Abstract
In preparation for multivariate analysis, an exploratory study has been undertaken to investigate the relative position, separability, homogeneity and shape of three major disease groups, using data from a clinical chemical routine package. The data set consists of 46 hepatology patients, 50 nephrology patients and 46 cardiology patients, and the measured blood levels include 20 common clinical chemical routine assays. Missing value problems were avoided by deleting some of the variables and objects. A univariate analysis was used as the basis ofa rescaling of the data. Bivariate (pairwise) plots of some major assays each show limited separation. The set of three such plots of the three major principal components reveals more distinction between the groups than was offered by univariate analysis. Three-dimensional extensions of these techniques allow better insight than any of the two-dimensional plots, but these three-dimensional versions require more plots for complete interpretation. Non-linear mapping of the data is the best way of retaining the distances and a fairly good separation is achieved in the plot. The plot is less informative about shape and relative position of the classes. Representation of the data as pictures of faces does not offer additional information and visual clustering is worse than in any of the techniques mentioned. During the analysis many assumed properties of the data are confirmed and a good starting pointfor multivariate classification is attained. Easy visual detection of outliers is offered by all techniques. Unfortunately, valuable information is lost in this data set by deleting some incomplete variables.
Highlights
During the past decades the number of constituents that can be measured in body fluids has increased substantially
The aim of this study was to get an impression of the separability of HEART, LIVER and KIDNEY patients on basis of 20 routine assays, and of the presence of atypical cases in the data, and of the applicability and homogeneity of low dimensional class models
Views on the data are chosen that stress class characteristics rather than class differences
Summary
During the past decades the number of constituents that can be measured in body fluids has increased substantially. The physician could be advised to order only those assays that will give him the desired information, in other words, to order very selectively This requires a thorough knowledge of the value of the assays for each diagnosis. The introduction of protocols of diagnosis and treatment in medicine, supported by recent medical decision-making techniques, is an attempt to optimize the use of laboratory results by selection of an optimal subset of all assays for a specific problem. Advantages of this approach include reduction of overall costs and growing experience with a selection of assays, leading to assessment of their value
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