Pre-term Labour Markers

Pre-term Labour Markers

Preterm labour is defined as regular contractions of the uterus resulting in changes in the cervix that start before 37 weeks of pregnancy. 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.

NICE guideline on preterm labour and birth {NG25} states that women reporting symptoms of preterm labour who have intact membranes should have a clinical assessment. If transvaginal ultrasound measurement of cervical length is indicated but is not available or not acceptable, fFN testing should be considered to determine the likelihood of birth within 48 hours for women who are 30 weeks plus 0 days pregnant or more. If the fFN test result is negative (≤50 ng/mL), it is unlikely that the woman is in preterm labour. If fFN is positive (>50 ng/mL), preterm labour should be diagnosed and treatment offered.

NICE Diagnostic guidance [DG33] Biomarker tests to help diagnose preterm labour in women with intact membranes published in 2018 stated that there was insufficient evidence to recommend routine adoption of Actim Partus, Partosure or quantitative fFN (using thresholds other than 50 ng/mL to guide clinical management) to help diagnose preterm labour in women with intact membranes when transvaginal ultrasound measurement of cervical length is not available or not acceptable. Recommendations on fFN testing with a fixed threshold of 50 ng/mL are not affected by this diagnostics guidance.

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.

Actim Partus (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.

Weqas offers 2 EQA programmes, one for qualitative and quantitative fFn and a separate programme for phIGFBP-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.

Two samples are distributed bi-monthly, providing 12 samples over the year. The programme 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.

Key Features:

  • Liquid stable samples are supplied ready to use; no pre-analytical preparation is required.
  • Qualitative and Quantitative reporting available, with interpretations based on cut-offs of 50 ng/mL for fFn and 10 ug/L for phIGFBP-1.
  • Linear related panel distributed covering the clinically relevant range.
  • Programme assesses both site and device performance, including bias, within and between batch imprecision and linearity.
  • Scoring based on Milan Model 3 performance specification.

2 x 0.6mL
Synthetic Amniotic Fluid containing purified fFN and phIGFBP-1
Pre-term Labour Markers
ProgrammeAnalyteApprox. Range Covered
fFNQuantitative fFN0 - 400 ng/ml
fFNQualitative fFNNegative / Positive
phIGFBP-1phIGFBP-1Negative / Positive

Related Documents


UKAS Proficiency Testing 4301UKAS Calibration 4301

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