The generalizability of the Mayo model for predicting survival in individual primary biliary cirrhosis patients without liver transplantation was tested and confirmed. The model was applied to a data base of patients from the New England Medical Center Hospitals (n = 141) and the Scott and White Clinic (n = 35) and found to predict their survival accurately. It was also shown to be accurate for Mayo primary biliary cirrhosis patients with very advanced disease (n = 301, those with less than a 33% chance of surviving 12 months. The analyses confirmed that the addition of histologic stage did not significantly improve the predictive power of the model (p > 0.10). We suggest that the Mayo model is a practical tool for clinical management and decision making. The need for a model t o predict survival for primary biliary cirrhosis (PBC) patients in the absence of effective treatment has long been recognized. In response to this need, three groups, Roll e t al. (1) at Yale, Christensen e t al. (2) in Europe and Dickson e t al.
(3) at the Mayo Clinic, have independently developed mathematical models to predict survival in any untransplanted PBC patient. All groups used the Cox proportional hazards multivariate regression procedure (4) but differed in the risk variables used for survival prediction. Nonetheless, the three models were highly correlated in their assessment of patient risk (3). T h e Mayo model has the advantage t h a t it is the only one t h a t does not require a liver biopsy or other invasive procedure.
The Mayo model is a promising clinical management tool, but additional tests of the model are needed. T h e model was developed and cross-validated on a Mayo patient data base (3). Its generalizability t o PBC patients in other medical centers must be assessed. T h e applica-