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Detection rates of a national fetal anomaly screening programme: A national cohort study
Nicholas Aldridge1, Pranav Pandya2, Judith Rankin3
1National Congenital Anomaly and Rare Disease Registration Service, NHS Digital, Leeds, UK.
Insights
The fetal anomaly (FA) scan effectively detects most physical conditions screened by the NHS Fetal Anomaly Screening Programme. Detection rates for many conditions exceed 2010 expectations, improving prenatal diagnosis.
Area of Science:
- Medical Imaging
- Prenatal Diagnosis
- Public Health Screening
Background:
- The National Health Service (NHS) Fetal Anomaly Screening Programme (FASP) utilizes fetal anomaly (FA) ultrasound scans to detect physical conditions.
- Assessing the real-world performance of FA scans is crucial for evaluating and improving prenatal screening effectiveness.
Purpose of the Study:
- To quantify the condition-specific detection rates for 14 physical conditions assessed by the NHS FASP FA ultrasound scan.
- To compare the observed detection rates against established benchmarks.
Main Methods:
- A retrospective audit was conducted on 12,694 diagnoses across a 3-year national cohort (April 2017–March 2020).
- Data included pregnancies booked for maternity services in English NHS and crown-dependency hospital trusts.
- Active multi-source ascertainment, linkage, audit, and validation of clinical information were employed to determine positivity thresholds for FA scan detection.
Main Results:
- Detection rates varied by condition, with high rates for anencephaly (96.3%), bilateral renal agenesis (98.7%), and spina bifida (93.8%).
- Moderate detection rates were observed for conditions like atrioventricular septal defect (69.2%) and congenital diaphragmatic hernia (60.8%).
- Overall, FA scan performance generally met or exceeded expectations set in 2010 for most screened conditions.
Conclusions:
- The FA scan demonstrates strong performance, exceeding 2010 expectations for the majority of screened physical conditions.
- For conditions with lower detection rates, many affected fetuses/babies are identified through other means prior to the FA scan.
- The findings support the continued role of FA scans within the NHS FASP for prenatal screening.
Objective:
To measure condition-specific detection rates for 14 physical conditions screened for by the NHS fetal anomaly screening programme (FASP) fetal anomaly (FA) ultrasound scan.
Design:
Retrospective audit of 12 694 diagnoses across a 3-year national cohort.
Setting:
All English NHS and crown-dependency hospital trusts providing maternity services.
Population:
Pregnancies booked for maternity services with an expected date of delivery between 1 April 2017 and 31 March 2020 and at least one diagnosis of a condition screened for by FASP.
Methods:
Active multi-source ascertainment, linkage, audit and validation of clinical information to identify the subset of diagnoses meeting the condition-specific positivity threshold for the FA scan.
Main Outcome Measure:
The accuracy of the FA scan compared with diagnostic reference standards.
Results:
FA scan detection rates were: anencephaly 96.3% (95% confidence interval [CI] 81.7-99.3%), atrioventricular septal defect: 69.2% (95% CI 65.8-72.4%), bilateral renal agenesis: 98.7% (95% CI 95.4-99.6%), cleft lip: 89.5% (95% CI 87.8-90.9%), congenital diaphragmatic hernia: 60.8% (95% CI 56.5-65%), Edwards syndrome: 73.8% (95% CI 67.5-79.3%), exomphalos: 59.4% (95% CI 49.4-68.7%), gastroschisis: 88.6% (95% CI 79-94.1%), hypoplastic left heart syndrome: 92.7% (95% CI 90-94.8%), lethal skeletal dysplasia: 93.2% (95% CI 88.6-96%), Patau syndrome: 82.3% (95% CI 72.4-89.1%), spina bifida: 93.8% (95% CI 91.8-95.3%), tetralogy of Fallot: 75.4% (95% CI 72.1-78.4%) and transposition of the great arteries: 84.9% (95% CI 81.7-87.5%).
Conclusions:
The performance of the FA scan is above the expectations set in 2010 for most conditions. For the remaining conditions, the majority of fetuses and babies affected are detected before the FA scan.
