The slides of 46 biopsies (35 wedge biopsies and 11 percutaneous biopsies) and one from a postmortem examination, all from patients hospitalized for neonatal cholestasis at the Pediatrics Service of Hospital de Clínicas de Porto Alegre, were prospectively studied from December 1987 to January 1991. At least 4 of 5 different stains were used, and 46 histopathological variables from the protocol introduced by Zerbini (19) were assessed, and the findings were scored on a 0 to 4 scale according to the degree of severity (0 - absent; 1 - mild; 2 - moderate-mild; 3 - moderate-severe; 4 - severe). The stains used were hematoxylin-eosin, trichromic green, picrosirius, PAS and reticulin. Sections of percutaneous biopsies which had less than 3 portal spaces were excluded from the study. Slides were scored by a pathologist who was unaware of the final diagnosis of each case. The cases were divided into 2 groups according to the diagnostic histopathologic impression: extrahepatic biliary pattern (EHBP) or parenchymatous pattern (PP). Biliary permeability was defined in each case by scintigraphy of the bile ducts and, in the absence of excretion of the radiotracer to the duodenum by this method, by operative cholangiography.
Data analysis
Discriminant analysis was used as a statistical method for the study of the histopathological variables in order to determine possible significant differences between the EHC and IHC groups based on information of independent variables, and which independent variables would contribute to the differentiation between the 2 groups. In order to use this technique, the variables were originally treated as being continuous. Due to the high number of variables being studied, a previous selection of these variables by means of the F test was carried out, and only those which were found to be significant by this test were subjected to the discriminant analysis, with the level of significance set at 5%. After selection by the F test, 22 variables of 47 patients were assessed by the discriminant analysis test. In this test the total sample (N = 47) was divided into two groups: the first group (N = 30) was used to obtain the discriminant function, and the second (N = 17) for the discriminant function test (accuracy). A "stepwise" computational model was used to assess the independent variables in each step, including or excluding them from the model according to their discriminatory power. Thus, it was possible to establish which variables were most significant for the distinction between the EHC and IHC groups.
The chi-square method with Yates correction was used to relate the age of the patients at the time of liver biopsy to the discriminant hepatic histopathological variables between IHC and EHC selected by the discriminant function test.
The significance level adopted for the statistical tests was 0.05 (two tailed).
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