Aim To evaluate the impact of decision support on the proportion of troponin I (cTnI) tests and associated costs over the period 2000–7 for patients presenting with chest pain in an emergency department (ED) setting.

Methods A longitudinal study using linked data for patients presenting with chest pain from the ED and laboratory information systems of a metropolitan teaching hospital in Melbourne, Australia. The study period was divided into a pre-intervention period (2000–2), which contained no decision support; an initial post period (2003–4) after the introduction of a quality improvement initiative (utilising a paper-based guideline, education, audit and feedback) about cTnI test ordering and the incorporation of the guideline as a decision support feature of the computerised provider order entry system; followed by a post-modification period (2005–7) after the electronic decision support feature was modified to allow clinicians to bypass viewing the complete guideline.

Results There was a significant fall in the proportion of cTnI tests ordered per patient presentation across the three periods—pre (2000–2), post (2003–4) and post-modification (2005–7)—from 7.3% to 4.1% and 2.8%, respectively. Analysis of costs showed significant reductions in the mean costs for cTnI tests per patient presentation from $A9.28 to $A8.54 and $A8.18, respectively, which amounted to a modest saving of $A13 251 since the initiation of decision support in 2003.

Conclusions Decision support systems are often part of multifaceted implementations undertaken over time. They require continuous monitoring and modifications to ensure optimal performance.