Scheme Information Sheets
Maternal Serum Screening First Trimester
For information regarding Maternal Serum Screening Second Trimester and NTD, click here.
| Scheme Particulars | Indicative Details |
|---|---|
| Accreditation body | UKAS |
| ISO/IEC Accreditation status | ISO/IEC 17043:2023 |
| UKAS Accredited Proficiency Testing Provider No | 7860 |
| Objective of Scheme | Provides EQA coverage for biochemical Maternal Serum Screening in the First Trimester using free-beta hCG and Pregnancy Associated Plasma Protein A (PAPP-A) plus demographic information (including gestational age and nuchal translucency measurement). Specimens cover a range of concentrations, plus Multiple of the Median (MoM) calculations, and chance of the pregnancy being affected by T21 or T18/13 that would be report based on the MoMs. Specimens will be targeted to cover the concentration ranges of the markers and probe some of the demographic impacts on the MoM and chance calculations |
| Pre-, Analytical, Post- status | Analytical and Post-Analytical |
| Number of distributions per year (nominal) | 11 |
| Specimens per distribution | 3 |
| Number of Specimens per annum | 33 |
| Frequency of distribution | Monthly |
| Scoring system | ABC |
| Material distributed | Pooled, liquid human serum with or without exogenous added analyte |
| Programme Director(s) / Organiser(s) | Rachel Marrington |
| Criteria for participation | All, but overseas by courier |
| Nominal sample volume (mL) | 1 |
| Sample presentation TACs | All analytes in the same tube |
| Data in Chemistry on-line Dashboard | Yes |
| Analyte | Approx Range | Default Units | Target Value | B Score Limit (%) | C Score Limit (%) |
|---|---|---|---|---|---|
| free hCG Beta | 0 – 150 | U/L | ALTM | 20.0 | 20.0 |
| free hCG Beta MoMs | 0 – 4 | ~ | ALTM | 20.0 | 20.0 |
| PAPP-A | 0 – 10 | U/L | ALTM | 20.0 | 20.0 |
| PAPP-A MoMs | 0 – 4 | ~ | ALTM | 20.0 | 20.0 |
| Abbreviation | Expansion |
|---|---|
| ALTM | All Laboratory Trimmed Mean |
| GLTM | Group Laboratory Trimmed Mean – which is the Method Principle Mean |
| MLTM | Method Laboratory Trimmed Mean – usually a manufacturer system / analyser mean |
| XALTM | An external value that may be from a Reference Method System |
| OGLTM | A Method Principle Mean used as the target for all laboratories |
| OMLTM | A specific Method Mean used as a target for all laboratories |
| OMMED | A Method Median used as the target for all laboratories |
| MED | Median |
Yes, MoMs will be available to be reported for all analytes.
Yes, 'Chance' will be available to be reported for each Scheme. 'Chance' is now more commonly used instead of 'Risk' in maternal serum screening because it more clearly communicates that the result is an estimate of probability, not a diagnosis, and avoids the negative connotations that 'risk' may carry for patients. We will also allow you to report Actions taken.
We plan to develop the Scheme to use different patient demographics to probe the programming of software used.
