Am Fam Physician. 2019;99(7):421-422
Author disclosure: No relevant financial affiliations.
Is pulse oximetry a diagnostically accurate screening test for critical congenital heart defects in newborns?
Pulse oximetry is an accurate screening test for critical congenital heart defects in newborns. Pulse oximetry is simple to use, widely available, and has moderate sensitivity (76.3%) and good specificity (99.9%). However, the prevalence of critical congenital heart defects is low, and most newborns who screen positive do not have a critical congenital heart defect.1 (Strength of Recommendation: B, based on limited-quality patient-oriented evidence.)
Congenital heart defects occur in approximately 1% of live births in the United States. About 25% of those newborns are considered to have a critical congenital heart defect.2 Mortality rates vary by the exact diagnosis but range as high as 30% and are likely decreased with early detection.3,4 Because most critical congenital heart defects are amenable to treatment, and newborns with these types of heart defects are usually asymptomatic, a good screening test may decrease mortality. The purpose of this Cochrane review was to determine the accuracy of pulse oximetry as a screening test for critical congenital heart defects.1
This Cochrane review examined 19 cohort and cross-sectional studies of low to moderate quality with 436,758 asymptomatic term or late preterm newborns who received screening in a newborn nursery setting.1 Newborns who were screened at home or in the neonatal intensive care unit were excluded from the review. The studies were spread across 13 countries, with only two from the United States. Each of the studies in the United States included a cohort of approximately 10,000 to 15,000 newborns and lacked adequate follow-up.
Eleven studies measured oxygen saturation in the foot alone (postductal), and eight studies measured it in the hand and foot (preductal and postductal). Eight studies measured the oxygen saturation within 24 hours of life, and the others measured it after 24 hours of life. A positive screen was defined as an oxygen saturation of less than 95% in 14 studies and 95% or less in five studies. Echocardiography was subsequently performed in all infants who screened positive. Studies described clinical follow-up, a review of mortality or cardiology data, or no confirmation for newborns with negative screens.
The sensitivity of pulse oximetry for the detection of critical congenital heart defects was 76.3% (95% CI, 69.5 to 82.0), and the specificity was 99.9% (95% CI, 99.7 to 99.9). This review found that for every 10,000 asymptomatic term or late preterm newborns screened by pulse oximetry, five out of every six newborns with critical congenital heart defects will screen positive with an oxygen saturation of 95% or less, and there will be 14 false positives.
Currently, 48 states mandate routine screening for critical congenital heart defects in newborns.5 A recent article found that infant deaths caused by critical congenital heart defects decreased significantly in states that implemented mandatory screening policies during the study period (from 2007 to 2013).6 Nevertheless, there is the potential for false positives, which may lead to increased anxiety for parents.1 Physicians should be aware of the false-positive rate of this screening test when counseling parents after a positive screen.