It is now several years since the first study of using pulse oximeters to screen for congenital heart disease were published. The initial response was a little skeptical, and appropriately cautious. It was immediately clear that there would be numerous false positives (which is common in universal screening programs) but also false negatives (which need to be minimized in screening to make it worthwhile). Also, and in contrast with some other screening programs, numerous children were already being diagnosed, either in utero by ultrasound or by routine neonatal exam.
The purpose of the screening program then, is to detect children who are not otherwise being diagnosed, and who are at risk of serious health consequences if undetected. This mostly occurs in infants who have ductus dependent conditions, such as pulmonary atresia and interrupted aortic arch. The cyanotic forms should be readily detectable with pulse oximetry screening. But even the acyanotic forms may have right to left ductal shunting with reduced saturations in the feet, despite normal saturation in the right hand.
So costs and benefits need to be weighed carefully, “are the numbers of children detected by routine pulse oximetry, and who would then avoid an early post-discharge collapse at home and therefore have a better chance of surviving and doing well long-term, sufficient to justify the costs, and the stress caused to parents by a false positive screen?”.
A new systematic review in the lancet included 13 studies with over a quarter of a million babies. Thangaratinam S, Brown K, Zamora J, Khan KS, Ewer AK: Pulse oximetry screening for critical congenital heart defects in asymptomatic newborn babies: a systematic review and meta-analysis. Lancet 2012(0). http://www.sciencedirect.com/science/article/pii/S014067361260107X
This review confirmed what I felt was already clear 3 years ago, Barrington KJ: Neonatal screening for life threatening congenital heart disease. BMJ 2009, 338:a2663. http://www.bmj.com/content/338/bmj.a2663?view=long&pmid=19131381 There is sufficient evidence of efficacy, and sufficiently low false positives (they can be reduced to 0.05% if the screening is performed after 24 hours of age) to institute universal screening.
The remaining questions need to be addressed, should we screen just one foot, or follow with the right hand under certain circumstances? Which precise saturation threshold should be used? How will parents who have a false positive screening test, but a normal echocardiogram react? Is it cost-effective? The last two questions have also been addressed by Andrew Ewer and his coworkers.
Powell R, Pattison HM, Bhoyar A, Furmston AT, Middleton LJ, Daniels JP, Ewer AK: Pulse oximetry screening for congenital heart defects in newborn infants: an evaluation of acceptability to mothers. Archives of Disease in Childhood – Fetal and Neonatal Edition 2012. http://fn.bmj.com/content/early/2012/05/17/fetalneonatal-2011-301225
Roberts TE, Barton PM, Auguste PE, Middleton LJ, Furmston AT, Ewer AK: Pulse oximetry as a screening test for congenital heart defects in newborn infants: a cost-effectiveness analysis. Archives of Disease in Childhood 2012, 97(3):221-226.
These studies showed that screening was very well accepted by parents, even those who experienced a false positive. Interestingly this was also previously shown for false positives during neonatal hearing screening, and I think shows that when parents are well-informed, they are capable of understanding false positives, and appreciate the fact that the universal screening is designed to help the true positives. Also, in this case, the false positives have had a cardiac echo and can be very confident that their babies heart is fine. In addition in most studies there are some of the supposed “false positives” that actually have an important diagnosis and are aided by the test.
The cost effectiveness analysis came up with a cost of around 20000 pounds sterling per critical congenital heart disease detected. Many undetected cases present with serious illness, and have an increase in long-term morbidity or mortality. So the benefits are significant, and the costs are relatively modest and in line with other neonatal screening programs.
In terms of the details of technique, a threshold of 94, 95, or 96% has been used, with some studies adding a difference between leg and right hand, (such as a >3%) difference, which would mean that if the leg was 95, or 96% then the hand would be measured as well, but if the leg was 97% no further testing would be required, and if less than 95% then an echocardiogram is required whatever the hand shows.
If you combine the information in the Supplemental Table from the new meta-analysis published in the lancet with the information in the Table in the print version, it seems that a threshold of 96%, i.e. 96% and above is fine, 95% and below requires further testing, increases sensitivity compared to a 95% threshold with very little effect on the false positives.
Again among the large studies it doesn’t seem that adding the right hand saturation adds much in terms of sensitivity, but also does not seem to affect false positives. It does significantly prolong and complicate the process.
Adding universal pulse oximetry screening in the second 24 hours of life to other screening programs appears to be acceptable to parents, as cost-effective as other neonatal screening programs, widely applicable, and could prevent death, morbidity and disability.