Point-of-Care Bilirubin Testing in Neonates: Comparative Performance of Blood Gas Analysis and Transcutaneous Bilirubinometry

<b>Background</b>: Neonatal jaundice is a common condition with potentially severe complications such as bilirubin-induced neurological dysfunction and kernicterus. While serum bilirubin (SBR) remains the standard laboratory measurement, point-of-care methods, such as transcutaneous bilirubinometry (TcB) and blood gas analysers (BGAs), offer rapid, less invasive alternatives. Direct comparisons of their diagnostic accuracy remain limited. <b>Objective</b>: The aim of this study was to assess and compare diagnostic accuracy and clinical utility of TcB and BGA against SBR in neonatal hyperbilirubinaemia screening. <b>Methods</b>: This retrospective study included neonates (n = 221) with concurrent SBR, BGA, and TcB measurements (n = 333). Assessment was via Passing-Bablok regression, Bland-Altman analysis, and Spearman correlation. Diagnostic performance was evaluated against jaundice thresholds in phototherapy charts (≥95th percentile threshold). Subgroup analyses considered phototherapy status, haemoglobin concentration, and Fitzpatrick skin type. <b>Results</b>: BGA showed stronger agreement with SBR (R² = 0.88) than TcB (R² = 0.43). BGA remained accurate regardless of phototherapy or haemoglobin levels. TcB accuracy declined post-phototherapy with reduced predictive value in darker-skinned neonates (Fitzpatrick III-VI) and increased false discovery rates. Both methods demonstrated low sensitivity (45.8%) but high specificity (>95%) and negative predictive value (~91%) for clinically significant hyperbilirubinaemia. BGA had a higher diagnostic odds ratio (47.5) than TcB (19.3). When individual patient sequential SBR and BGA measurements were compared for jaundice tracking (n = 175), there was high correlation, (r = 0.971) with no statistical differences, and 50% of measurements achieving agreement within 10 μmol/L. <b>Conclusions</b>: BGA is a more reliable alternative to SBR than TcB, particularly in time-critical or resource-limited settings. While TcB remains a non-invasive screening tool, limited accuracy post-phototherapy and with darker skinned neonates indicate confirmatory SBR testing. These findings support the selective and context-aware use of BGA and TcB to optimise neonatal hyperbilirubinaemia management and reduce interventions.