Our review has identified pulse oximetry as a potentially useful screening test for congenital heart disease in asymptomatic newborns. Pulse oximetry is a non‐invasive, readily available, relatively cheap, well‐validated test currently carried out by either a nurse or a doctor.1
Published individual studies have lacked the large numbers of patients necessary to confidently estimate the accuracy of the test. Our review and meta‐analysis have tried to address this issue by collating the results of published studies.
The high specificity reflects the low false positive rate of this test. The highly specific nature of the test also signifies that a low pulse oximetry reading in asymptomatic newborns “rules in” congenital heart disease until proved otherwise.27 The sensitivity of the test, however, is varied, with wide confidence intervals that may be attributed to the low prevalence of the condition. This is best seen in Figure 3A, in which the confidence ellipse displays a narrow specificity axis, a reflection of the consistency in the specificity observed across all studies. The wider sensitivity axis is an indication of the reduced confidence we have in the accuracy of its sensitivity.
The validity of the findings of our review is dependent on the methodology of the systematic review and the quality of the individual studies included.19
An extensive literature search was performed using relevant databases without any language restrictions to minimise the possibility of missing any study. The quality of most of the studies was compromised due to the differential verification by either echocardiography (in test positive cases) or clinical follow‐up (test negative) cases. Perhaps this is unavoidable. Two of the included studies were case–control studies, a design that biases the results by overestimating the diagnostic odds ratio.22
Furthermore, the absence of blinding, and absent or poor description of the test or reference standard could have affected the results of the review. The significant heterogeneity observed in the results could be a reflection of the type of saturation chosen for the cut‐off level (functional v
fractional), method of testing and the inclusion or exclusion of newborns diagnosed as having congenital heart disease antenatally, thereby leading to a spectrum of variation. None of the studies evaluated acceptability of “babies” testing to parents and the psychosocial impact of false positive results or identification of non‐critical congenital heart disease.
What is already known on this topic
- Congenital heart diseases in newborns if identified early can be successfully treated.
- Clinical examination of newborns for murmurs and cardiovascular function does not have good detection rate. As a result many babies present with complications after discharge from hospital.
- There is currently no effective screening tool for this condition.
- Pulse oximetry can pick up desaturation of blood objectively.
We used a bivariate analysis model for meta‐analysis with a random effects approach to obtain summary estimates of both sensitivity and specificity. This model accounts for the heterogeneity between studies caused by different threshold settings. In addition, the model acknowledges the difference in precision by which sensitivity and specificity have been measured in each study. This means that studies with larger numbers of patients with the target condition receive more weight in the calculation of the summary estimate of sensitivity, whereas studies with more patients without the target condition are more influential in the pooling of specificity. The model accounts also for the residual heterogeneity due to clinical or methodological differences between studies. Unfortunately, we could not perform an explicit analysis of these potential sources of heterogeneity due to the limited number of studies included in our review.
Given the rarity of the outcome—that is, congenital heart disease in the general population—large, well‐conducted and robust studies are essential to confirm the value of pulse oximetry as a screening test, in isolation or in combination with clinical examination to obtain precise estimates of its sensitivity. Further research is needed to evaluate the effect of screening on parents and its acceptability to parents and healthcare professionals, especially with the possibility of non‐significant lesions being detected during echocardiography, and the costs and cost‐effectiveness of the screening programme for healthcare services.
What this study adds
- Pulse oximetry is highly specific for detecting congenital heart disease.
- Current estimates of sensitivity to detect congenital heart disease are imprecise.
- This is a promising technique that needs large, well‐conducted studies to assess the accuracy, effectiveness and feasibility of its use for mass screening of congenital heart disease in newborns.