Survival following the development of ascites and/or peripheral oedema in primary biliary cirrhosis: a staged prognostic model.
OBJECTIVE
Current prognostic models in primary biliary cirrhosis (PBC) have low precision, partly due to the restricted inclusion criteria of some cohorts used for modelling but also because of the prolonged natural course of the disease. It is hypothesized that better precision could be achieved with a staged model, using ascites or peripheral oedema as a new starting-point for prediction.


METHODS
The study was based on an established database of 289 consecutive patients, followed between 1977 and 1998. Stepwise Cox regression was used to construct a staged model based on 143 patients who first developed ascites (n=111) or peripheral oedema (n=32) at entry or during subsequent follow-up. The model was compared with published models using graphical methods and receiver operating characteristics (ROCs).


RESULTS
Mean time from clinical diagnosis of ascites or peripheral oedema to death was 3.1 years. The following variables had independent prognostic significance: log10(bilirubin) (p<0.001), albumin (p<0.001), age (p<0.001) and history of encephalopathy (p<0.001). Goodness of fit showed that the survival probabilities predicted by the Ascites Stage Model fitted well with the observed data. The Ascites Stage Model (ROC 0.8324 (SE 0.0348)) was a better predictor of survival than the Mayo long-term model (ROC 0.7833 (SE 0.0397)), the Mayo Repeated Patient Visits Model (ROC 0.7779 (SE 0.0399)) and the Royal Free PBC Prognostic Model (ROC 0.7785 (SE 0.0396)).


CONCLUSIONS
The Ascites Stage Model gives a better survival estimate for PBC patients once they have developed ascites or peripheral oedema compared with the current models, and demonstrates an advantage of staged models in diseases with a prolonged natural history.
Chan
Chun-Wing
CW
Liver Transplantation and Hepatobiliary Medicine, Royal Free Hospital, London, and Medical Statistics Unit, London School of Hygiene and Tropical Medicine, UK.
Carpenter
James R
JR
Rigamonti
Cristina
C
Gunsar
Fulya
F
Burroughs
Andrew K
AK
D001201:Ascites / Q000209:etiology / Q000401:mortality*; D018450:Disease Progression; D004487:Edema / Q000209:etiology / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000150:complications* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012720:Severity of Illness Index; D015996:Survival Rate / Q000639:trends; D013997:Time Factors