ORIGINAL ARTICLE

Neonatal bilirubin production-conjugation imbalance: effect of glucose-6-phosphate dehydrogenase deficiency and borderline prematurity

M Kaplan^1,2, M Muraca^4,*, H J Vreman⁶, C Hammerman^1,3, M T Vilei⁴, F F Rubaltelli⁵ and D K Stevenson⁶

¹ Department of Neonatology, Shaare Zedek Medical Center, Jerusalem, Israel
² Faculty of Medicine, Hebrew University, Jerusalem, Israel
³ Faculty of Health Sciences, Ben Gurion University of the Negev, Be’er Sheva, Israel
⁴ Department of Internal Medicine, University of Padua, Florence, Italy
⁵ Department of Neonatology, University of Florence, Florence, Italy
⁶ Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University Medical Center, Stanford, CA, USA

Correspondence to:
Correspondence to:
Dr Kaplan
Department of Neonatology, Shaare Zedek Medical Center, PO Box 3235, Jerusalem 91031, Israel; kaplan{at}cc.huji.ac.il

Objective: To evaluate relations between production and conjugation of bilirubin in the pathophysiology of jaundice in glucose-6-phosophate dehydrogenase (G6PD) deficient neonates.

Methods: Term and borderline premature (35–37 weeks gestational age), healthy, male, G6PD deficient neonates were studied close to the beginning of the 3rd day. Blood carboxyhaemogobin corrected for inspired CO (COHbc; an index of bilirubin production) and serum total conjugated bilirubin (TCB; a reflection of bilirubin conjugation) were measured in simultaneously drawn blood samples by gas chromatography and reverse phase high performance liquid chromatography respectively. A bilirubin production-conjugation index comprising COHbc/TCB was determined; a high index reflects imbalance between the bilirubin production and conjugation processes. COHbc and TCB individually and the production-conjugation index were studied in relation to serum total bilirubin (STB) concentration.

Results: Fifty one G6PD deficient neonates were sampled at 51 (8) hours. COHbc values did not correlate with STB (r = 0.22, p = 0.15). TCB did correlate inversely with STB (r = –0.42, p = 0.004), and there was a positive correlation between the production-conjugation index and STB (r = 0.45, p = 0.002). The production-conjugation index (median (interquartile range)) was higher in the premature (n = 8) than term neonates (2.31 (2.12–3.08) v 1.05 (0.53–1.81), p = 0.003). This difference was the result of changes in TCB.

Conclusions: The data show that jaundice in G6PD deficient neonates is the result of an imbalance between production and conjugation of bilirubin with a tendency for inefficient bilirubin conjugation over increased haemolysis in its pathogenesis. Borderline premature infants are at especial risk of bilirubin production-conjugation imbalance.

Abbreviations: COHb, carboxyhaemoglobin; COHbc, COHb corrected for inspired (room air) CO; G6PD, glucose-6-phosphate dehydrogenase; HPLC, high performance liquid chromatography; STB, serum total bilirubin; TCB, total conjugated bilirubin

Keywords: bilirubin; glucose-6-phosphate dehydrogenase; bilirubin conjugation; borderline prematurity; haemolysis

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