Measurements of neonatal bilirubin and albumin concentrations: a need for improvement and quality control

Abstract

Accurate and precise bilirubin and albumin measurements are essential for proper management of jaundiced neonates. Data hereon are lacking for Dutch laboratories. We aimed to determine variability of measurements of bilirubin and albumin concentrations typical for (preterm) neonates. Aqueous, human serum albumin-based samples with different concentrations of bilirubin (100, 200, 300, 400, and 500 μmol/L) and albumin (0, 10, 15, 20, 25, and 30 g/L) were sent to laboratories of all Dutch neonatal intensive care units (n = 10). Bilirubin and albumin recoveries of the specimens were measured using locally available routine analytical methods. The mean, standard deviation, and coefficients of variations (CV) were calculated per sample. Bilirubin concentrations were underestimated in the absence of albumin (maximal CV 26.0%). When the albumin concentration was 10 or 20 g/L, the bilirubin concentrations of the samples were overestimated (maximal CV 14.1% and 9.2%, respectively). Variability increased with higher weighed-in bilirubin concentrations. Measured albumin levels were ~10% lower than albumin levels of manufactured samples. Bilirubin concentration did not influence albumin measurements. The maximal CV was 6.8%. In conclusion, interlaboratory variability of bilirubin and albumin measurements is high. Recalibration and introduction of a specific quality assessment scheme for neonatal samples is recommended to ensure exchangeability of bilirubin and albumin measurements among laboratories and to control the observed large variability.

Fig. 1

a–c Variability of bilirubin measurements. Measured versus weighed-in bilirubin concentrations (17.1 μmol/L = 1 mg/dL bilirubin) in manufactured samples with albumin concentrations of 0, 10, and 20 g/L, respectively. The median of measured bilirubin concentration is marked by the horizontal line in the central box. The boxes are limited by the 25th and 75th percentile. The whiskers represent minimum and maximum measured bilirubin concentrations. Outliers (white circle) are depicted separately. Coefficients of variations (CV) are shown in Fig. 1b and c as well as the difference between the minimal and maximal measured bilirubin concentration, which is expressed as percentage of the weighed-in bilirubin concentration