Accurate direct spectrophotometric bilirubin measurement combined with blood gas analysis

Background: A new total bilirubin (B-T) method, based on multiple wavelength absorbance measurements, and an algorithm to calculate concentration, were evaluated for accuracy in specimens containing variable amounts of unconjugated bilirubin (B-U), conjugated bilirubin (B-C) and delta (protein-bound) bilirubin (B-D). Methods: Quantitation of B-U, B-C, and BT (with calculation of B-D) using a Vitros 250 analyzer served as the comparison method. Results: Analysis of neonatal specimens using a preliminary algorithm yielded good overall agreement with the Vitros BT method, but there was considerable variation in the agreement for individual specimens, When specimens from adults selected to yield a range of B-C and B-D levels were analyzed, the preliminary algorithm underestimated B-T. Refinement of the method in the form of a finalized algorithm resulted in elimination of the negative bias seen with specimens with high B-D and B-C levels, and better agreement for individual neonatal specimens. Conclusions: This now method overcomes the limitations observed in earlier spectrophotometric methods, and provides accurate results in specimens containing a range of bilirubin forms. (C) 2002 Elsevier Science B.V All rights reserved.