Goals and Background:The objective is to develop a patient-based Harvey Bradshaw Index (P-HBI) of Crohn's Disease (CD) activity and to compare it with the clinician-based HBI of CD activity in CD outpatients.Study: Consecutive patients with CD randomly completed the P-HBI either before or after the consultation. The gastroenterologist assessed patient's CD activity on the same day. Overall agreement between HBI and P-HBI was calculated with Spearman's r and Mann-Whitney U test. Agreement regarding active disease versus remission and agreement at item level was calculated by percent agreement and Cohen's k.Results: One hundred eighty-one (response rate 88.3%) CD patients participated. P-HBI and HBI showed a large correlation (r s = 0.82). The medians (interquartile range) of the total HBI (2; 0 to 4) and P-HBI (4; 1 to 7) were statistically significantly different (z = À 8.411; P < 0.001). Fortunately, in 82.6% of the cases this difference between clinicians and patients was not clinically significant (< 3.2). The percentage agreement between clinician and patient, judging CD as active or as in remission, was 77%, r s = 0.56, k = 0.52, indicating a moderate agreement. P-HBI and HBI on frequent extraintestinal manifestations in CD varied from less than chance (k = À 0.02) to a perfect agreement (k = 1). Patients tended to report more symptoms while completing the patientbased questionnaire compared to what they reported to the clinician during consultation. Conclusions:The P-HBI is the first step in developing a potential promising tool given its adequate agreement with the original HBI and its feasibility, especially in patients with low scores. Future research is necessary to develop a validated patient-based version studied in several patient populations.