The Direct Spectrophotometric Method Is Reliable for Initial Assessment of Total Bilirubin in Neonatal Venous Plasma

Abstract

Objective: To determine the consistency of bilirubin values between the direct spectrophotometric (DS) and colorimetric diazo (diazo) methods in neonatal venous plasma specimens.

Methods: We measured the total bilirubin via the DS and diazo methods in 255 neonatal venous plasma specimens and compared the overall and subgroup results.

Results: Slight underestimation of total bilirubin values in most specimens using the DS method was observed, with higher mean biases found in higher concentrations. Significantly high positive correlations were found in all groups in which most of the different values were within the limits of agreement. DS cutoff of > 12 mg/dL showed 100% for all predictive indices in comparison with the diazo cutoff > 15 mg/dL.

Conclusions: Measurement of total bilirubin in neonatal venous plasma using the DS method had favorable agreement and high correlation with the diazo method. Therefore, the direct spectrophotometric method can be used as a reliable screening method.

Keywords: bilirubin; colorimetric diazo method; direct spectrophotometric method; method comparison; neonate; venous plasma.