Coagulation studies: achieving the right mix in a large laboratory network

Abstract

Basic coagulation tests, activated partial thromboplastin time (APTT), prothrombin time (PT) and the related international normalised ratio (INR), are performed frequently in hospital settings. From a laboratory perspective, unexpected abnormal results require further action; either informing the ordering clinician, or second line testing to determine the underlying cause. To streamline laboratory workflow, a new system of expert laboratory rules was implemented. The medical implications of this new laboratory system are evaluated here. The electronic ordering system was updated to mandate clinical information regarding the presence of an anticoagulant, or 'no anticoagulant'. When the PT or APTT were abnormal, and no anticoagulant was reported, second line testing was automatically performed. The second line tests performed were: mixing studies, fibrinogen and thrombin time. Any sample with a mixing study that did not completely correct, or fibrinogen <1.0 g/L, or INR >7.0, was flagged for clinical review by the laboratory haematology registrar. In a 17-month period there were 362,692 APTT, PT/INR and fibrinogen tests performed. Of these, 14,160 (3.9%) were abnormal with either no reported anticoagulant, or an unknown anticoagulant status. A total of 934 (0.3%) were referred for review by the haematology registrar. Three (<0.001%) cases received altered medical management as a result of the haematology registrar review. In hospital settings, most abnormal coagulation studies are anticipated by the ordering clinician. Unexpected abnormal coagulation results of clinical significance are rare. Automated second line coagulation testing and medical review improves laboratory workflow without compromising patient safety.