Positive predictive value of pulse oximetry in the screening of critical congenital heart defects in term neonates

Abstract

Background: Critical congenital heart defects (CCHD) are associated with poor patient outcome due to delay in diagnosis. Clinical examination alone has low positive predictive value (PPV). Pulse oximetry examination is suggested as supplemental screening tool. Aim of this study was to screen term neonates for CCHD by clinical and pulse oximetry evaluations and estimate their PPV separately and combined.Methods:Cross-sectional study of 278 term neonates weighing ≥2500g excluding those with antenatal diagnosis of congenital heart defects and/or requiring intensive care. Sample size calculated using EpiInfo version 7 taking 20,000 as population size, 7% expected frequency, 5% confidence limits and 99.9% confidence level. Ethical clearance and informed consent obtained. Clinical examination was performed within 24 hours of life followed by pre-ductal and post-ductal oxygen saturation (SpO2) recording, using standardized hand-held probe, between 24-48 hours. Neonates categorized as screen positive or negative based on an adapted algorithm. Screen positives were confirmed by echocardiography. SPSS version 16 was used for statistical analysis.Results: Mean age at clinical examination was 7.72 ± 0.32 hours during which none screened positive. Mean age at SpO2 screening was 31.93 ± 0.32 hours and a single non-syndromic, acyanotic male newborn, weighing 2550g screened positive. He was found to have severe pulmonary outflow obstruction, with ductus-dependent flow on echocardiography. PPV for pulse oximetry screening alone was 100%.Conclusions:Ductus dependent lesions missed on clinical examination may be picked up by pulse oximetry screening. Echocardiography may be used selectively to confirm diagnosis on screen positive.