Down’s syndrome screening quality assurance support service
This document explains the quality assurance support service for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome screening (DQASS).
Applies to England
Purpose
The main aim of DQASS is to monitor and support the quality and effectiveness of Down’s syndrome (T21), Edwards’ syndrome (T18) and Patau’s syndrome (T13) screening in England.
DQASS provides feedback and support to laboratories, sonographers, the Screening Quality Assurance Service (SQAS) and to the NHS fetal anomaly screening programme (NHS FASP). The analyses provided by DQASS are used to improve the performance of the screening programme through feedback on all aspects of the test to laboratories, ultrasound departments and commercial suppliers.
Software used by screening laboratories must adhere to the specification for the chance result(s) calculation.
How DQASS works
DQASS works on a rolling audit of screening test data on a 6-monthly cycle. The statistical analyses monitor various components of the screening process such as the overall standardised screen positive rate (SPR) and specific adjustments for ethnicity, smoking and other factors applied to individual biochemical markers. Through meta-analyses, DQASS provides information on effects of factors such as smoking that is used to improve screening performance.
The NHS FASP service specification requires all screening laboratories providing NHS screening to participate in DQASS. The service is provided to screening laboratories and individual ultrasound practitioners across England.
The screening support sonographer
The NHS FASP recommends the provider has a screening support sonographer (SSS) and a deputy SSS with administrative support. These roles oversee the implementation, delivery and monitoring of the ultrasound aspects of the service. The SSS and deputy must actively participate in the DQASS process including submission of a minimum of 25 paired measurements on a 6-monthly basis.
The SSS should:
- follow NHS FASP requirements as specified in the NHS FASP handbook and by DQASS
- attend provider and commissioner led antenatal and newborn (ANNB) screening programme boards to represent the ultrasound service, and take the DQASS laboratory and ultrasound summary reports to these meetings
- put in place an on-going education and training programme for ultrasound practitioners
- undertake departmental review of ultrasound images including a log of dates that the image review was performed (this is required as evidence for SQAS)
- keep an accurate and up-to-date database of ultrasound practitioners and associated identity codes and inform DQASS:
- and the screening laboratory when a new ultrasound practitioner starts, or existing practitioners leave the provider and if known, their new place of work
- if any of their ultrasound practitioners work at other sites
- of new trainees to generate a unique DQASS identity code
- of the accuracy of DQASS/Fetal Medicine Foundation (FMF) identity codes and of any changes before the 6-monthly data submission
- of any omissions or errors in the DQASS reports (detailed ultrasound report for each individual ultrasound practitioner or ultrasound department summary report for each ultrasound provider) so an updated report can be issued if appropriate
- if there are any changes to their service that could impact their DQASS reports, for example new ultrasound machines
- monitor throughput for each ultrasound practitioner and put in place a locally agreed action plan to enable them to meet the minimum throughput
- send and provide feedback on DQASS detailed ultrasound reports for each individual ultrasound practitioner
- implement and monitor any supportive red flag action plans; in cases where the ultrasound practitioner works at more than one site, the SSS should work together with the other site’s SSS and the ultrasound practitioner to develop the supportive action plan
- review the SSS resource every 2 years; all new SSS and deputy SSS should review the SSS resource when they start in the role
The SSS should also have a local documented process for the above actions.
DQASS identity codes
Ultrasound practitioners must have a unique identity code matched to the ultrasound department(s) where they work to participate in DQASS.
Trainee ultrasound practitioners
A trainee will need a unique DQASS identity code once they are able to achieve nuchal translucency (NT) and crown rump length (CRL) measurements with minimal guidance from the supervising practitioner.
A DQASS identity code is different from a FMF identity code.
The SSS should email DQASS at [email protected] with the practitioner’s name and their associated hospital/unit(s) to obtain a DQASS identity code for the trainee.
DQASS will issue an identity code with the suffix ‘T’ to indicate a practitioner in training (for example, 123456T).
The training process should take no longer than 6 months. The training code ‘T’ will remain valid for this time. If training is not completed within 6 months, the SSS should document the reasons and contact DQASS.
The trainees should follow the 2-part training process as outlined in education and training for ultrasound practitioners in the NHS FASP handbook.
New ultrasound practitioners from overseas
All new ultrasound practitioners from overseas require a unique identity code. The NHS FASP handbook provides guidance to follow before qualified ultrasound practitioners participate in combined screening.
Ultrasound practitioners who need an FMF identity code to access screening software
Ultrasound practitioners in some departments using specific screening software to calculate the combined screening result need an FMF identity code. In these cases, DQASS will use the practitioner’s FMF code to identify the practitioner and will not issue a separate DQASS identity code. The FMF identity code is issued by the FMF and is a separate process from DQASS.
The SSS should contact DQASS if they have an ultrasound practitioner with an FMF identity code from outside England. This is to make sure that the code is not duplicated with FMF identity codes already used in England.
Data needed for DQASS
Any new screening laboratories, or laboratories wishing to set up a new network, should contact DQASS to register an intention to supply data. Following registration, DQASS will issue a date for data submission.
Laboratories providing NHS screening submit data every 6 months based on the DQASS schedule. It is important that screening laboratories submit data on time (the first working day of the scheduled month) to enable timely reporting and feedback. DQASS should be contacted if data submission is anticipated to be late.
A designated person in each laboratory must provide the data specified for a 6-month period in spreadsheet format with anonymised individual patient data contained in separate rows. Data provided should only include screening performed as part of NHS FASP using either combined screening or quadruple screening strategies. Data related to other testing strategies or private screening arrangements, should be removed by the laboratory before the data is submitted to DQASS.
The laboratory should liaise with the SSS to make sure the ID codes for the ultrasound practitioners are up to date and that the codes can be matched to an ultrasound department, to enable feedback to be given.
Each column should correspond to a specific data field. The first row should contain the variable label. For the combined test, each row should correspond to a fetus. For the quadruple test each row should correspond to a pregnancy.
If some of the specified data fields are not recorded then a blank column, or a column with N/A in each cell, should be reported. Although it is not used for the statistical analyses, additional information for comparison purposes should include:
- current medians by day, or regression equation used, indicating both the gestational age and weight adjustment equations used
- current algorithm parameters, means, standard deviations, correlation coefficients for both the unaffected and affected (T21 and T18/T13) outcomes
- dates of lot and median changes and corresponding lot numbers
- calibration or quality-control changes
- analyser and software used
Any specific queries should also be attached.
Data screening laboratories need to provide to DQASS
Maternal pregnancy characteristics
Pseudo identifier
Maternal age at expected date of delivery
Last menstrual period date
Maternal weight at test date in kg to one decimal place
Smoking: stopped before pregnancy / stopped during pregnancy / smoker
Smoking number per day
Nicotine replacement (e-cigarettes / patches / other) if included on request form and available
Ethnicity
Diabetes: No / type 1 / type 2
Insulin: Yes / No
Previous trisomies: T21, T18, T13
Twin / singleton
Fetus number (1, 2)
Chorionicity: monochorionic (MC), dichorionic (DC)
Biochemical markers
Blood sample date
Gestational age in days at blood sample date
Alpha fetoprotein (AFP) concentration 1
uE3 concentration 1
Total human chorionic gonadatropin (hCG) concentration 1
Free Beta hCG concentration 1
PAPP-A concentration 1
Inhibin concentration 1
AFP multiple of the median (MoM) 2
uE3 MoM 2
Total hCG MoM 2
Free Beta hCG MoM 2
PAPP-A MoM 2
Inhibin MoM 2
1 In cases where biochemical measurements of a particular marker are produced from different instruments, the instrument used should be given in a separate field
2 MoM values should be provided after all corrections for gestation, weight, ethnicity, smoking, diabetics on insulin, twins, were applied.
Ultrasound scan
Scan date
CRL in mm to a minimum of one decimal place
Head circumference (HC) in mm to a minimum of one decimal place
NT in mm to a minimum of one decimal place
Identity code of ultrasound practitioner and ultrasound department
Measurements must not be rounded up or down.
Chance results
Prior chance for T21
Prior joint chance for T18/T13
Chance at term for T21
Joint chance at term for T18/T13
Submission dates for laboratories (start of month)
October and April
Birmingham Women’s NHS Foundation Trust
Mid Essex Hospitals NHS Trust (Broomfield Hospital)
Nottingham University Hospitals NHS Trust
Bolton NHS Foundation Trust
Bolton/Nottingham (BoNo) second trimester network
November and May
Oxford University Hospitals NHS Foundation Trust
Kettering General Hospital NHS Foundation Trust
Barking, Havering and Redbridge University Hospitals NHS Trust (King George Hospital)
Birmingham/King George/Kettering (BKK) second trimester network
January and July
King’s College Hospital NHS Foundation Trust
Sheffield Teaching Hospitals NHS Foundation Trust (Northern General Hospital)
University College London Hospitals NHS Foundation Trust / Medway Maritime Hospital first trimester network
Cambridge/Norfolk and Norwich University Hospitals NHS Foundation Trust (CaNN) first trimester network
February and August
Portsmouth Hospitals NHS Trust (Queen Alexandra Hospital)
Royal Devon and Exeter NHS Foundation Trust
March and September
Newcastle Hospitals NHS Foundation Trust
North Bristol NHS Trust (Southmead Hospital)
The Leeds Teaching Hospitals NHS Trust
University Hospitals Coventry and Warwickshire NHS Trust
Cambridge/Oxford/Leeds/Newcastle (COLN) second trimester network
Report types
DQASS undertakes a range of statistical analyses on the data provided and produces reports summarising activity and performance.
Four reports are produced for each 6-monthly data submission. These consist of a:
- detailed laboratory report for each screening laboratory/network
- summary laboratory/network report
- feedback plot (NT/CRL) for each individual ultrasound practitioner
- feedback plot (NT/CRL) summary report for each ultrasound provider
In addition, 2 national cycle reports are produced at the end of each 6-month cycle. These are the:
- laboratory/network cycle report
- ultrasound cycle report
More information about these reports is available in the 6 DQASS report types guidance.
DQASS report recipients
The 6 reports produced by DQASS are made available to numerous stakeholders including laboratory leads, individual sonographers via SSSs, NHS FASP, SQAS and public health commissioning teams via SQAS. Recipients for each of the reports are as follows:
Detailed laboratory/network report recipients
Laboratory lead
Summary laboratory/network report recipients
Laboratory lead
SSS and deputy
NHS FASP
SQAS
Public health commissioning teams via SQAS
Individual feedback plot (NT/CRL) report recipients
Individual ultrasound practitioners via SSS
SQAS (only red flagged data)
Feedback plot (NT/CRL) summary report recipients
SSS and deputy
SQAS
Public health commissioning teams via SQAS
Laboratory/network cycle report recipients
Laboratory lead
NHS FASP
SQAS
Ultrasound cycle report recipients
SSS and deputy
NHS FASP
SQAS
Contact DQASS
Down's syndrome screening Quality Assurance Support Service (DQASS)
DQASS
Room N15
Plymouth Science Park
1 Davy Road
Derriford
Plymouth
Devon
PL6 8BX
Email [email protected]
Telephone 01752 764 437
Resources
Guidance
The NHS FASP handbook provides practical guidance to support healthcare professionals and stakeholders in providing the NHS FASP screening pathways.
e-Learning modules
e-Learning modules can be accessed on e-Learning for Healthcare. Relevant modules are:
- screening for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome
- first trimester resource for ultrasound practitioners
- fetal cardiac e-Learning
- 20-week screening scan resource for ultrasound practitioners
- SSS resource
Nuchal translucency and crown rump length diagnostic plot self-assessment tool
A diagnostic plot self-assessment tool is provided to assist monitoring of NT and CRL measurements. We recommend using it weekly or monthly depending on the number of scans performed. The tool should not be used at the time of the scan to compare measurements to the FMF reference curve.
Software specification
The chance calculation software specification provides details to be incorporated into the software package to achieve consistent chance results across England. Some variables entered into the software are defined by the local user because of the reagents used for screening and the characteristics of the screened population. These would normally be decided by the laboratory in collaboration with DQASS.
DQASS reporting website
The DQASS reporting website is a secure online portal for the SSS and deputy to access the DQASS reports (Individual feedback plot (NT/CRL) report and Feedback plot (NT/CRL) summary report) for the ultrasound practitioners in their department. It also contains several useful resources for the SSS, deputy SSS and ultrasound practitioners.
This publication was previously published by Public Health England, which closed on 30 September 2021.
Updates to this page
Published 1 January 2014Last updated 8 October 2024 + show all updates
-
Added clarification that publication was previously published by Public Health England.
-
Updated process for red flag to include practitioner working at more than one site. Updated laboratory submission information. Added clarification to throughput description and information on DQASS reporting website. Removed reference to national and regional QA and PHE.
-
Updated process for red flag to include practitioner working at more than one site. Updated laboratory submission information. Added clarification to throughput description and information on DQASS reporting website. Removed reference to national and regional QA and PHE.
-
Updated process for red flag to include practitioner working at more than one site. Updated laboratory submission information. Added clarification to throughput description and information on DQASS reporting website. Removed reference to national and regional QA and PHE.
-
Added 'Nuchal translucency and crown rump length diagnostic plot self-assessment tool' information to 'Resources' section.
-
Updated with new information on the screening support sonographer and report types, in addition to submission dates for laboratories to reflect new screening laboratory networks.
-
Updated list of laboratories under submission date, laboratory network names and other minor DQASS changes.
-
Added link to laboratory cycle report.
-
Updated DQASS detailed guide.
-
First published.