Review Fetal anomaly ultrasound scanning: the development of a national programme for England

Transcription

1 /toag Fetal anomaly ultrasound scanning: the development of a national programme for England Authors Pat Ward / Peter Soothill Key content: Extensive work has been undertaken since 2005 by the NHS Fetal Anomaly Screening Programme and the UK National Screening Committee to implement a national ultrasound screening programme for fetal anomalies in England. Fetal anatomy is assessed between 18 and 21 weeks of gestation. Learning objectives: Clinicians will be able to compare their practice with the national requirements. To be made aware of the most up-to-date guidance on the assessment of fetal anatomy during the ultrasound scan and the minimum number of conditions that would be expected to be detected. Ethical issues: What ethical complexities are there with regard to screening a potential person (the fetus) through another (the mother)? What is the value of screening using a diagnostic tool such as ultrasound? Keywords British Medical Ultrasound Society / National Institute for Health and Clinical Excellence / normal variants / trisomy 21 / UK National Screening Committee Please cite this article as: Ward P, Soothill P. Fetal anomaly ultrasound scanning: the development of a national programme for England. The Obstetrician & Gynaecologist. Author details Pat Ward RM RGN CHSM MA National Programme Director NHS Fetal Anomaly Screening Programme, University of Exeter, Devon, EX4 4RN, UK Peter Soothill Emeritus Professor of Fetal Medicine and Consultant St Michael s Hospital, Southwell Street, Bristol BS2 8EG UK; and Chairman of the NHS FASP Steering Committee NHS Fetal Anomaly Screening Programme, University of Exeter, Devon, EX4 4RN, UK peter.soothill@bristol.ac.uk (orresponding author) 211

2 The Obstetrician & Gynaecologist Introduction Ultrasound has been used to look at the fetus in the uterus for more than 30 years in the UK and it is now an accepted technique used worldwide to assist the clinical management of pregnancy. Some argue that its use has become so extensive that it is replacing the traditional practical skills of obstetrics and midwifery. Although its use and development has become acceptable practice in the National Health Service (NHS), it is only recently that sonographic investigations have begun to be formally accepted as part of a national screening programme. Indeed, scanning for fetal anomalies in pregnancy sits quite pertinently as a screening tool rather than as a purely diagnostic or clinical management tool. Like most important innovations, scanning in pregnancy was introduced initially on an individual basis in the highest risk cases. This was done primarily by enthusiasts for the potential of the technology, rather than following evidence of effectiveness, which in the early stages was absent because of its being a new concept. Today we would not introduce something without sufficient evidence to ensure its safety and effectiveness or without undertaking an economic evaluation. In many respects, therefore, one of the most difficult problems to resolve in changing this practice has been to redesign an established but chaotic system into one that adheres to the principles of a national screening programme. History In 1957 Tom Brown and Ian Donald invented and constructed the prototype of the first compound B-mode contact scanner. The technology progressed but it was not until 1965 that the first real-time scanner was developed by Walter Krause and Richard Soldner. One of its first uses, in 1966, was to assist in performing amniocentesis to look for trisomy 21 in older women. 1 Screening by age, followed by diagnostic amniocentesis, allowed a basic risk assessment and diagnosis to be available for trisomy 21 for the first time. Although those initial ultrasound images were quite unclear by today s standards, the technology developed and grew, becoming more widespread in the 1970s and 1980s. In 1969 the NHS founded the British Medical Ultrasound Group, which was formed by members of the Hospital Physicists Association and the British Institute of Radiology. The group changed its name in 1977 to the British Medical Ultrasound Society and it is still in existence today. The main use of ultrasound in obstetrics was to replace X-ray techniques (which were mostly used to assess presentation and growth), which had radiation risks to the unborn baby. The early 1990s saw further improvements in image quality and an even clearer picture of the fetus inside the uterus could be obtained. Still relatively few studies had reported on the rationale for continuing to implement this as a clinical service, however, and even fewer identified the process as a screening test: more often there was an emphasis on diagnostics. 2,3 Moves to develop fetal anomaly screening into a national screening programme Following a national survey of NHS services in 2002 by the NHS Fetal Anomaly Screening Programme (NHS FASP), the UK National Screening Committee (UKNSC) identified that the midtrimester scan was being used as a screening test by the majority of maternity units in England. 4 The national survey showed that 97% (195/202) of units offered a second-trimester fetal anomaly scan to all women, with the seven offering one on a selective clinical basis. At that time, therefore, ultrasound in pregnancy for fetal anomalies was well established in clinical practice as a population screening programme even if this was not the declared intention of clinicians or pregnant women. In 2003 further guidance 5 was developed by the National Collaborating Centre for Women s and Children s Health and published by the National Institute of Clinical Excellence (now the National Institute for Health and Clinical Excellence [NICE]), which supported the requirement for all pregnant women to be offered an ultrasound scan aimed at detecting abnormalities in the fetus. Following recommendations from NICE, the UKNSC supported the decision that this procedure should be part of a national screening programme, with all pregnant women being offered an ultrasound scan to screen for fetal anomaly. The UKNSC is responsible for providing recommendations to UK ministers on the implementation or cessation of screening programmes. That remit encompasses developing policy, setting standards and producing training materials and information for patients, all underpinned with quality assurance systems to measure the services against standards to improve the quality of care. Previously, these processes were applied to the NHS breast and cervical cancer screening programmes and, more recently, to screening for trisomy 21, 6 newborn hearing, diabetic retinopathy and infectious diseases during pregnancy. In January 2009 a government commitment to provide and fund these programmes was set out in the NHS Constitution. 7 Links to other screening programmes The work of the ultrasound programme is very closely associated with screening for trisomy 21, which is managed from the same national (NHS FASP) programme centre. Implementing 212

3 dating scanning so that the risk for trisomy 21 can be accurately assessed has been a key focus of development in England and is now fully in place. To some degree the early dating scan is progressing towards being an early anomaly scan that can detect major structural anomalies such as anencephaly and which can screen early for trisomy 18 and 13. Although early screening is usually aimed at aiding early decision making by parents, screening for conditions such as haemoglobinopathies and infectious diseases is also done at this stage. It would be most beneficial to women if all the testing could be undertaken at one appointment. Ultrasound is, by nature, a non-selective process of examining the fetus and, therefore, neither pregnant women nor sonographers prospectively have a clear idea about what will be identified or its significance. In 2000 the Royal College of Obstetricians and Gynaecologists (RCOG) attempted to define the purpose of the scan examination; the structure of the routine ultrasound exam was also described. 8 Although this provided guidance for the service to work to, little was known about the extent to which it was implemented in the NHS or its effectiveness as a screening tool, or even whether it was aligned with the screening principles of Wilson and Jungner 1968 as agreed by the World Health Organization. 9 The criteria set out by Wilson and Jungner referred to screening as a public health initiative and the basic concepts of fetal screening were not described. In the original RCOG publication 8 there is no reference to the principles of fetal screening or the criteria that should be used to screen through a second person, the mother. One of the basic principles of population screening programmes is that they must produce more good than harm. There is also a central principle of utility and beneficence: the maximum benefit for the majority set against minimising harm. In the ultrasound anomaly screening programme the potential harm is perceived to be the heightened anxiety of a false positive result or distress at a false negative one and the possibility of the loss of a normal fetus following invasive investigation based on false positive information. It may be said that screening a fetus through a second person, i.e. the mother, carries an even greater imperative to ensure that standards are high and that more good and less harm are produced. With this in mind, it is crucial that there is a centralised process for setting standards and that there are mechanisms in place for measuring and improving standards. Two of the main principles our culture supports are the avoidance of false positive information (as shown, for example, by the recent approaches to normal variants or soft markers) and autonomy of choice. Normal variants were used formerly either to provide an initial risk assessment or to recalculate a trisomy 21screening risk in a pregnancy but not necessarily using appropriate statistical methods. The rights of the individual have changed in some respects since the foundation of the NHS, when care was paternalistic and direct decisions were made for patients by doctors: patients are now provided with all the information they need to enable them to make a fully informed choice pertinent to their lifestyle. This is always taken to mean within the constraints of available services within the NHS. There has to be a balance in the NHS between ensuring that money is spent effectively to obtain the best patient outcome and, equally, so that the majority can benefit. Quality-adjusted life years are another core consideration in public health management when implementing clinical services such as population screening. The provision of antenatal screening is not always a leading priority when competing for NHS resources. There are very distinct ethical views about screening and termination of the fetus with an abnormality; occasionally there is high level public debate about the rights of the fetus (in law the fetus does not have any) and the right to life in any circumstance. 10 Screening for fetal abnormalities carries with it many considerations and aspects, not least the ethical and lawful imperative and, clearly, some may find it difficult to separate the rights and needs of two individuals: the mother and the potential person, the fetus. However, the importance of offering screening to women who would never choose termination is also vital so that they have the chance to benefit from other options such as fetal therapy (for example, pleural amnniotic shunting for chylothorax or transfusion for anaemia causes of ascites), preparation for postnatal management (for example, changing the place of delivery for cardiac and surgically correctable abnormalities) and, simply, psychological preparation in the event that there are no therapeutic options. Timing of the to scan The timing of the anomaly scan has changed and evolved. In the 1970s 1980s, 16 weeks was often chosen, partly to link the scan for dating to alpha fetoprotein biochemical screening for neural tube defects. Subsequently most units chose 20 weeks because the position and orientation of the fetus is so often much better, especially for views of some structures such as the fetal heart. Some units then suggested waiting until 23 weeks for the anomaly scan because that might give the best sensitivity and specificity rates and would allow obstetric issues to be assessed at the same time; for example, using the uterine artery Doppler to predict placental dysfunction or cervical length for preterm labour risk. This issue was considered in detail and we now recommend that the fetal 213

4 The Obstetrician & Gynaecologist Box 1 Core aims and objectives of the to scan Identification of lethal abnormalities To be able to offer a choice about whether or not to continue with a pregnancy in which the baby is abnormal Identification of abnormalities for which there may be intrauterine treatments To be able to plan appropriate management of the pregnancy and delivery Identification of abnormalities amenable to immediate neonatal treatment To enable the development of care pathways for individual women. For serious abnormalities there are four possible pathways: Incompatibility with prolonged life Association with serious morbidity Amenability to postnatal treatment with relatively low morbidity Antenatal treatment anomaly scan be undertaken at to weeks. This allows sufficient time for reassessment and investigation of suspected problems, counselling and then decision making, before 24 weeks of pregnancy, after which, clause D of the laws governing termination of pregnancy needs to be carefully considered. 11 The purpose of the to scan From the perspective of the pregnant woman, ultrasound scanning is primarily a process for viewing the normality of the unborn baby rather than a test to screen for structural anomalies. From the clinical perspective it is seen as a useful tool to identify some structural abnormalities and provide confidence to support clinical management. This difference of perspective appears to have led to some confusion over what should be uniform good practice and what the limitations and benefits are of such technology. To take this forward and develop the service into a national screening programme a number of work streams were developed; however, there was a particular need to identify what the screening test should consist of and its purpose. The purpose of the ultrasound examination at to weeks of pregnancy was defined as being to identify pregnancies in which the fetus may be abnormal in order to allow investigation and so prepare the woman and her partner and allow changes in pregnancy management. The core aims and objectives are shown in Box 1. The potential value of screening for a condition was related to the above treatment options. During the review process of setting out conditions that constituted the screening test it was considered that as many as 33 conditions could be looked for by an ultrasound anomaly scan; however, the value of screening for them in the context of a screening programme required clarification. Obtaining accurate results via training and accreditation Achieving an accurate result from a screening test relies mostly on two people: the pregnant woman and the ultrasound operator. The pregnant woman needs to present at the right time, having understood what the test is about, and provide all the correct background history and information. The ultrasound operator needs to be able to use the machine effectively to acquire good images, interpret that image correctly and then provide a result. The very essence, though, of providing that result depends on the availability of appropriate technology, which is the scanning machine and scan recording and reporting software, and the interpretation of the imaging result by an appropriately trained individual. Even obtaining an image depends very much on the skill of the operator and not just the technology. In some respects, therefore, this is a very subjective screening test and not based on the mechanical, computerised interpretation of an accurate measurement as sometimes happens with laboratory tests. In a subjective assessment, moving real-time images provide more information than stills. Audit and evaluation of that process should form a key part of all screening ultrasound departments to ensure that services continue to improve. To help achieve the above, the NHS FASP have commissioned training packages. In England it is expected that all professionals who undertake an ultrasound scan for screening purposes will have a minimum recognised qualification of a postgraduate certificate and have received training from a higher educational institution. These can be sourced from the NHS FASP website (see Websites). Implementation One of the key objectives of the national programme was to develop a plan for both implementing a national screening service and developing structures to monitor and bring about further improvements. To achieve this, particular development stages along a 5-year process needed to be planned at an early point. The stages are shown in Figure 1. As ultrasound is so widely used in the NHS maternity service it was important to set a baseline for the efficacy of the test. It is well known that pregnant women value it as an opportunity to view their baby at an early stage and uptake rates of >95% are normal. Although it is used as a screening tool, it is quite difficult to establish the sensitivity and specificity rates of many conditions because of the paucity of literature and because prevalence changes with gestational age due to 214

5 Figure 1 Steps in developing a uniform national screening programme miscarriage/preterm labour. Attempts to identify rates have been made through the use of congenital anomaly registers such as the British Isles Network of Congenital Anomaly Registers (BINOCAR), but these only cover 50% of the UK and notification to these registers is by no means mandatory or complete. To produce detection rates of scanning for different conditions, evidence was taken from a variety of sources, including the NICE guideline. 5 The NHS FASP commissioned a review of the literature reviewing the evidence of detection rates into synoptic tables for comparison. 12 The available literature, however, is limited, particularly in relation to the more uncommon conditions. The principle was developed and agreed that to screen for a condition, the minimum number needed to be detected by screening should be no lower than 50%. The conditions that are screened for as a minimum from 2010 in the NHS for England, despite the general paucity of evidence, are listed in Table 1 and the expected detection rates were included based on available evidence. Setting standards Setting standards for the service to work towards provides clear information for the pregnant woman as to what to expect and guides working practices for the professional. The main core of standards and pathways that underpin this have been published by the NHS FASP 13 and these will take us forward into the next decade.the working standards envelop all aspects of the service, including information giving, the consent process, image capture and storage, machine specification and documentation. We have developed agreement about which structures should be examined to constitute a minimum scan: this checklist is shown in Box 2. All women are expected to be offered an examination of those structures at the to scan. If these structures cannot be imaged sufficiently to report the structure as appearing normal, referral to a diagnostic unit is stipulated. National occupational standards have also been developed by Skills for Health 14 to complement the main working standard. Together, therefore, there is now a complete set of guidance for all professionals, including new information from the British Medical Ultrasound Society on which measurements should be used for dating a pregnancy. 15 Condition Detection rate (%) Anencephaly 98 Open spina bifida 90 Cleft lip 75 Diaphragmatic hernia 60 Gastroschisis 98 Exomphalos 80 Serious cardiac abnormalities 50 Bilateral renal agenesis 84 Lethal skeletal dysplasia 60 Trisomy 18 (Edwards syndrome) 95 Trisomy 13 (Patau syndrome) 95 Ultrasound normal variants (soft markers) There is no significant evidence of any direct physical risk from the ultrasound used in scanning. There are, however, major risks from scanning resulting from misinformation, anxiety or false positive results. An example of this type of risk is from the use of screening for soft markers, or normal variants as they are now called, such as choroid plexus cysts, two-vessel cords and echogenic foci in the heart. Indeed, the possible value of identifying normal variants as a tool for identifying conditions such as trisomy 21 has greatly decreased as the national screening programme for trisomy 21 has developed and been introduced systematically. The NHS FASP has worked extensively since 2008 to address this issue and has developed a final agreement on the way forward for the use of normal variants in clinical practice. A statement was issued in January 2010 setting out that soft markers (normal variants) should not be used to assess the risk for a chromosomal condition or as a screening tool. 16 It is likely this will greatly reduce the anxiety engendered by ultrasound screening, while the detection rate in women who wish to be informed about trisomy 21 will continue to increase; for example, because of combined testing, with an approximately 75% detection rate for a 3% positive rate. Audit and governance A principle of any screening programme is that there should be information on its effectiveness using sensitivity and specificity as the main audit criteria. Although it was clear that ultrasound was engrained in NHS maternity care, the 2002 ultrasound survey 4 identified a lack of auditing of this test. Eighty percent of maternity units were unable to provide detection rates for certain basic Table 1 Conditions screened for as a minimum in the NHS in England 215

6 The Obstetrician & Gynaecologist Box 2 Checklist of minimum number of structures to be examined by ultrasound scan for all women at the to scan 13 Number Area Structure View 1 Head and neck Skull Shape Neck Subjective: measure nuchal fold if it looks Skin fold (nuchal fold) increased Brain Cavum septum pellucidum Ventricular atrium Cerebellum 2 Face Lips Coronal view 3 Chest Heart Refer to Fetal Cardiac Protocol Four-chamber view Outflow tracts Lungs 4 Abdomen Stomach Transverse, sagittal Stomach and short intrahepatic section of umbilical vein Abdominal wall Transverse Bowel Renal pelvis Transverse: measure antero-posterior view if looks increased Bladder Sagittal and transverse 5 Spine Vertebrae Sagittal and transverse Skin covering Sagittal and transverse 6 Limbs (a) Femur Length (one leg only) Limbs (b) Hands Metacarpals (right and left) Visible (not counted) Feet Metatarsals (right and left) Visible (not counted) 7 Uterine cavity Amniotic fluid Subjective volume Placenta Visible and position noted abnormalities such as anencephaly, with only 28% monitoring false positive rates. Clearly, as we move the organisation of this service into a national screening programme, mechanisms for assessing and delivering the effectiveness of the screening test will be required. Having set standards, the NHS FASP has already set out an audit specification for use by service providers. This will require those responsible for IT systems to develop systems to support this function. For example, NHS Connecting for Health is working to establish a computerised integrated patient record system for England. There are other commercial systems that could be integrated into NHS services, which could assist in the audit cycle. Once all units have such systems, it will be possible to collate national statistics centrally and provide the final part of the screening implementation, audit and improvement cycle. This principle has been demonstrated very successfully by the use of information technology to register practitioners and to audit and improve performance nationally with nuchal translucency measurements in trisomy 21screening by the Fetal Medicine Foundation. Bodies such as NHS Connecting for Health and computerised radiology information systems have been entrusted with putting in place a national as well as local audit system. One thing that will be difficult to correlate fully is outcome data for all screened pregnancies. Joining antenatal fetal data that is part of the mother s record to the newborn baby s record has still to be developed and organised; however, it may be possible to do this using the birth notification, which is the one document in which information about the baby, the mother and any physical abnormalities is collated in one place. Summary There has been an extensive amount of work undertaken over the last 5 years by the NHS FASP and the UK NSC to lead and set out the direction of ultrasound screening in maternity services in this country. This includes changes to the way services are run, reconfiguration of referral pathways and identification of where resources can be used more effectively to achieve the standards set. What is clear is that we now have the basis for a national screening programme for fetal anomaly ultrasound and not an archipelago of units offering and performing different things. Websites NHS Fetal Anomaly Screening Programme [ References 1 Steel MW, Breg WR Jr. Chromosome analysis of human amniotic-fluid cells. Lancet 1966;1: doi: /s (66) Ritchie K, Boynton J, Bradbury I, Foster L, Iqbal K, Kohli H, et al. Routine Ultrasound Scanning Before 24Weeks of Pregnancy. Health Technology Assessment Report 5. Glasgow: NHS Quality Improvement Scotland; Bricker L, Garcia J, Henderson J, Mugford M, Neilson J, Roberts T, et al. Ultrasound screening in pregnancy: a systematic review of the clinical effectiveness, cost-effectiveness and women s views. Health Technol Assess 2000;4:i vi, UKNational Screening Committee. Antenatal Ultrasound Screening Ultrasound Survey of England: UKNational Screening Committee National Programmes Directorate: Oxford; 2005 [ ultrasound/screening/nsc%20ultrasound_survey.pdf]. 5 National Institute for Health and Clinical Excellence. Antenatal Care: Routine Care forthe Healthy Pregnant Woman. Clinical Guidelines CG6. London: NICE; NHS Fetal Anomaly Screening Programme. Screening fordown s Syndrome: UKNSC Policy recommendations : Model of Best Practice. London: Department of Health;

7 7 National Health Service.The Handbook to the NHS Constitution for England. London: Central Office of Information; Royal College of Obstetricians and Gynaecologists. Ultrasound Screening. Supplement to Ultrasound Screening forfetal Abnormalities [ 9 Wilson JMG, Jungner G. Principles and Practice of Screening for Disease. Public Health Papers No. 34. Geneva: World Health Organization; 1968 [whqlibdoc.who.int/php/who_php_34.pdf]. 10 Jepson v The Chief Constable ofwest Mercia [2003] EWHC Abortion Act Bryant L, Fisher A, Vicente F. Fetal Anomaly Ultrasound Screening Programme Study: Literature Survey. Plymouth: Social Research & Regeneration Unit; 2007 [ und%20screening%20programme%20study%20.pdf]. 13 Donna Kirwan and NHS Fetal Anomaly Screening Programme in collaboration with the Royal College of Obstetricians and Gynaecologists, British Maternal and Fetal Medicine Society and the Society and College of Radiographers to Weeks Fetal Anomaly Scan National Standards and Guidance forengland. Exeter: NHS Fetal Anomaly Screening Programme; NHS Fetal Anomaly Screening Programme. National Occupational Standards and National Workforce Competences. As Developed by Skills forhealth, the SectorSkills Council forhealth and Collated by the NHS Fetal Anomaly Screening Programme. Exeter: NHS FASP; Loughna, P, Chitty L, Evans T, Chudleigh T. Fetal size and dating: charts recommended for clinical obstetric practice. Ultrasound 2009;17: doi: / x NHS Fetal Anomaly Screening Programme. Normal Variant Screening in Pregnancy. Programme Statement. Exeter: NHS FASP;