The Manitoba IBD Index: evidence for a new and simple indicator of IBD activity

A single-item indicator of disease activity over an extended period of time, the Manitoba Inflammatory Bowel Disease Index (MIBDI), is introduced and compared against several standard measures for assessing activity in patients with Crohn's disease (CD) and ulcerative colitis (UC).

Participants enrolled in the Manitoba IBD Cohort Study, a population-based longitudinal cohort study (N=353), were assessed semiannually by survey, clinical interview, and blood sample during a 2-year period. The MIBDI is based on patient self-reports of symptom persistence for the previous 6 months, using a 6-level response format.

The MIBDI had good sensitivity compared with the Harvey-Bradshaw Index (HB; 0.88), Powell-Tuck Index (PT; 0.84), and Inflammatory Bowel Disease Questionnaire (IBDQ; 0.89), which was maintained at two subsequent annual measurements. Test-retest reliability was also strong (Spearman's r=0.81). Discriminant function analyses identified common discriminating variables of active disease for CD and UC that included HB, PT, and IBDQ subscales of bowel and systemic symptoms, prolonged symptom severity (e.g., abdominal and joint pain, tiredness, diarrhea), and recent persistent pain related to IBD. Unique discriminators included weight problems (CD) and blood in stool (UC).

A single-item, patient-defined disease activity measure, the MIBDI, showed a high degree of sensitivity for classifying individuals with regard to disease status over time compared with the existing disease activity measures, and strong convergent validity with expected proxy measures of disease. These relationships remained consistent over time. Thus, the MIBDI shows promise as a valid, brief tool for measuring disease activity over an extended period.