Comparison of a disease activity index and patients' self-reported symptom severity in ulcerative colitis

Background: A self-report instrument to measure disease activity in ulcerative colitis was compared with a full-scale measure of clinical and endoscopic activity, the St. Mark's index. We also tested the effects of symptom reporting style on both instruments. Methods: Disease activity was measured in 94 patients with ulcerative colitis using the St. Mark's index and an instrument consisting of 7 self-reported symptoms. Reporting style was measured as health anxiety, measured with the Illness Behavior Questionnaire, and repressive coping, defined by scores on the Marlow-Crowne questionnaire and the State Anxiety Index. Results: The St. Mark's index and the self-report index were highly correlated (R-2 = 0.98 P < .001). Compared with the St. Mark's index, the self-report index categorized patients into inactive or active disease with a positive predictive value of 100% and negative predictive value of 100%. Reporting style was associated with differences in disease activity in both disease severity scales. Conclusions: A self-report measurement of ulcerative colitis disease activity is a valid alternative to complete clinical and endoscopic examination in subjects who do not have severe illness. Determination of disease severity in ulcerative colitis is vulnerable to individual biases in symptom reporting style, not only in self-report instruments, but also in an index that includes endoscopy and physical examination.