[A probabilistic approach to the natural course of liver cirrhosis: a model of interactive simulation]

We propose a computerized mathematical model of the natural history of patients with liver cirrhosis in order to investigate the relationships between the various events that characterize the clinical course of the disease. By means of a rigorously probabilistic approach, the stimulation exposes each hypothetical patient to a series of risks of significant clinical events; whether or not these events occur is determined by preestablished probabilities. Analysis of the effects of arbitrary modifications of these theoretical risks provides useful information on the prospective relevance of the clinical events examined. For example, we compared the simulated follow-up of a population of control cirrhotic subjects with follow-ups of patient groups in whom different degrees of reduction of the risk for gastroesophageal bleeding were postulated on the basis of hypothetical primary or secondary prophylaxis. Our data confirm that the size of the investigated population strongly influences the threshold level of the bleeding-risk reduction able to determine a significant improvement in overall survival. In fact, in large populations (a 6 year follow-up of 3000 cirrhotic subjects), the threshold level was 25% (primary risk) and 45% (secondary risk) with respect to control subjects, while in more limited populations (300 subjects) even a 100% risk-reduction does not seem sufficient to bring about significant improvement in overall survival. Our data may help to explain the different results of controlled trials found in the literature; in fact, only the conclusions arrived at through meta-analysis procedures in large populations have been confirmed.(ABSTRACT TRUNCATED AT 250 WORDS)