Evolutive pattern in Crohn's disease: a simplified index using clinical parameters predicts obstructive behaviour

Two clearly differentiated evolutive patterns of Crohn's disease, obstructive and fistulizing, exist, but the early clinical parameters which can predict the evolution are unknown. To evaluate whether clinical variables, present at the time of diagnosis, may help in predicting a subsequent evolutive behaviour. Ninety out of 140 evaluable patients were included. After a median of 50.2 months since diagnosis, 64 patients (71%) followed an obstructive pattern while 26 patients (28.9%) had a fistulizing form. Clinical variables were analysed as predictors of outcome. Logistic regression was carried out in order to obtain a mathematical model that would predict the evolution. The individual ability of the mathematical model to predict evolution was assessed using relative receiver operating characteristic (ROC) curves. The variables which were retained in the model were duration of disease before diagnosis (DD), onset of symptoms (OS), presence of anal disease (AD) and the presence of abdominal mass (AM). The equation z = -9.49 + 2.2643 (AD) - 0.0066 (DD) + 2.5282 (AM) + 1.3433 (OS) was obtained. The probability of evolution towards an obstructive form was P = 1/(1 + e(-Z)). This model can predict 96.88% of obstructive forms but only 53.85% of fistulizing forms. The mathematical point section (ROC curve) corresponds to a probability of 45.2%. Considering an obstructive pattern when the probabilities are above this point, the sensitivity is 98% and the specificity is 50%. The prediction of an obstructive pattern is feasible using simple clinical variables. The mathematical model obtained is useful for predicting this but not the fistulizing pattern.