Endoscopy 2010; 42(9): 742-747
DOI: 10.1055/s-0030-1255527
Original article

© Georg Thieme Verlag KG Stuttgart · New York

Validation of a cholangiographic prognostic model in primary sclerosing cholangitis

C.  Y.  Ponsioen1 , J.  B.  Reitsma2 , K.  M.  Boberg3 , L.  Aabakken3 , E.  A.  J. Rauws1 , E.  Schrumpf3
  • 1Department of Gastroenterology and Hepatology, Academic Medical Center, Amsterdam, The Netherlands
  • 2Department of Clinical Epidemiology, Biostatistics, and Bioinformatics, Academic Medical Center, Amsterdam, The Netherlands
  • 3Medical Department, Rikshospitalet, University of Oslo, Oslo, Norway
Weitere Informationen

Publikationsverlauf

submitted 5 November 2009

accepted after revision 28 April 2010

Publikationsdatum:
09. Juli 2010 (online)

Background and study aims: We previously developed a prognostic model for primary sclerosing cholangitis (PSC), which was primarily based on a cholangiographic classification of the intra- and extrahepatic biliary tree lesions. The aim of the present study was to validate the performance of this model in an external cohort.

Patients and methods: The validation dataset consisted of patients with PSC from a single referral center in Oslo, Norway. The patients’ cholangiograms were scored according to the Amsterdam classification. We then examined whether adjusting the value of the original coefficients of the predictors or adding new predictors would improve the fit of the original model in the validation cohort. In addition, we evaluated calibration (closeness between observed and expected survival) and discrimination using the concordance index.

Results: A total of 111 patients (mean age 35 ± 13 years; 76 % male) were included in the validation study. Baseline clinical characteristics were comparable between the two cohorts. None of the coefficients that were re-estimated in the validation cohort differed significantly from the values of the original model. Observed and expected survival curves were in close agreement across different risk groups. Discrimination of the original model was preserved in the validation cohort: the concordance index was the same in both cohorts.

Conclusions: The prognostic model showed adequate performance in an independent series of patients. Therefore, we updated the model using the data from both cohorts to provide more robust estimates of transplant-free survival for individual patients. A nomogram was constructed, which can be used to predict medium- and long-term prognosis in individual patients with PSC.

References

  • 1 Broome U, Olsson R, Loof L. et al . Natural history and prognostic factors in 305 Swedish patients with primary sclerosing cholangitis.  Gut. 1996;  38 610-615
  • 2 Ponsioen C Y, Vrouenraets S M, Prawirodirdjo W. et al . Natural history of primary sclerosing cholangitis and prognostic value of cholangiography in a Dutch population.  Gut. 2002;  51 562-566
  • 3 Rajaram R, Ponsioen C Y, Majoie C B. et al . Evaluation of a modified cholangiographic classification system for primary sclerosing cholangitis.  Abdom Imaging. 2001;  26 43-47
  • 4 Ponsioen C I, Tytgat G N. Primary sclerosing cholangitis: a clinical review.  Am J Gastroenterol. 1998;  93 515-523
  • 5 Schemper M, Smith T L. A note on quantifying follow-up in studies of failure time.  Control Clin Trials. 1996;  17 343-346
  • 6 Clark T G, Altman D G, de Stavola B L. Quantification of the completeness of follow-up.  Lancet. 2002;  359 1309-1310
  • 7 Craig D A, MacCarty R L, Wiesner R H. et al . Primary sclerosing cholangitis: value of cholangiography in determining the prognosis.  AJR Am J Roentgenol. 1991;  157 959-964
  • 8 Olsson R G, Asztely M S. Prognostic value of cholangiography in primary sclerosing cholangitis.  Eur J Gastroenterol Hepatol. 1995;  7 251-254
  • 9 Tischendorf J J, Hecker H, Kruger M. et al . Characterization, outcome, and prognosis in 273 patients with primary sclerosing cholangitis: a single center study.  Am J Gastroenterol. 2007;  102 107-114
  • 10 van den Hazel S J, Wolfhagen E H, van Buuren H R. et al . Prospective risk assessment of endoscopic retrograde cholangiography in patients with primary sclerosing cholangitis. Dutch PSC Study Group.  Endoscopy. 2000;  32 779-782
  • 11 Gluck M, Cantone N R, Brandabur J J. et al . A twenty-year experience with endoscopic therapy for symptomatic primary sclerosing cholangitis.  J Clin Gastroenterol. 2008;  42 1032-1039
  • 12 Justice A C, Covinsky K E, Berlin J A. Assessing the generalisability of prognostic information.  Ann Intern Med. 1999;  130 515-524
  • 13 Altman D G, Royston P. What do we mean by validating a prognostic model?.  Stat Med. 2000;  19 453-473
  • 14 Vergouwe Y, Steyerberg E W, Eijkemans M J, Habbema J D. Substantial effective sample sizes were required for external validation studies of predictive logistic regression models.  J Clin Epidemiol. 2005;  58 475-483
  • 15 Ponsioen C Y, Vrouenraets S M, van Milligen de Wit A W. et al . Value of brush cytology for dominant strictures in primary sclerosing cholangitis.  Endoscopy. 1999;  31 305-309
  • 16 Boberg K M, Jebsen P, Clausen O P. et al . Diagnostic benefit of biliary brush cytology in cholangiocarcinoma in primary sclerosing cholangitis.  J Hepatol. 2006;  45 568-574

C. Y. PonsioenMD 

Department of Gastroenterology and Hepatology
Academic Medical Center

P.O. Box 22700
1100 DE Amsterdam
The Netherlands

Fax: +31-20-6917033

eMail: c.y.ponsioen@amc.uva.nl