The role of neopterin in assessing disease activity in Crohn's disease: classification and regression trees

Neopterin, a product of human monocytes/macrophages stimulated by gamma-interferon, was previously found to be correlated with clinical activity of Crohn's disease. The present investigation attempted to identify more precisely the role of neopterin for assessment of clinical activity in a multivariate setting. A broad panel of clinical and laboratory variables was obtained on 76 patients. Neopterin was determined in urine by high performance liquid chromatography. Using a 4-point clinical activity score as dependent variable, multivariate linear discriminant analyses were performed in order to identify subsets of statistically independent laboratory activity indices. Neopterin was shown to be an independent indicator for clinical activity. The significant variables were then tested together with the eight constituent variables of the Crohn's Disease Activity Index. The resulting model, which consisted of the three laboratory variables--erythrocyte sedimentation rate, serum protein and neopterin, together with pain score--was further subjected to two multivariate techniques for comparison: polychotomous logistic regression analysis and the technique of classification and regression trees. By all methods, neopterin was included into the multivariate models, confirming that its determination aids in the assessment of clinical activity in Crohn's disease.