High throughput non-invasive prenatal testing (NIPT) for fetal RHD genotype testing was introduced as a county wide project by Taunton and Somerset NHS Foundation trust and Yeovil District Hospital. The technology was introduced as an option for pregnant women who are rhesus D-negative. The postpartum pathway has remained unchanged following implementation of this technology. This technology affects women in the antenatal period.
Offering NIPT for all pregnant women who are Rhesus D negative is in line with NICE DG25 recommendation (1.1) and will help reduce unnecessary use of the blood product anti-D immunoglobulin. This case study has been adapted from the Adoption support for high-throughput non-invasive prenatal testing for fetal RHD genotype: insights from the NHS and reflects the service at the time of resource publication (February 2017).
Aims & Objectives
- To target routine antenatal anti-D prophylaxis for women who are Rhesus-D negative (RHD), instead of treatment with anti-D for all pregnant women who are RHD negative.
- prevent unnecessary administration of blood products (anti-D immunoglobulin) and their associated risk
- avoid unnecessary painful injections for women where the NIPT for fetal RHD genotype is negative
- reduce the number of antenatal anti-D prophylactic clinic appointments needed, and the amount of anti-D immunoglobulin used
- increase availability of anti-D immunoglobulin for use following potential sensitising events (PSEs) in pregnancy where the NIPT result for fetal RHD genotype is positive
- reduce the anxiety associated with potential sensitising events for D-negative women where the NIPT result for fetal RHD genotype is negative
- provide information to allow D-negative women to make an informed decision about whether to have treatment with anti-D immunoglobulin.
Yeovil District Hospital NHS Foundation Trust provides care to approximately 185,000 people in south Somerset, North and West Dorset and parts of Mendip. There are 1500 babies born annually in Yeovil Hospital and they have approximately 80 midwives who work in an integrated team.
The antenatal team implemented high throughput non-invasive prenatal testing for fetal RHD genotype in June 2016. In their organisation the test is referred to as ffDNA, (free fetal DNA). The laboratory manager involved in the implementation is employed by Integrated Pathology Partnerships (iPP) which is part of a joint venture (Southwest Pathology Services LPP) with Taunton and Somerset and Yeovil District Hospital NHS Foundation Trusts and Integrated Pathology Partnerships. Pathology Services to both NHS Foundation Trust joint venture partners are provided by iPP. The ffDNA test is sent to NHS Blood and Transplant (NHSBT) for processing.
Prior to implementation of this project, all women who were Rhesus D negative were treated with Routine antenatal anti-D prophylaxis (RAADP) as per NICE guidance on routine antenatal anti-D prophylaxis for women who are rhesus D negative which recommends that all pregnant women who are D-negative are offered prophylactic anti-D immunoglobulin in the third trimester. In Yeovil this routinely happened as a single dose at the 28 week appointment. The new test is now used to determine the fetal RHD genotype which then directs prophylactic treatment with Anti D immunoglobulin. This is in line with NICE diagnostic guidance High-throughput non-invasive prenatal testing for fetal RHD genotype (DG25). If the fetal RHD is negative the woman does not need prophylactic treatment with anti D, if it is positive then she will have the anti D injection at 28 weeks.
The laboratory manager from Southwest Pathology Services and Consultant Haematologist from Taunton and Somerset NHS Foundation Trust presented a business case and clinical background to senior managers at Yeovil and Taunton.
The antenatal and new born screening coordinator is responsible for leading the implementation project with support from the laboratory manager at SPS in developing a local guideline. The guideline includes information on when to test, what to do with the sample, what to do with a positive and negative result and also what action to take in the event a false positive or false negative result is highlighted.
The screening coordinator provides training to all the midwives when they attend for their annual midwifery training update. They provided information packs for all midwives which included
- A letter to the midwives explaining about the project
- User guide
- Research paper
Women are informed of the test when they have their booking bloods done with community based midwives at 8-10 weeks. An assistant practitioner (AP) from the Yeovil maternity team does the ffDNA test at the first trimester 12 week screening appointment at the hospital. If blood results are not known (if the woman has booked late) or if there is uncertainty regarding the gestation (the test is not valid if used before 11+2 weeks) the team will inform the community midwives who will do the test at the 16 week appointment.
The results are returned to the laboratory via the specialist services electronic reporting system (Sp-ICE) used by NHSBT and manually transferred to the local laboratory system as ‘Pos, Neg, or inconclusive’, and double checked by a second laboratory operator. In order to reduce the risk of human error associated with manual data entry a logic rule was written to auto-populate remaining information once ‘Pos, Neg, or inconclusive’ is entered. Midwives are responsible for checking all blood requests.
The result is returned to the midwife via the hospital diagnostic test request and results system which is checked by the community midwife at the 16 week community appointment. In addition the screening coordinator monitors results via a central database and a letter is sent to the patient with the result.
Results and evaluation
To date we have had 95 RH negative women deliver following the implementation of FFDNA screening. Out of these 95 women, 10 women were issued a result of inconclusive of which 9 have had confirmation of a rhesus-positive baby. 40 negative results which have all been confirmed at delivery, and 41 positive results. Out of the 41 positive results we have had 1 negative baby incorrectly reported from the screening, two babies who are yet to be confirmed and 2 ladies have delivered elsewhere.
We were predicted to have 40% of women have a negative result and from the 95 women delivered we have had 42% of women receive a negative result which is better than predicted by 2%, however this is a small sample size and as our data grows this may change.
Patient feedback gained when the test is explained to women is that most women see the test as a positive change as they have a chance of not needing AntiD. They also feel that having the test done with their screening bloods is an advantage as they do not need to give an extra blood sample at a later appointment.
Key learning points
- Provide an information pack to each midwife and incorporate refresher training into existing annual training. Prioritise staff groups in order to target training appropriately.
- Consider offering the test at 12 weeks if there is central first trimester screening process in place as less staff are required to be trained to do it. This also means the same number of blood tests taken during pregnancy for most women, as it is incorporated in the taking of the Trisomy screening blood tests.