Abstract
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Correlation And Precision of Serum Free Bilirubin Concentrations Determined by Single And Two Peroxidase Concentration Methods in Term or Late-Preterm Newborn Infants Using a FDA-Approved Analyzer
by Akihiro Miwa, Ichiro Morioka, Tomoyuki Yokota, Akio Shibata Kiyomi Matsuo, Kazumichi Fujioka, Tsubasa Koda, Satoru Morikawa, Hisahide Nishio, Naoki Yokoyama, Hajime Nakamura, Masafumi Matsuo, Hideto Yamada
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Background: Free bilirubin concentration (Bf) is an index for identifying newborns at risk for developing bilirubin-induced neurotoxicity. It has been suggested that Bf measured by a single peroxidase concentration (Bf-single) does not equal the equilibrium concentration of Bf, which is confirmed by Bf at two different peroxidase concentrations (Bf-two). However, the differences between Bf-single and Bf-two are unknown in the serum of term or late-preterm newborn infants. Furthermore, to apply Bf-single with savings on time and cost to the clinical setting, it is very important for us to clarify the differences between Bf-single and Bf-two.
Methods: Forty serum samples were obtained from 21 term or late-preterm newborns who were admitted at Kobe University Hospital. Using a peroxidase method, Bf-single was measured at one peroxidase concentration, and Bf-two was determined at two different peroxidase concentrations (the manufacturer’s recommended peroxidase concentration and half the manufacturer’s recommended peroxidase concentration). To clarify the relationship between Bf-single and peroxidase concentrations, Bf-single was measured at five different concentrations of peroxidase reagent. Intra-day and inter-day analyses were performed to assess the precision of Bf-single and Bf-two.
Results: 1/Bf-single increased as peroxidase concentration increased. Bf-single was significantly lower than Bf-two (Bf-single: 0.50 μg/dL [0.13 - 1.22 μg/dL] versus Bf-two: 0.59 μg/dL [0.15 - 1.76 μg/dL], p<0.001), but Bf-single was significantly correlated with Bf-two (r = 0.953, p<0.0001). Intra-day analysis showed that the CV was 9.7% for Bf-two and 3.3% for Bf-single, and the inter-day CV was 12.4% for Bf-two and 3.2% for Bf-single.
Conclusions: Although Bf-single and Bf-two are not identical, Bf-single is significantly correlated with Bf-two and it is more precise than Bf-two in term or late-preterm newborns.
DOI: Clin. Lab. 2012;58:507-514
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