1. A method for classifying whether a sample from an individual is associated with inflammatory bowel disease (IBD), said method comprising: (a) determining the presence or level of at least one marker selected from the group consisting of an anti-neutrophil antibody, anti- Saccharomyces cerevisiae antibody, antimicrobial antibody, C-reactive protein (CRP), and combinations thereof in said sample; and (b) classifying said sample as an IBD sample or non-IBD sample using a statistical algorithm based upon the presence or level of said at least one marker.