Incidence and detection rate

The observed rate of critical CHD in our study, as indicated by positive cases among the screened population, corresponds to a prevalence rate of approximately 24.2 per 1000 live births. This finding is higher than the international estimates, which suggest a critical CHD incidence of around 2–3 per 1000 live births. ^{Reference Liske, Greeley and Law12,Reference Majani, Chillo and Slieker13} This higher rate could be explained by the increased rate of delivery in some areas, especially in Upper Egypt, as well as the nature of the involved centres which are all tertiary centres receiving mostly the critical cases. It could be also a reflection of a real increased incidence of CHD in Egypt. Moreover, this prevalence is hospital-based. It is not possible to derive a true population-based prevalence of critical CHD from a hospital-based study. The reported prevalence in our study is reflective of the characteristics and demographics of the population within the university hospitals and does not necessarily represent the broader, general population of Egypt.

It is important to note that the implementation of pulse-oximetry screening could increase the detection rate of critical CHD cases that might be missed by clinical examination alone. ^{Reference Barreto14} Critical CHD is responsible for more deaths than any other type of malformation. ^{Reference Hoffman and Kaplan15,Reference Reller, Strickland, Riehle-Colarusso, Mahle and Correa16} Some cases are detected by a prenatal ultrasound; others may be detected based on clinical findings (e.g., heart murmurs, tachypnea, respiratory distress, or cyanosis) in the newborn; however, about 30–50% of infants with critical CHD are discharged after birth without being diagnosed resulting in significant morbidity or mortality. ^{Reference Kumar17}

Birth weight of the included neonates

In our cohort, 43.1% of screened newborns had a birth weight < 2,000 g. The high percentage of newborns with low birth weight in our study can be explained by the inclusion of late preterm neonates. Our study included neonates born at ≥ 35 weeks of gestation, which encompasses late preterm infants who may have lower birth weights compared to full-term infants. Late preterm neonates are at higher risk for various health issues, including CHD, and this may contribute to a higher representation of lower birth weight infants in our cohort. In addition, the hospitals involved in the study were tertiary care centres, which often serve populations with higher rates of low birth weight infants, such as those born to mothers with pre-existing health conditions or complications. This could further explain the higher proportion of low birth weight infants in our sample.

Early identification and intervention

Pulse-oximetry screening has a major advantage in detecting cases of critical CHD during the early postnatal period. This early identification enables timely intervention and management, which can significantly improve the prognosis and outcomes for affected infants. ^{Reference Kumar17} . Our study underscores the importance of establishing a standardised screening programme to ensure the prompt and proper diagnosis and management of critical CHD.

False positives and specificity

Although pulse-oximetry screening is a useful method for detecting critical CHD in infants, it comes with certain challenges. One of the potential limitations of this screening is the chance of false-positive results. These can occur due to various factors, such as temporary oxygen desaturation and other non-cardiac conditions. Furthermore, screening before 24 hours of birth may lead to a higher number of false-positive results. ^{Reference Kluckow18} It is important to interpret screening results with sensitivity and specificity to avoid unnecessary parental distress or diagnostic procedures for non-critical CHD cases. ^{Reference Plana, Zamora, Suresh, Fernandez-Pineda, Thangaratinam and Ewer19} . However, even in cases of false positives, the chance of saving non-cardiac critical cases could be also achieved with pulse-oximetry screening.

The higher false-positive rate in our study may be a result of a more heterogeneous population with various risk factors, including low birth weight and late preterm births. The timing of screening (within the first 24–72 hours of life), the specific devices used, and variations in clinical practices across the different hospitals could all contribute to differences in the false-positive rate. Besides, in low-resource settings or in certain populations, there may be increased environmental or clinical factors that affect the performance of pulse-oximetry, leading to higher rates of false positives. Factors such as respiratory infections, ambient temperature, or the use of supplemental oxygen might lead to oxygen saturation values that are outside the threshold, even in the absence of critical CHD.

Other measurements other than oxygen saturation have been suggested as possible screening tools to improve critical CHD detection, especially the coarctation of the aorta. Adding photoplethysmography parameters would improve critical CHD detection more than using pulse-oximetry alone. ^{Reference Siefkes, Kair, Tancredi, Vasquez, Garcia, Bedford-Mu and Lakshminrusimha20,Reference Siefkes, Oliveira and Koppel21}

Resource implications

When implementing pulse-oximetry screening in healthcare, it is important to consider the necessary resources, such as equipment, training, and personnel. ^{Reference Bradshaw, Cuzzi, Kiernan, Nagel, Becker and Martin22} Although our study proves the effectiveness of pulse-oximetry screening, we need to conduct further research to examine the cost-effectiveness and the ability to expand this approach within the Egyptian healthcare system. This will ensure its sustainability in the long run. In addition, pulse-oximetry is a low-cost non-invasive screening method and could minimise the abuse of high-cost echocardiography requested by the paediatrician for negative cases.

Pulse-oximetry screening might decrease the exhaustion of other expensive diagnostic tools such as echocardiography and MRI that should be directed only to the suspected cases of critical CHD. Indeed those tools are essential in the diagnosis of many CHD; ^{Reference Sakrana, Al-Zubaidi, Nasr, Helmy, Al Ghamdi and Tahlawi23} however, their use should be limited to positive cases.

In addition, we should emphasises the importance of comprehensive monitoring techniques beyond pulse-oximetry alone; integrating quantitative assessments such as CMR and echocardiography could enhance our understanding of long-term outcomes in neonates diagnosed with critical CHD, thereby informing clinical management strategies. ^{Reference Tissot and Singh24,Reference Sakrana, Abdel Razek, Yousef, El Tahlawi and Gadelhak25}

The use of pulse-oximetry screening could also save resources by early intervention and preparation of the required tools before the procedures needed for critical cases. ^{Reference El Tahlawi, Bonello and Fraisse26}

Therefore, pulse-oximetry could be an efficient tool for detecting critical CHD in low-income countries and limited-resource sites.

Despite low cost, pulse-oximetry is also considered an effective tool in high-income countries. ^{Reference Lannering, Kazamia and Bergman27,Reference Sakai-Bizmark, Chang and Martin28}

Challenges and future directions

As the first study of its kind in Egypt, our research serves as a foundation for further investigations into the long-term outcomes of infants with critical CHD detected through pulse-oximetry screening. Future studies should explore the impact of early diagnosis on morbidity and mortality rates, as well as the potential economic benefits of early intervention.

Additionally, healthcare providers, parents, and caregivers should be educated about the importance of critical CHD screening and its life-saving benefits. ^{Reference Bradshaw, Cuzzi, Kiernan, Nagel, Becker and Martin22} Establishing standardised protocols and guidelines for pulse-oximetry screening in Egypt will further contribute to its successful implementation and integration into routine newborn care.