August 4, 2011 (Birmingham, United Kingdom) — In one of the largest studies of its kind, UK researchers have demonstrated that pulse-oximetry testing of newborn babies improves the detection of critical congenital heart disease, identifying defects that go undetected with antenatal ultrasound .
"Pulse oximetry is a better, more sensitive test than antenatal ultrasound and physical exam, although we are not suggesting we should replace those, but rather include pulse-ox as an additional screening tool, which would allow us to identify the majority of babies with critical congenital heart disease," lead author Dr Andrew K Ewer (University of Birmingham, UK) told heartwire .
Pulse-ox as an additional screening tool would allow us to identify the majority of babies with critical congenital heart disease."In addition, using pulse-ox, we identified a large number of babies who had other, serious, potentially life-threatening conditions, who would otherwise have been perceived to be well, and that was a bonus," he noted.
The report is published online August 4, 2011 in the Lancet.
In an accompanying comment, Dr William Mahle (Children's Healthcare of Atlanta and Emory University School of Medicine, GA) and Dr Robert Koppel (Cohen Children's Medical Center, New York, NY) say, on balance, they agree with the British team's conclusion. "The compelling data provided by Ewer and colleagues support inclusion of pulse oximetry into the care of the newborn baby," they state.
One of the Largest Studies, Including 20,000 Newborns
The percentage of congenital heart disease detected by antenatal ultrasound screening in developed nations varies. In the UK, around 50% of congenital heart disease is detected in this way, whereas in the US the figure has been put at around 25%, and in Sweden, one report showed detection was as low as 3%, Ewer said. There are a number of reasons for the differing figures, he explained, including the skill of the ultrasound operator and the size of the mother (it is often harder to spot problems in obese women).
Consequently, there is always a diagnostic gap, and many babies with congenital heart disease, and most important, those with critical congenital heart disease, will be missed after birth, a problem that is compounded by ever quicker discharge of new mothers from the hospital, says Ewer.
Pulse-oximetry screening is painless, inexpensive, and, Ewer believes, cost-effective, "because we would be picking up babies before they become unwell, and that makes their outcome better and their chances of success at surgery will improve."
Currently, use of pulse-ox screening is patchy at best in the UK, he says, with only about 6% of newborns tested in this way. And in Sweden, where a lot of research on pulse-ox has also been performed, there is as yet no national recommendation to include this test in postnatal screening for babies, he notes. In the US, New Jersey recently became the first state to mandate that every neonate be tested for congenital heart disease using pulse-ox, and other states are set to follow.
Although there have been a number of studies that examined pulse-ox and outcomes, they have generally been small, Ewer noted, and a key difference with this study is that babies who had been identified as having congenital heart disease on antenatal screening were included, a group usually excluded from trials.
In their study, Ewer and colleagues prospectively assessed the sensitivity and specificity of the pulse-ox test to detect critical congenital heart disease--defined as that causing death or requiring invasive intervention before 28 days--or major congenital heart disease (causing death or requiring invasive intervention before 12 months of age).
Between February 2008 and January 2009, 20 055 apparently healthy newborn babies from six maternity units across the UK were screened with pulse oximetry--which employs a noninvasive probe with two measurements taken on the upper and lower limbs and repeated to reduce false-positive rates--before discharge from the hospital and were followed up to 12 months of age.
Ewer says the fact that the babies included in the study had to appear healthy was key. "The acid test was, 'Would you have sent this baby home?' These were babies who were for all intents and purposes healthy, but some had low O2 sats. No one can clinically pick up babies who are very mildly cyanosed."
A Safe, Feasible Test That Adds Value to Existing Screening
Of the babies, 53 had major congenital heart disease (24 critical), a prevalence of 2.6 per 1000 live births. Pulse oximetry detected 75% of critical cases and 49% of all major congenital heart defects.
After excluding the 35 cases of suspected congenital heart defects following antenatal ultrasound, the specificity dropped to 58% for critical cases and 28% for all major cases.
Of the 35 cases already detected by antenatal ultrasound, all but one was also picked up by pulse-ox, Ewer said. "We knew babies had been identified antenatally, but if they hadn't, we wanted to know, 'Would they have been picked up by pulse-ox?' We missed out on one."
When pulse-ox was combined with routine ultrasound and newborn physical examination, "We were able to improve detection to 92% of babies with critical congenital heart disease, which is not perfect, but it's much better than we are doing at the moment," he added.
"Pulse-ox is a safe, feasible test that adds value to existing screening," he and his colleagues conclude.
In their commentary, Mahle and Koppel say the reported sensitivity and specificity of pulse oximetry in this UK population are "reasonable and in keeping with the results of studies from Europe and North America."
But Is It Cost-Effective?
In the study, false-positive results were noted for 169 (0.8%) of babies (specificity 99.16%), of which six cases were significant, but not major, congenital heart defects, and 40 were other illnesses that required urgent medical intervention.
Ewer says one of the complaints of critics of pulse-ox screening has been the cost of echocardiography in the false-positive cases, but he noted that "in our unit, we have in-house echo, and in fact echo is not necessarily always required. We don't echo every baby who fails a pulse-ox test. We use very careful, clinical assessment by a senior clinician, and sometimes we wait and watch," because low oxygen levels can just be due to the transitional circulation of a newborn and will improve with time.
He says his team also did a cost-effectiveness analysis, not included in the Lancet paper, and came out with a "worse-case-scenario" figure--where every baby who failed the pulse-ox got an echo, and the pulse-ox was performed by a midwife (in reality it can be done by a healthcare assistant)--of £24 000 per timely diagnosis of critical congenital heart disease, "so it seems to be cost-effective, in our opinion."
The actual cost of the test per baby, pegged by Mahle and Koppel in their comment at around $1 per infant when performed by a technician, is "a drop in the ocean" in healthcare terms, says Ewer. "To me, it's a no-brainer, but then I don't have to pay for it." Ewer is now hoping, with these data, to convince the UK National Screening Committee to endorse pulse-ox screening as routine for newborns in the UK.
In their comment, Mahle and Koppel go on to debate the pros and cons of adding pulse-ox tests to routine screening of newborns, eventually concluding that, "occasionally, the results of one large randomized trial can abruptly change medical practice. More often, the decision to steer a new course is supported with results from a series of studies, all with some limitations. The work of Ewer in the UK, Granelli in Sweden, and several others has brought us to the threshold of such a decision."