Selection and Assessment of Laboratory Tests for the Evaluation of Liver Functional Impairment

Evaluation of univariate ranges with a multivariate standard

In medical decision making generally many test results are produced. Several authors have discussed the problems involved and concluded that a multivariate approach often has to be preferred. Because until now such an approach has not often been used in practice and qualitative arguments for a multivariate approach are seldom supported by quantitative results, in this paper the use of univariate reference ranges is evaluated with a multivariate range as the standard, taking into account correlation coefficients. Probabilities of false positive and false negative results and predictive values are computed and displayed for decision rules based on two separate test results with an elliptic region as the gold standard. The conclusion is that the quality of the univariate approach is dependent on the correlation coefficient and on the choice of the decision rule. In the most important cases, however, it falls short compared with a multivariate approach. For example, the probability that a univariate positive result is false is around 50% for all values of the correlation coefficient, which is unacceptably high.

Evaluation of the diagnostic value of serum bile acid in the detection and functional assessment of liver diseases

The diagnostic usefulness of fasting total serum bile acids (SBA/F) in the detection of liver diseases and assessment of different aspects of hepatic function alteration was evaluated in 61 healthy subjects and 186 patients with liver disease. The value of SBA/F was compared with other routine tests. In 49 healthy subjects and 92 patients, serum bile acids were also measured after the im administration of Ceruletide as a cholecystokinetic agent (SBA/C). The diagnostic efficacy for the detection of disease states was better with aspartate-aminotransferase (EC 2.6.1.1) and alanine-aminotransferase (EC 2.6.1.2) than with SBA/F. When SBA/C was also determined the diagnostic efficacy was not substantially better than the SBA/F test. In the assessment of hepatocellular necrosis SBA/F showed a higher rate of misclassification errors compared to alanine-aminotransferase (mean error 45% vs 17%), whereas SBA/F gave similar results with direct bilirubin and pseudocholinesterase (EC 3.1.1.8) in the evaluation of cholestasis (mean error 40% vs 41%) and impaired biosynthesis (mean error 39% vs 40%), respectively. Serum bile acid determination did not show any significant diagnostic advantage with respect to the other routine liver tests.