Numerical Taxonomy and Discriminant Analysis Applied to Non-specific Colitis

Abstract

The present concept of non-specific colitis envisages two groups of patients designated as suffering from proctocolitis and colonic Crohn's disease but the diagnostic features of these two groups overlap and it may be impossible to classify individual patients. The subject is controversial and the technique of numerical taxonomy, which makes no prior assumption that a population is divisible into groups, has therefore been applied to the problem. A series of 109 consecutive patients with non-specific colitis has been studied using 107 clinical, radiological, and pathological attributes. The taxonomic analysis yielded one large cluster and several smaller clusters of patients. Comparison of these clusters with the clinical diagnosis showed that the large cluster contained mainly patients diagnosed as suffering from proctocolitis whereas patients diagnosed as suffering from Crohn's disease of the colon were distributed among the smaller clusters. These results suggest that the disorder now termed proctocolitis comprises a single, relatively uniform group of patients whereas that described as colonic Crohn's disease is more heterogeneous. The attributes which separated the main cluster from the other smaller clusters have been identified. When the taxonomic analysis was repeated using the smaller number of attributes a simpler grouping emerged, there being one large cluster as before but only two smaller clusters. The large cluster again contained mainly patients diagnosed clinically as suffering from proctocolitis and the two smaller clusters mainly those diagnosed clinically as suffering from Crohn's disease. Analysis of the attributes which separated the two smaller clusters showed that one contained largely patients with ano-rectal Crohn's disease and the other largely patients with Crohn's disease involving the proximal large bowel. Stepwise discriminant analysis has shown that separation between the large cluster and the other smaller clusters could be achieved in this series almost entirely by the use of five of the 107 attributes recorded. These attributes were the histological finding of mucus depletion, the physical findings of an abnormal anal canal and a normal sigmoidoscopic appearance of the rectal mucosa, the radiological appearance of granularity of the mucosal line in a double contrast barium examination of the affected bowel and the symptom of tenesmus.