Electronic test ordering, via the Electronic Medical Record (EMR), which incorporates computerised provider order entry (CPOE), is widely considered as a useful tool to support appropriate pathology test ordering. Diagnosis-related groups (DRGs) are clinically meaningful categories that allow comparisons in pathology utilisation by patient groups by controlling for many potentially confounding variables. This study used DRG data linked to pathology test data to examine changes in rates of test ordering across four years coinciding with the introduction of an EMR in six hospitals in New South Wales, Australia. This method generated a list of high pathology utilisation DRGs. We investigated patients with a Chest pain DRG to examine whether tests rates changed for specific test groups by hospital emergency department (ED) pre- and post-EMR. There was little change in testing rates between EDs or between time periods pre- and post-EMR. This is a valuable method for monitoring the impact of EMR and clinical decision support on test order rates.