Objective. To determine the sensitivity, specificity, predictive value, and accuracy of a program of pulse oximetry screening of asymptomatic newborns for critical congenital cardiovascular malformation (CCVM).
Methods. Pulse oximetry was performed on asymptomatic newborns in the well-infant nurseries of 2 hospitals. Cardiac ultrasound was performed on infants with positive screens (saturation ≤95% at >24 hours). Data regarding true and false positives as well as negatives were collected and analyzed.
Results. Oximetry was performed on 11 281 asymptomatic newborns, and 3 cases of CCVM were detected (total anomalous pulmonary venous return ×2, truncus arteriosus). During the study interval, there were 9 live births of infants with CCVM from a group of 15 fetuses with CCVM detected by fetal echocardiography. Six infants with CCVM were symptomatic before screening. There was 1 false-positive screen. Two infants with negative screens were readmitted (coarctation, hypoplastic left pulmonary artery with aorto-pulmonary collaterals). Other cardiac diagnoses in the database search were nonurgent, including cases of patent foramen ovale, peripheral pulmonic stenosis, and ventricular septal defect. The prevalence of critical CCVM among all live births was 1 in 564 and among the screened population was 1 in 2256 (sensitivity: 60%; specificity: 99.95%; positive predictive value: 75%; negative predictive value: 99.98%; accuracy: 99.97%).
Conclusions. This screening test is simple, noninvasive, and inexpensive and can be administered in conjunction with state-mandated screening. The false-negative screen patients had lesions not amenable to detection by oximetry. The sensitivity, specificity, and predictive value in this population are satisfactory, indicating that screening should be applied to larger populations, particularly where lower rates of fetal detection result in increased CCVM prevalence in asymptomatic newborns.
Comments
Re: Screening of CHD: clinicians vs. pulse oximetry
We thank Dr. Harkavy for his interest in our article. He has made several interesting observations to which we will respond.
Our intention in conducting our study was to evaluate the effectiveness of pulse oximetry as a screening test to detect serious cardiac malformations at a time-point prior to discharge. In practice, the most convenient time for such screening would be on admission to the nursery. However, we were concerned that screening at that time-point would result in a high false positive rate due to physiologic right-to- left ductal shunting. While a standardized time-point would have been preferable, each hospital decided when to screen based on existing nursery routines and practices.
We reported two cases of false negative screens, one at each participating hospital. The hospital of birth, though not mentioned in the text, is summarized in table 2. On the basis of the limited population of our study, we can report a screening detection rate of 1/3760. Using the figure of 1/8642 would still make the yield of this screening test higher than almost all conditions for which newborn screening is currently performed. The purpose of the screening test was not to identify infants prior to the onset of clinical signs but rather, to prevent infants at risk for cardiovascular collapse from going home without a diagnosis. Careful evaluation by pediatric staff was not an important difference between the two sites as the presenting signs of the infants that were symptomatic prior to screening were not subtle.
With respect to the cost of this screening, the nurses providing the routine newborn care in the well-baby nurseries performed the oximetry. The average time required to place the Velcro wrap-around oximeter probe on the infant’s foot, allow the infant to settle, and obtain a stable waveform was approximately one minute. The reusable probes are swabbed with alcohol between patients and are considered by infection control to be analogous to blood pressure cuffs that are placed in direct contact with clean, unbroken skin on multiple patients.
D. Harkavy correctly points out that none of the types of cardiovascular malformations detected by fetal echocardiography in our series were represented in the group of infants that were asymptomatic after birth; nevertheless, these cardiac malformations are well known to potentially be asymptomatic until after discharge. What we can state with respect to the patients in our series is that two infants with TAPVR and one infant with truncus arteriosus that were not suspected during fetal life and were asymptomatic in the nursery were detected by oximetry screening.
Oximetry screening satisfies the requirements for a screening test because of the risk of death or CNS injury if diagnosis is delayed. We agree that future studies should carefully examine the long term cardiovascular and neurodevelopmental outcomes of infants with cardiovascular malformations, regardless of the method of detection. However, this matter was beyond the scope of our pilot project. As stated in the article, oximetry screening is not intended to serve as a substitute for a careful physical examination. We believe that oximetry screening represents an inexpensive, non-invasive method that can enhance the clinician’s ability to detect life-threatening illness in a timely manner.
Screening of CHD: clinicians vs. pulse oximetry
Sirs :
Drs. Koppel et al (1) present an interesting approach to the identification of " critical " congenital cardiovascular malformations (CCVM). They use pulse oximetry at either the time of discharge (Hospital B or " B ") or mandated metabolic screen (Hospital A or " A "). The average age at screening at B was 57 hours for vaginal delivery. The average for A is not given, only that screening occurs after 24 hours of age. Based my experience, metabolic screening usually occurs 24 to 48 hours after birth for vaginal deliveries. Given that time of birth is random, the average time of screening at A would be 36 hours, or almost 24 hours earlier than B. Also missing are the location of birth for the two affected infants not identified via screening.
I am surprised that the prevalence of asymptomatic CCVM is 5 time higher at B than at A. Given the older screening age at B, I would have expected more CCVM to become symptomatic before screening. At A, 4 of 5 were identified by examination. This could have been as low as 4 of 7 if the missed babies were born at A. At B, 2 of 4 (or as low as 2 in 6) were identified by examination. Is there an explanation to be found in the nature of the two hospitals ? A had more deliveries, and based on fetal echocardiography, appears to be a referral center. Perhaps the incidence of 1 in 8642 asymptomatic infants at A, not 1 in 1320 at B, is the more appropriate incidence figure to use after careful evaluation by the pediatric staff.
A second issue is the description of cost as "negligible." There is no mention of the time taken to do the screening or the level of skill and pay rate of the screener. The cost of the saturation probes is not identified. Is the same probe being used for multiple patients ? Is this an infection control issue ?
In the discussion, the authors suggest that " screening should be applied to larger populations, particularly where lower rates of fetal detection result in increased CCVM prevalence in asymptomatic newborns. " Why do the authors think that the types of CCVM they report from fetal screening would be asymptomatic ? None of the similar ones identified after birth were asymptomatic.
Lastly, screening programs choose to screen for diseases that are silent early in life, that lead to irreversible damage if undetected, and where treatment prevents damage. Do these criteria hold true for the clinically missed CCHD ? The authors should report the outcomes of the patients identified by screening and compare them to the outcomes of those identified by clinical exam before and after discharge. If the outcomes are the same, then screening has not added to the care of the infant. Because you can doesn't mean you should.
1. Koppel RI, Druschel CM, Carter T, et al. Effectiveness of pulse oximetry screening for congenital heart disease in asymptomatic newborns. Pediatrics 2003;111: 451-455.
Re: The Cost of Newborn Hearing Screening
We thank Dr. Grosse for correctly identifying a typographical error in table 5 and for providing a more current estimate of the cost of case finding by universal hearing screening. We apologize for the error in our manuscript. In terms of cost, pulse oximetry screening for critical cardiovascular malformations continues to compare favorably with the other tests in the current newborn screening panel.
The Cost of Newborn Hearing Screening
Table 5 in this article contains a typographical error. The cost per case of hearing loss detected, based on Colorado estimates, should have been $9,600, not $98,600(1). A more recent estimate of the cost of detection with universal newborn hearing screening compared to the cost of detection without screening is $21,400 per child with hearing loss diagnosed by 6 months of age (2).
1. Mehl AL, Thomson V. Newborn hearing screening: the great omission. Pediatrics.1998; 101(1) . Available at: www.pediatrics.org/cgi/content/full/101/1/e4 2. Keren R, Helfand M, Homer C, McPhillips H, Lieu TA. Projected cost- effectiveness of statewide universal newborn hearing screening. Pediatrics. 2002;110(5):855-64.