Is serum bilirubin concentration the only valid prognostic marker in primary biliary cirrhosis?



From the many prognostic models for primary biliary cirrhosis (PBC) patients based on Cox's regression analysis, the Mayo model has gained the most popularity and was successfully validated in some centers. The aim of our study was to validate the Mayo survival model for Polish PBC patients and, in case of its inapplicability, to select prognostic variables and to create time-fixed and time-dependent survival models for the patients. We used database information on patients from 6 medical centers in Poland, fulfilling clinical, serological, and/or pathological criteria of PBC. The Mayo model was validated using data from 116 PBC patients. The time-fixed and time-dependent models were created using data on clinical and biochemical variables used in the Mayo model from 162 and 208 patients, respectively. The Mayo model validation was performed graphically and by one-sample log-rank tests after dividing the study sample into 3 groups of high, medium, and low risk. The survival analysis was performed using Cox's proportional hazards regression method on clinical and biochemical variables used in the Mayo model. Treatment with ursodeoxycholic acid (UDCA) was included in the time-dependent analysis. Validation showed that the Mayo model overestimated death risk in Polish PBC patients. Of the variables used in the Mayo model, serum bilirubin concentration appeared to be the only variable of prognostic importance. The analysis shows that serum bilirubin concentration holds most of the prognostic information for our PBC patients irrespective of prior treatment with UDCA.