Background and objectivesEndoscopy is the gold standard to assess disease severity in inflammatory bowel disease, although it is an invasive procedure. Clinical activity and biological markers have been routinely used to determine disease activity in a non-invasive manner. The aim of this study was to determine concordance between common biological markers (C reactive protein, orosomucoid, erythrocyte sedimentation rate, fibrinogen, platelets, leukocytes, neutrophils and haemoglobin) and clinical activity in inflammatory bowel disease. Patients and methodConsecutive patients with inflammatory bowel disease were included. Clinical activity was evaluated according to the Harvey-Bradshaw index in Crohn's disease and to the partial Mayo score in ulcerative colitis. Serum concentrations of the different biomarkers were analysed. Concordance between clinical activity and elevation of the serological biomarkers was determined using the kappa statistic. ResultsIn total, 350 patients were included (median age 46 years, Crohn's disease 59%). Eleven percent of patients had clinical activity. Crohn's disease patients had mild clinical activity in 44% of cases, moderate disease in 44% and only 12% of patients had severe clinical activity. In ulcerative colitis, patients had mild, moderate and severe clinical activity in 50, 42 and 8% of cases, respectively. None of the biomarkers included had an acceptable concordance with clinical activity (kappa statistic≤0.30). ConclusionsConcordance between serological biomarkers and clinical activity in inflammatory bowel disease is remarkably low.