Fetal anomaly screening standards valid for data collected from 1 April 2018
Updated 8 October 2024
Applies to England
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This publication is available at https://www.gov.uk/government/publications/fetal-anomaly-screening-programme-standards/standards-valid-from-1-april-2018
FASP-S01: coverage: T21, T18, T13 screening
Description
The proportion of pregnant women eligible for first trimester combined screening for Down’s syndrome (T21), Edwards’ syndrome (T18) and Patau’s syndrome (T13) for whom a conclusive screening result is available at the day of report.
Rationale
This standard provides assurance that screening is offered to everyone who is eligible and each individual who chooses to accept screening has a conclusive screening result.
Definition
We collect data on eligible women, tested women and women who decline screening as defined below.
The eligibility criteria for entry into the first trimester screening programme is a fetal crown rump length (CRL) measurement between 45.0mm and 84.0mm (11 weeks plus 2 days to 14 weeks plus 1 day of pregnancy).
Eligible women is the total number of pregnant women booked for antenatal care during the reporting period, excluding women who:
- miscarry between booking and testing
- opt for termination between booking and testing
- transfer out between booking and testing (do not have a result)
- transfer in before or at 14 weeks plus 1 day of pregnancy (CRL less than or equal to 84.0mm) who have a result from a screening test performed elsewhere in the NHS in this pregnancy
- have had private screening and do not wish to have NHS screening
- present to ultrasound between at or after 11 weeks plus 2 days and before or at 14 weeks plus 1 day (CRL 45.0mm to 84.0mm) weeks where it was not technically possible to measure the nuchal translucency (NT)
- present to service at or after 14 weeks plus 2 days (CRL greater than 84.0mm)
- have pregnancies of a higher order than twins (for example triplets)
- have a vanished twin where ultrasound shows there is a second sac containing a non-viable fetus
Tested women is the total number of eligible women for whom a completed screening result was available from the first trimester (T21 and or T18 and T13) screening on the day of report.
Ultrasound departments may not always have the capacity to accommodate women presenting later in pregnancy and we have allowed leeway of 1 week. Therefore, if you are not able to offer the combined test to women presenting to service between at or after 13 weeks plus 1 day and before or at 14 weeks plus 1 day they can be excluded. If you were able to offer these women the combined test they should be included.
Women who decline is the total number of eligible women who are offered screening and make an informed choice not to take up screening. Clear reporting of women who decline screening is required.
Performance thresholds
Thresholds are not set for this standard. FASP supports informed choice for women. This standard supports the safety of the screening pathway by enabling screening services to be assured that:
- all eligible women are offered the opportunity of screening
- women complete the screening pathway where the offer is accepted
Caveats
This requires matched cohort data and follow-up of any missed women.
Women should not be excluded but should be accounted for in the commentary if:
- there is a fetus where a serious fetal anomaly is suspected or identified at first scan that requires onward referral (such as anencephaly)
- the NT is measured as greater than or equal to 3.5mm and the woman declines blood sampling for biochemical testing before referral for clinical assessment (FASP recommends biochemical testing should be completed where screening is accepted)
Data collection and reporting
Data source: maternity service, ultrasound department and screening laboratory
Responsible for data quality and completeness: maternity service
Responsible for submission: maternity service
Reported by: maternity service
Published by: England, there is no intention to publish this standard/KPI by individual maternity service
This standard is also the key performance indicator FA3
Reporting period
Quarterly: data to be collated between 2 and 3 months after each quarter end
Deadlines: 30 September (Q1), 31 December (Q2), 31 March (Q3), 30 June (Q4)
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018
FASP-S02: coverage: fetal anomaly ultrasound
Description
The proportion of pregnant women eligible for fetal anomaly ultrasound screening who are tested leading to a conclusive result within the defined timescale.
Rationale
This standard provides assurance that screening is offered to everyone who is eligible and each individual who chooses to accept screening has a conclusive screening result.
The optimal gestational window for completing the fetal anomaly ultrasound scan is 18 weeks plus 0 days to 20 weeks plus 6 days of pregnancy.
The scan can be completed up to 23 weeks plus 0 days for women in the following circumstances.
-
For women who start screening between 8 weeks plus 0 days and 20 weeks plus 6 days and require a single further scan to complete screening where the image quality of the first scan is compromised by increased maternal body mass index (BMI), uterine fibroids, abdominal scarring or sub-optimal fetal position.
-
Where providers can arrange the fetal anomaly scan later within the recommended window and have a pathway to facilitate referrals for further investigations and options for pregnancy choices in a timely manner and within the required national timeframes. Ongoing audit of practice should be in place to monitor conformity. The screening pathway must be completed by 23 weeks plus 0 days.
-
For women who present to service at at or after 20 weeks plus 6 days where the sonography department can offer a screening scan appointment and complete screening by 23 weeks plus 0 days.
Definition
Numerator: tested women is the total number of eligible women for whom a completed screening result was available from the 18 weeks plus 0 days to 23 weeks plus 0 days week fetal anomaly scan at the day of report.
Denominator: eligible women is the total number of pregnant women booked for antenatal care during the reporting period, excluding women who:
- present to service at or after 23 weeks plus 1 day (as they are not part of the eligible population for the screening programme)
- miscarry between booking and testing
- opt for termination between booking and testing
- transfer out between booking and testing (do not have a result)
- transfer in at before or at 23 weeks plus 1 day of pregnancy who have a result from a screening test performed elsewhere in the NHS in this pregnancy
- have had private screening and do not wish to have NHS screening
- are offered an appointment within the optimal gestational screening timeframe but choose to attend at a different time for personal reasons
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
Ultrasound departments may not always have the capacity to accommodate women presenting later in pregnancy and we have allowed leeway of 1 week. Therefore, if you are not able to offer and complete the fetal anomaly scan to women presenting to service between at or after 22 weeks plus 0 days and before or at 23 weeks plus 0 days they can be excluded. If you were able to offer these women the fetal anomaly scan they should be included in the denominator.
Performance thresholds
Acceptable level: greater than or equal to 90.0%
Achievable level: greater than or equal to 95.0%
Caveats
This requires matched cohort data and follow-up of any missed women.
Data collection and reporting
Data source: maternity service and ultrasound department
Responsible for data quality and completeness: maternity service
Responsible for submission: maternity service
Reported by: maternity service
Published by: maternity service
This standard is also the key performance indicator FA2
Reporting period
Data to be collated quarterly, 2 quarters in arrears. Due to the potential lag time between early booking and ultrasound scanning, the complete cohort cannot be accounted for until 2 quarters later.
Deadlines: 31 December (Q1), 31 March (Q2), 30 June (Q3), 30 September (Q4)
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018
FASP-S03a: test: screen positive rate T21, T18, T13 screening
Description
Test performance - screen positive rate (SPR).
Rationale
This standard provides assurance that the screen positive rate for the national programme remains within the defined range to minimise the number of women requiring an offer of an invasive diagnostic test.
Definition
Numerator: number of screening tests with results above the cut off
Denominator: total number of screening tests in the reporting period
This standard measures test performance in singleton pregnancies only.
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
FASP defines the national cut-off set at 1 in 150 at term for both first and second trimester screening tests. A woman with a result of 1 in 150 or greater (between 1 in 2 and 1 in 150), of having a pregnancy with T21, T18, T13 in the first trimester, or T21 only in the second trimester, is considered to be in the ‘higher chance’ group and offered an invasive diagnostic test.
For women having screening using the combined test, dependent of their screening choice, up to 2 results are reported:
- a result for T21 and a result for T18 and T13
- a result for T21 only or T18 and T13 only
This standard excludes results based on increased NT measurement only. FASP recommends all women who make an informed choice to accept screening must have all components of the screening test completed - NT and biochemistry.
Performance thresholds
| Screening strategy | Trisomy | Acceptable standardised SPR | Achievable standardised SPR |
|---|---|---|---|
| Combined | T21 | 1.8 to 2.5% | 1.9 to 2.4% |
| Combined | T18 and T13 | 0.1 to 0.2% | 0.13 to 0.17% |
| Combined | T21, T18, T13 | 1.8 to 2.5% | 1.9 to 2.4% |
| Quadruple | T21 | 2.5 to 3.5% | 2.7 to 3.3% |
Both crude and maternal age standardised screen positive rates (SPRs) are reported. Ranges as specified reflect the need to maintain the SPR close to the national programme target. A SPR below the range may be associated with a lower than expected detection rate. A SPR above the range may be associated with a higher invasive testing rate.
Caveats
None
Data collection and reporting
Data source: screening laboratories
Responsible for data quality and completeness: screening laboratories
Responsible for submission: Down’s syndrome quality assurance support service (DQASS)
Reported by: England
Published by: England
Reporting period
Annually by June 30
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018
FASP-S03b: test: detection rate T21, T18, T13 screening
Description
Test performance - detection rate (DR)
Rationale
This standard monitors the true detection of the screening tests. This standard provides assurance that the screening tests are performing at optimal levels.
Definition
Down’s syndrome (T21) combined test
Numerator: number of confirmed cytogenetic diagnoses of T21 following a higher chance T21 result from the combined test
Denominator: number of confirmed cytogenetic diagnoses of T21 following any result (higher or lower chance) from the combined test
Edwards’ syndrome/Patau’s syndrome (T18/T13) combined test
Numerator: number of confirmed cytogenetic diagnoses of T18 and T13 following a higher chance T18 and T13 result from the combined test
Denominator: number of confirmed cytogenetic diagnoses of T18 and T13 following any result (higher or lower chance) from the combined test
T21, T18, T13 combined test
Numerator: number of confirmed cytogenetic diagnoses of T21, T18, T13 following a higher chance T21, T18, T13 result from the combined test
Denominator: number of confirmed cytogenetic diagnoses of T21, T18, T13 following any result (higher or lower chance) from the combined test
Down’s syndrome (T21) quadruple test
Numerator: number of confirmed cytogenetic diagnoses of T21 following a higher chance T21 result from the quadruple test
Denominator: number of confirmed cytogenetic diagnoses of T21 following any result (higher or lower chance) from the quadruple test
This standard includes:
- singleton pregnancies only
- screening tests that are part of the NHS screening programme
- antenatal and postnatal confirmed cytogenetic diagnoses of T21, T18, T13 where antenatal screening is completed as part of the NHS screening programme
This standard excludes:
- private screening tests
- results based on increased NT measurement only (FASP recommends all women who accept the offer of first trimester screening must have all components of the screening test completed - NT and biochemistry)
Both crude and maternal age standardised DRs will be presented. Ranges as specified reflect the need to maintain the DR close to the national programme target.
Performance thresholds
| Screening strategy | Thresholds |
|---|---|
| T21 (combined) | standardised DR 85.0% |
| T18 and T13 (combined) | standardised DR 80.0% |
| T21, T18, T13 (combined) | standardised DR 80.0% |
| T21 (quadruple) | standardised DR 80.0% |
DRs reported by the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS) are not modelled and are true DRs for confirmed diagnoses of Down’s syndrome, Edwards’ syndrome or Patau’s syndrome following participation in the FASP screening pathway.
Caveats
None
Data collection and reporting
Data source: screening and diagnostic laboratories
Responsible for data quality and completeness: screening and diagnostic laboratories
Responsible for submission: NCARDRS
Reported by: England
Published by: England
Reporting period
Annually by 30 June
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018
FASP-S04: test: fetal anomaly ultrasound
Description
Test performance - detection rate (DR) for specified serious cardiac anomalies.
Rationale
This standard is needed to monitor the performance of the screening strategy.
Definition
Numerator: identified babies with a cardiac anomaly found on the fetal anomaly scan
Denominator: identified babies from the screen population
The numerator and denominator include those completing a fetal anomaly scan between 18 weeks plus 0 days to 23 weeks plus 0 days.
The numerator and denominator exclude congenitally corrected transposition of the great arteries (TGA).
Identified babies are those with a confirmed diagnosis of one or more of the following serious cardiac anomalies occurring in isolation:
- TGA
- atrioventricular septal defect (AVSD)
- tetralogy of fallot (TOF)
- hypoplastic left heart syndrome (HLHS)
Performance thresholds
Acceptable level: DR greater than or equal to 50.0% for each serious cardiac anomaly listed above.
Caveats
Data is reported at least one year in arrears to allow for active postnatal ascertainment of cardiac anomalies, which are more likely to be screen negative.
The use of isolated anomalies reduces the bias possible by variation in the presences of co-existing non-cardiac anomalies which improve detection rates.
Data collection and reporting
Data source: maternity services
Responsible for data quality and completeness: maternity services
Responsible for submission: NCARDRS
Reported by: England
Published by: England
Providers are responsible for reporting identified babies born in their service and those diagnosed or screened in their service (if born elsewhere).
All identified babies must be notified by providers to NCARDRS as are other structural and chromosomal anomalies. Data items on dates and cardiac findings of fetal anomaly scans, repeat scans, expected date of delivery, date of booking to be completed or validated by relevant service of booking or screening.
Detection rates will be reported separately for each of the 4 cardiac anomalies.
Reporting period
Annually by 30 June
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018
FASP-S05: test: turnaround time T21, T18, T13 screening
Description
Screening test turnaround time
Rationale
This standard is needed to monitor the performance of the screening strategy.
Definition
Numerator: number of screening results reported within 3 working days of sample receipt
Denominator: total number of T21, T18, T13 screening samples received in the screening laboratory in the reporting period
Date of sample receipt in the laboratory is counted as day 1.
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
Performance thresholds
Acceptable level: greater than or equal to 97.0%
Achievable level: greater than or equal to 99.0%
Caveats
Denominator excludes initial samples received that are not fit for analysis and a repeat sample is requested, or are received with missing data required for calculating the result; this delays reporting. This standard is a measure of the laboratory’s performance.
Data collection and reporting
Data source: screening laboratory
Responsible for data quality and completeness: screening laboratory
Responsible for submission: screening laboratory
Reported by: screening laboratory
Published by: screening laboratory
Reporting period
Annually by 30 June
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018
FASP-S06: test: completion of laboratory request forms T21, T18, T13 screening
Description
The proportion of laboratory request forms, including complete data prior to screening analysis, submitted to the laboratory within the recommended timeframe of 10 weeks plus 0 days to 20 weeks plus 0 days gestation.
Rationale
A number of essential data fields must be provided on the request form to:
- ensure a screening test for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome provides an accurate individual result for the pregnant woman at the earliest opportunity
- reduce unnecessary delays in processing the test
See minimum data fields for a laboratory screening request form.
Definition
Numerator: number of submitted laboratory request forms with completed data for all the following fields at the initial request:
- sufficient information for the woman to be uniquely identified
- woman’s correct date of birth
- maternal weight
- family origin
- smoking status
- ultrasound dating assessment, CRL measured to one decimal point and head circumference (HC) in millimetres
Denominator: number of request forms for T21, T18, T13 screening submitted to the laboratory within the reporting period during the recommended timeframe for analysis of 10 weeks plus 0 days to 20 weeks plus 0 days gestation (inclusive). This includes request forms for T21 screening using combined or quadruple testing and T18 and T13 screening using combined testing.
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
Performance thresholds
Acceptable level: greater than or equal to 97.0%
Achievable level: 100.0%
Caveats
All services should aim to complete all fields on the laboratory request forms.
The acceptable threshold reflects the possibility that some women may not wish to supply their family origin or smoking status.
This standard measures initial laboratory requests, not subsequent or repeat requests.
Data collection and reporting
Data source: screening laboratory and ultrasound departments
Responsible for data quality and completeness: screening laboratory
Responsible for submission: screening laboratory
Reported by: maternity service
Published by: maternity service
This standard is also the key performance indicator FA1
Reporting period
Quarterly; data to be collated between 2 and 3 months after each quarter end
Deadlines: 30 September (Q1), 31 December (Q2), 31 March (Q3), 30 June (Q4)
Review dates
Date standard introduced: April 2010
Date standard last updated: April 2018
FASP-S07: referral: time to intervention T21/T18/T13 screening
Description
Timely communication of higher chance results.
Rationale
To provide assurance that individuals with higher chance results are referred in a timely manner and receive timely intervention where appropriate.
Definition
Numerator: number of women with a higher chance result offered an appointment within 3 working days
Denominator: number of higher chance results for first trimester combined screening and quadruple screening in the second trimester
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
FASP defines the national cut-off set at 1 in 150 at term for both first and second trimester screening tests. A woman with a result of 1 in 150 or greater (between 1 in 2 and 1 in 150), of having a pregnancy with T21, T18, T13 in the first trimester or T21 only in the second trimester will be considered to be in the ‘higher chance’ group and offered an invasive diagnostic test.
For women having screening using the combined test, dependent of their screening choice, up to 2 results are reported:
- a result for T21 and a result for T18 and T13
- a result for T21 only or T18 and T13 only
Performance thresholds
Acceptable level: greater than or equal to 97.0%
Achievable level: greater than or equal to 99.0%
Caveats
This standard counts the offer of an appointment within the specified timeframe. It does not count attendance at the appointment.
Offer is defined as direct contact with the woman - providers should be able to demonstrate that reasonable efforts were made to contact the woman. Where contact was not possible, this should be explained in the mitigations.
Data for each maternity service may be small and therefore would be aggregated and reported as regional or national figures.
Data collection and reporting
Data source: maternity service
Responsible for data quality and completeness: maternity service
Responsible for submission: maternity service
Reported by: maternity service
Published by: maternity service
Reporting period
Annually by 30 June
Review dates
Date standard introduced: April 2004
Date standard last updated: April 2018
FASP-S08: referral: time to intervention 18 weeks plus 0 days to 20 weeks plus 6 days of fetal anomaly ultrasound
Description
Timely referral (local and tertiary as clinically appropriate) when an anomaly is suspected or confirmed.
This standard is reported in 2 parts: S08a (local referrals) and S08b (tertiary referrals)
Rationale
To provide assurance that individuals with a suspected or confirmed anomaly are referred in a timely manner and receive timely intervention.
Definition
The cohort of women included in this standard is the total number of women in the reporting period who had a suspected or confirmed anomaly at the screening scan. Women are then categorised into either (a) or (b) dependent on the local referral pathway.
S08a - local referrals
Numerator: number of women referred locally and seen within 3 working days of the fetal anomaly scan
Denominator: women with a suspected or confirmed fetal anomaly referred locally
Standard S08a excludes women with a suspected or confirmed fetal anomaly where a referral is required to a tertiary fetal medicine centre for further investigation and care (as clinically appropriate as per local pathway).
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
S08b - tertiary referrals
Numerator: number of women referred to a tertiary centre and seen within 5 working days of the fetal anomaly scan
Denominator: women with a suspected or confirmed fetal anomaly referred to a tertiary centre
Standard S08b excludes women with a suspected or confirmed fetal anomaly where the referral is to an obstetric ultrasound specialist locally for ongoing investigation and care (as clinically appropriate as per local pathway). The numerator and denominator include those completing the fetal anomaly scan between 18 weeks plus 0 days to 23 weeks plus 0 days weeks of pregnancy.
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
Performance thresholds
Acceptable level: greater than or equal to 97.0%
Caveats
Where women are referred to a tertiary fetal medicine centre, good communication and feedback to the referring unit or clinician is necessary to enable local units to report on this standard.
Data collection and reporting
Data source: maternity service, ultrasound department, tertiary centre
Responsible for data quality and completeness: maternity service
Responsible for submission: maternity service
Reported by: maternity service
Published by: maternity service
Reporting period
Annually by 30 June
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018
FASP-S09: diagnosis or intervention: diagnostic tests fetal anomaly screening
Description
Test turnaround times - Quantitative Fluorescence-Polymerase Chain Reaction (QFPCR)
Test turnaround times - karyotype
This standard is reported in 4 parts: S09a (QFPCR T21, T18, T13), S09b (karyotype T21, T18, T13), S09c (QFPCR fetal anomaly ultrasound) and S09d (karyotype fetal anomaly ultrasound)
Rationale
To provide assurance of timely information to enable ongoing decisions or actions.
Definition
S09a QFPCR testing for higher chance T21, T18, T13
Numerator: number of QFPCR results reported within 3 calendar days of sample receipt
Denominator: number of samples received for QFPCR testing where the indication for genetic testing is a higher chance T21, T18, T13 screening result issued in the reporting period
T21, T18, T13 higher chance screening result is defined as a result from combined screening for T21 and or T18 and T13, or from quadruple testing for T21 using national cut off.
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
S09b Karyotype testing for higher chance T21, T18, T13
Numerator: number of karyotype results reported within 14 calendar days of sample receipt
Denominator: number of samples received for karyotype testing where the indication for genetic testing is a higher chance T21, T18, T13 screening result issued in the reporting period
T21, T18, T13 higher chance screening result is defined as a result from combined screening for T21 and or T18 and T13, or from quadruple testing for T21 using national cut off.
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
S09c QFPCR testing for fetal anomaly ultrasound
Numerator: number of QFPCR results reported within 3 calendar days of sample receipt
Denominator: number of samples received for QFPCR testing where the indication for genetic testing is a suspected or confirmed anomaly detected on the 18 weeks plus 0 days to 20 weeks plus 6 days fetal anomaly ultrasound undertaken in the reporting period
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
S09d Karyotype testing for fetal anomaly ultrasound
Numerator: number of karyotype results reported within 14 calendar days of sample receipt
Denominator: number of samples received for karyotype testing where the indication for genetic testing is a suspected or confirmed anomaly detected on the 18 weeks plus 0 days to 20 weeks plus 6 days fetal anomaly ultrasound undertaken in the reporting period
We calculate performance by dividing numerator by denominator and multiplying by 100 to give a percentage.
All denominators above exclude samples referred for genetic testing where the only indication for testing is an increased NT. FASP recommends all women who accept first trimester screening must have all components of the screening test completed - NT and biochemistry.
Performance thresholds
Acceptable level: 90.0% of rapid aneuploidy QFPCR results should be reported within 3 calendar days of sample receipt in the laboratory.
Acceptable level: 90.0% of karyotype results should be reported within 14 calendar days of sample receipt in the laboratory.
Caveats
Thresholds are set at 90.0% to allow for a number of samples where a result is not possible to give a diagnostic result due to slow growing cultures where, for example, insufficient sample was received by the laboratory for processing or sub-optimum samples (for example, maternal cell contamination).
All laboratories should aim to maintain adequate reporting times.
Data collection and reporting
Data source: diagnostic laboratories
Responsible for data quality and completeness: diagnostic laboratories
Responsible for submission: Association for Clinical Genetic Science (ACGS)
Reported by: diagnostic laboratories
Published by: diagnostic laboratories
Reporting period
Annually by 30 June
Review dates
Date standard introduced: April 2015
Date standard last updated: April 2018