Patanwala et al developed a score for predicting the probability of esophageal varices in patients with primary biliary cirrhosis (PBC). The authors are from Newcastle University, Freeman Hospital, Royal Liverpool University Hospital, Cambridge University Hospital, Toronto Western Hospital and the University of Birmingham.
Patient selection: primary biliary cirrhosis
Parameters:
(1) serum alkaline phosphatase in IU/L
(2) serum albumin in g/L
(3) platelet count in 10^9/L
(4) splenomegaly on endoscopic ultrasonography, > 12 cm (0 if absent, 1 if present).
X =
= (0.001 * (alkaline phosphatase)) - (0.178 * (albumin)) - (0.015 * (platelet factor)) + 9.186
Y =
= (2.013 * (points for splenomegaly)) - (0.138 * (albumin)) - (0.012 * (platelet factor)) + 6.385
probability of varices =
= 1 / (1 + EXP((-1) * (X or Y)))
where:
• The reference range for serum alkaline phosphatase was 30 to 130 IU/L.
• There is an online version of the calculator at www.uk-pbc.com/resources/uk-pbc-varices-prediction-tool.html.
• The online version includes a correction for the serum alkaline phosphatase to compensate for variation in the normal reference range. There does not appear to be a compensation for other methodologic variation.
Performance:
• The area under the ROC curve was 0.86.