Correlation between patient-determined inflammatory bowel disease severity and the inflammatory bowel disease severity index.

AIM: The inflammatory bowel disease severity index (IBD-DSI) aims to describe inflammatory bowel disease (IBD) severity over the duration of disease. We aimed to correlate the IBD-DSI with a patient-completed disease severity score (PCDSS). We also aimed to investigate whether individual factors such as psychological measures or clinical characteristics moderate this correlation.

METHODS

This multicentre trial involved gastroenterologists completing the IBD-DSI and Harvey-Bradshaw Index or Simple Clinical Colitis Activity Index for each participant while patients completed a self-reported IBD severity score and psychological questionnaires. The excess severity score (ESS) was calculated by subtracting the IBD-DSI from the PCDSS.

RESULTS

One hundred and sixty-four patients with IBD participated (98.2% response rate; average age 41.2 years; 105 [62.9%] female; 100 [59.9%] Crohn's disease) and 164 IBD-DSI were completed. The IBD-DSI and PCDSS were positively correlated (r=0.44, r2=0.19, p<0.001) although the mean ESS was 29.0 (23.2). The relationship between the scales is reflected in the equation: PCDSS=39.53+0.59*IBD-DSI. There were larger discrepancies at the lower end of IBD-DSI. After controlling for IBD-DSI, previous colectomy (p=0.03), any IBD or bowel-related surgery (p=0.01) and ulcerative colitis extent of disease (p=0.049) were associated with ESS while 5-aminosalicylic acid use (p=0.01) was negatively associated with ESS.

CONCLUSIONS

IBD-DSI and PCDSS are significantly positively associated with each other and with larger discrepancies at the lower end of the IBD-DSI. Possible contributing factors to the discrepancy are floor effects, regression to the mean and patients putting different implicit weights on particular factors than the IBD-DSI does.