Weaknesses in the classification criteria for antithrombotic-related major bleeding events

We asked two physicians to review the medical records (electronic and paper) of 100 patients on antithrombotics.The physicians used published classification criteria to identify all of the bleeding events that the patients experienced.The goal of the review was to investigate whether the physicians would identify the same antithrombotic related major bleeding events (ARMBEs) for each patient.The correct identification and classification of multiple bleeding events is a prerequisite for studies of antithrombotic treatment practices during hospitalization that predispose patients to ARMBEs. In addition, we were interested in the reasons for disagreement between the physicians, so that we could find ways of improving their agreement.The reviewers identified 299 bleeding events for the 100 patients.They disagreed on whether 29 of the events represented an ARMBE occurring during hospitalization. With a kappa statistic of 0.49 (95% confidence interval, 0.31 to 0.66) the agreement was moderate. The reviewers most often disagreed either because they misinterpreted the data (12 events) or because the classification criteria for ARMBEs were not explicit enough (9 events). Disagreement took two main forms: either the reviewers disagreed on ARMBEs by not identifying the same bleeds (11 events) or by not applying the severity criteria appropriately (7 events). Because the main type of disagreement was not identifying the same bleeds, a study investigating the antithrombotic treatment practices that predispose patients to ARMBEs would be threatened.We therefore proposed supplementing the existing classification criteria with additional rules to avoid ambiguities in patients with multiple events.