NIHR Signal Testing oxygen levels of newborn babies helps find serious heart defects
Published on 17 July 2018
Measuring oxygen levels in newborn babies as part of routine care can identify cases of critical congenital heart defects sooner than waiting until symptoms appear. If 10,000 babies were screened, pulse oximetry could correctly identify about 5 of the 6 expected asymptomatic cases and might miss one. This international research suggests there would be about 14 false alarms. Waiting until babies are at least 24 hours old minimises the number of these false positives.
Babies with critical heart defects often show no symptoms at birth. Early detection of these problems increases the chance of successful treatment. This systematic review looked at 21 studies of 457,202 babies where pulse oximetry (measuring the amount of oxygen in the blood using a device put on the hand or foot) was used as a simple screening test.
Pulse oximetry correctly identifies 76.3% of babies who have critical congenital heart defects. It also correctly identifies 99.9% of healthy babies without problems.
Current UK newborn screening programmes do not include pulse oximetry because a national pilot scheme suggested there would be higher false positive results in routine NHS practice.
- Cardiovascular system disorders, Neonates and neonatal care, Screening, Midwifery
Why was this study needed?
Incidence estimates for critical congenital heart defects (CCHD) vary. Only 50% of these defects are detected before birth. The remaining babies with CCHD may not show any symptoms in the period immediately after birth. Up to 30% of babies born with CCHD are discharged home before these are detected, which can lead to mortality of up to 50%. Earlier treatment of CCHD tends to lead to better outcomes, so detection before discharge is important.
Existing methods of screening for CCHD, such as antenatal ultrasound or postnatal clinical examination, are inconsistent at detecting defects and may miss cases. Therefore, additional approaches to screening are needed to find cases more efficiently.
What did this study do?
This systematic review looked at studies of pulse oximetry in newborn infants without symptoms or signs. All studies involved infants who were born at or near full term, before being discharged from hospital.
Critical congenital heart defects were defined as any condition involving duct-dependent heart lesions which were potentially life-threatening, requiring invasive intervention within 28 days of birth.
All pulse oximetry measurement approaches were included, whether measurements were taken from hands, or feet or both.
To assess diagnostic accuracy, the reference standard comparators were diagnostic echocardiography, and clinical follow up in the first 28 days of life. This included post-mortem findings and data stored in databases of congenital defects.
The included studies were assessed for risk of bias and overall reliability using well-known checklists. The low certainty evidence for the test sensitivity estimate suggests further research and pilots are required.
What did it find?
- Of the 21 studies included (457,202 participants), 19 studies (436,758 participants) provided data for the primary outcome of CCHD of oxygen saturation of less than or equal to 95%. Five studies were from the UK, and the remainder were all from high or middle-income countries, suggesting that they are relevant.
- Using this threshold, 76.3% of cases were correctly identified (95% confidence interval [CI] 69.5 to 82.0%; low certainty evidence of test sensitivity). Of the infants without CCHD, 99.9% were correctly identified (95% CI 99.7 to 99.9%; high certainty evidence of test specificity).
- Delaying pulse oximetry to more than 24 hours after birth reduced the rate of false positive CCHD detection. Studies carrying out the measurement within 24 hours had a false positive rate of 0.42% (95% CI 0.20 to 0.89%) compared with a rate of 0.06% (95% CI 0.03 to 0.13%) in studies where measurement was performed more than 24 hours after birth.
- If these results were replicated in NHS practice, of 10,000 apparently healthy near or full-term births, pulse oximetry would correctly identify 5 of the 6 likely cases of CCHD and lead to 14 other babies without CCHD having further investigations.
What does current guidance say on this issue?
UK guidance on screening for congenital heart defects is described in Public Health England’s Newborn and infant physical examination screening programme handbook (2018). This screening is part of the newborn, and infant physical examination recommended for all babies within 72 hours of birth, with a follow up at 6 to 8 weeks.
Pulse oximetry is not currently included in the range of investigations. The guidance notes that the results of the national newborn pulse oximetry pilot study may lead to related cardiac standards being added to this guidance.
What are the implications?
This study provides evidence which has been considered in reviews of the current newborn screening programmes. Pulse oximetry is a fast and non-invasive method to detect CCHD in babies who are not symptomatic.
Incorrect identification of potential CCHD cases may cause anxiety for parents and delay discharge from hospital while further investigations are carried out. False positive rates can be reduced by delaying screening until more than 24 hours after birth, though this may have practical limitations if aiming to discharge newborns more promptly.
Further investigation of the optimal pulse oximetry protocol and its delivery in practice may lead to further guidance.
Citation and Funding
Plana MN, Zamora J, Suresh G, et al. Pulse oximetry screening for critical congenital heart defects. Cochrane Database Syst Rev. 2018;(3):CD011912.
This project was funded by the Instituto Ramón y Cajal de Investigaciones Sanitarias, the Universidad Rey Juan Carlos, and the CIBER Epidemiology and Public Heath, Spain. The Cochrane Neonatal Review Group was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (National Institutes of Health).
NHS Choices. Newborn physical examination. London: Department of Health and Social Care; updated 2018.
NHS Choices. Congenital heart disease. London: Department of Health and Social Care; updated 2018.
PHE. Guidance: Newborn and infant physical examination screening programme handbook. London: Public Health England; updated 2018.
Using pulse oximetry as a tool to detect life-threatening conditions - not solely congenital heart disease - in newborn babies is common practice in England. Approximately half of maternity units are using it, though delivery models vary.
Recent National Screening Committee screening pilots showed higher false positive rates than this review, albeit of clinically important findings. A key difference is that testing was performed within 12 hours although the review found greatest specificity if testing is after 24 hours; a challenge to delivery with early discharges.
Establishing the optimal pathway for those testing positive should, therefore, be a focus of future investigation.
Rhosyn Harris, Public Health Registrar (ST4), Oxford School of Public Health; Allison Streetly, Senior Lecturer, Kings College London
Pulse oximetry is a test to measure how much oxygen is in the blood. It involves a sensor being placed on a finger or a toe. No blood sample is taken during the measurement.