Clinical Chemistry, Vol 16, 239-246, Copyright © 1970 by the American Association for Clinical Chemistry

Comparison of the Weber-Schalm Method with the Ducci-Watson Modification of the Malloy-Evelyn Method for Serum Bilirubin Determination

¹ University of Minnesota Medical Unit, Northwestern Hospital, Minneapolis, Minn. 55407.

Unconjugated bilirubin, conjugated bilirubin, and mixtures of various proportions of each were dissolved in depigmented human serum. These, together with normal and pathologic native human sera, were analyzed for conjugated, unconjugated, and total bilirubin by the Weber-Schalm method. Results were compared with the determination of "prompt direct reacting bilirubin" and of total bilirubin by the Ducci-Watson modification of the Malloy-Evelyn method. Comparisons show that the Weber-Schalm method more accurately measures conjugated bilirubin concentrations in serum in which the bilirubin is mostly conjugated, but that it gives falsely high values for unconjugated bilirubin in serum in which more of the bilirubin is in the unconjugated form. The two methods gave statistically identical total bilirubin values for the native serum tested. A method is described for correcting the unduly low values for prompt, direct reacting bilirubin in terms of percentage of conjugated bilirubin.