBP-1.
Due to the discontinuation of the Hologic fFN test, in July 2024, NHS England issued the following statement:
It is recommended that women presenting in threatened preterm labour should be assessed with an alternative test (Actim® Partus):If this test is negative, the woman can be assumed to be at low risk of preterm birth and as such would not require in-utero transfer or optimisation medications. If the test is positive, the woman should be recommended to deliver in an appropriate unit and receive optimisation medications.
Placental alpha microglobulin‑1 (PAMG‑1) is a protein released from the lining of the uterus into the amniotic cavity throughout pregnancy. It is found in very high concentrations in amniotic fluid and in very low concentrations in normal vaginal discharge. Studies have demonstrated a strong correlation between the presence of PAMG‑1 in cervicovaginal discharge and imminent delivery. PartoSure is a qualitative lateral flow, immunochromatographic POC test designed to detect (PAMG‑1) in vaginal secretions during pregnancy. The test has a limit of detection of 1 ng/ml and a measuring range of 1 to 40,000 ng/ml.
Scope:
Weqas offers 3 separate programmes, one for qualitative and quantitative fFn and separate programmes for phIGFBP-1 and PAMG-1. Purified human fFN and semi – purified IGFBP-1 are added to an artificial amniotic fluid buffer base containing anti-proteases, detergents, proteins and preservatives to produce high positive samples. The two high positive samples are further diluted with the negative base to create a series of samples spanning the analytical range. Each of the samples are distributed on 2-3 occasions to allow for the assessment of between batch variability. For PAMG-1, material is sourced from a third supplier and currently not produced in house.
Two samples are distributed bi-monthly, providing 12 samples over the year. The programmes assesses both site and device performance, including bias, within and between batch imprecision for the quantitative analytes. Challenging samples are distributed at or near the limit of detection and diagnostic thresholds for the qualitative analytes.
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Key Features:
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Frequency: Bimonthly |
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Samples: 2 x 1.0ml for phIGFBP-1, 2 x 0.5mL for fFN and PAMG-1 |
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Material: Synthetic Amniotic Fluid containing purified fFN, phIGFBP-1 or PAMG-1 |
| Pre-term Labour Markers | ||
|---|---|---|
| Programme | Analyte | Approx. Range Covered |
| fFN | Quantitative fFN | 0 - 400 ng/ml |
| fFN | Qualitative fFN | Negative / Positive |
| phIGFBP-1 | phIGFBP-1 | Negative / Positive |
| *PAMG-1 | PAMG-1 | Negative / Positive |
* Pilot programme for 2025. Currently not accredited.
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