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

## TL;DR

Blood gas analysers are more accurate than transcutaneous bilirubinometry for measuring bilirubin in newborns, especially after phototherapy or in darker-skinned infants.

## Contribution

This study directly compares blood gas analysers and transcutaneous bilirubinometry against lab measurements in neonates, revealing their performance differences in various clinical contexts.

## Key findings

- Blood gas analysers showed strong agreement with lab bilirubin (R2 = 0.88) compared to transcutaneous bilirubinometry (R2 = 0.43).
- Transcutaneous bilirubinometry accuracy dropped after phototherapy and in darker-skinned neonates (Fitzpatrick III–VI).
- Blood gas analysers had a higher diagnostic odds ratio (47.5) than transcutaneous bilirubinometry (19.3).

## Abstract

What are the main findings?
Blood gas analyser bilirubin showed stronger agreement with central laboratory serum bilirubin (R2 = 0.88) than transcutaneous bilirubinometry (R2 = 0.43), with blood gas analyser maintaining accuracy regardless of pre- vs. post-phototherapy or haemoglobin levels.Transcutaneous bilirubinometry accuracy significantly reduced post-phototherapy and showed reduced predictive value in darker-skinned neonates (Fitzpatrick III–VI), while the blood gas analyser demonstrated superior diagnostic performance with a diagnostic odds ratio of 47.5.

Blood gas analyser bilirubin showed stronger agreement with central laboratory serum bilirubin (R2 = 0.88) than transcutaneous bilirubinometry (R2 = 0.43), with blood gas analyser maintaining accuracy regardless of pre- vs. post-phototherapy or haemoglobin levels.

Transcutaneous bilirubinometry accuracy significantly reduced post-phototherapy and showed reduced predictive value in darker-skinned neonates (Fitzpatrick III–VI), while the blood gas analyser demonstrated superior diagnostic performance with a diagnostic odds ratio of 47.5.

What is the implication of the main findings?
Blood gas analysers represent a more reliable point-of-care alternative to serum bilirubin than transcutaneous bilirubinometry for neonatal hyperbilirubinaemia screening and hyperbilirubinaemia tracking, particularly valuable in time-critical or resource-limited clinical settings, where rapid, accurate results are essential.While transcutaneous bilirubinometry remains useful as a non-invasive screening tool, positive findings require confirmatory serum bilirubin testing, especially in post-phototherapy neonates and those with darker skin tones, to prevent misclassification and overtreatment.

Blood gas analysers represent a more reliable point-of-care alternative to serum bilirubin than transcutaneous bilirubinometry for neonatal hyperbilirubinaemia screening and hyperbilirubinaemia tracking, particularly valuable in time-critical or resource-limited clinical settings, where rapid, accurate results are essential.

While transcutaneous bilirubinometry remains useful as a non-invasive screening tool, positive findings require confirmatory serum bilirubin testing, especially in post-phototherapy neonates and those with darker skin tones, to prevent misclassification and overtreatment.

Background: 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. Objective: 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. Methods: 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. Results: 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. Conclusions: 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.