Medical decision-support systems can deliver many benefits for the health care of consumers. By assisting consumers and health care professionals in making important decisions, clinical decision-support systems can contribute to improve safety and quality of health care, and ultimately, to improve patient outcomes. They can contribute to enhanced quality of care through increased application of clinical pathways and guidelines, and greater use of up-to-date evidence to support evidence-based medicine. There is also potential for clinical decision-support systems to support greater efficiency in health care delivery through faster order processing, fewer duplicated tests, safer prescribing to reduce adverse events and changed patterns of prescribing towards less costly generic brands. Generally, potential benefits from medical decision-support systems are classified into three broad categories:

1. The Evidence for Improved Patient Safety: Clinical decision-support systems can improve patient safety through reduced medication errors and adverse events and improved medication and test ordering. The automation of clinical orders improves standardization and reduces problems such as the legibility of orders. Thus Physician Order Entry (POE) is particularly useful in improving accuracy of drug ordering, the stage most likely to have a significant impact upon reducing these type of adverse events. The most convincing evidence that Electronic Prescription Decision-Support Systems (E-PDS) can significantly reduce medication errors and adverse drug events derives from two seminal studies undertaken at the Brigham and Women’s Hospital in Boston, Massachusetts. The first study used a pre/post E-PDS system implementation study design and demonstrated a 55% reduction in potential adverse drug events following system implementation. The rate of adverse drug events fell from 10.7/1000 patient days to 4.9 per 1000 patient days. Within this category a reduction of 84% in the rate of non-intercepted potential adverse drug events from 6.0 to 1.0 per 1000 patient days was found. The second study used a time series design and examined changes in medication errors over three time periods (5 months, 2.5 years and 4 years) and found decreases in several categories of medication errors. Overall, there was an 81% decrease in medication errors pre and post E-PDS system implementation, and an 86% reduction in potential adverse drug events from time of pre to 4 years post-implementation. Medical decision-support systems have the potential to not only reduce medications errors but also to change medication prescribing patterns resulting in more cost-effective drug selection. Teich reported the impact of computerized order entry on the drug ordering behavior of clinicians over a 3 year period. They examined four specific drug decision-support interventions embedded in the E-PDS system. Data relating to each of the four drug ordering practices prior to the implementation of the order entry system were collected and then compared with drug ordering patterns immediately and at 1, 2 and 3 years post-system implementation. For all drug ordering interventions an immediate positive impact was found with greater compliance with the recommended drug orders. Compliance with the generic drug choice changed from around 14% pre-implementation to over 80% two months post system implementation and to 97% compliance at 1 and 2 year follow-up. The proportion of drug orders which exceeded the recommended maximum dose dropped from 2% in the pre-implementation period to less than 0.3% two years post-implementation. Overall, there is now a body of studies which provides some good evidence of the effectiveness of clinical decision-support systems, specifically computerized medication order entry systems, to increase the safety of patients by reducing errors, adverse events and by increasing the proportion of appropriate and safe prescribing decisions.
2. The Evidence for Improved Quality of Care and Patient Outcomes: Medical decision-support systems are useful by increasing clinicians’ available time for direct patient care, increasing application of clinical pathways and guidelines, facilitating the use of up-to-date medical evidence, improved clinical documentation and patient satisfaction. Hunt’s systematic review of medical decision-support systems reported that of 19 systems (18 in primary care) aimed at providing preventive care reminders, 14 (74%) reported benefits to the processes of care, thus concluding that preventive care reminder systems are a reasonably effective intervention in an ambulatory setting. One potential benefit of the implementation of order entry systems is that they increase the efficiency of administrative tasks and thereby allow clinicians to spend more time in direct patient care. This indicator has been measured using work sampling methods. Shu undertook a study of the impact of POE on time spent ordering, and available time for other tasks at Massachusetts General Hospital in the United States. He applied a modified version of work sampling using a random reminder method. 43 physicians pre-implementation and 29 post-implementation carried pagers which were set to go off 1.8 times per hour. On each of these occasions physicians recorded their current activities in a logbook using predefined codes. Post-implementation interns spent 3% more of their time with patients (from 13% to 16%), 6% more of their time alone (32% versus 38%) and less time with other physicians (47% versus 41%). Medical decision-support systems have also been shown to be able to significantly improve the quality of medical care by helping clinicians comply with ever-changing management guidelines and care standards. There is evidence that medical decision-support systems can increase compliance with clinical pathways and guidelines and reduce rates of inappropriate diagnostic tests. They can support increased use of evidence by clinicians in direct patient care, resulting in better patient outcomes.
3. The Evidence for Improved Efficiency of Health Care Delivery: Medical decision-support systems reduce costs through faster order processing, reductions in test duplication, decreased adverse events, and changed patterns of drug prescribing favouring cheaper but equally effective generic brands. In a randomized controlled trial, Tierney demonstrated that patients treated by physicians who used a POE containing decision-support information, which included costs of specific drugs and diagnostic tests, had less expensive hospital stays than did patients treated by clinicians without access to the POE system. Extrapolation of the cost savings due to reduced costs per admission were in the order of $3 million for the teaching hospital. Another study of the time taken for clinicians in an acute care setting to view test results available online found that 45% of urgent accident and emergency department biochemistry test results and 29% of ward requests were never accessed via ward terminals. Around one quarter of results were accessed within an hour of becoming available. A further 16% were accessed between 1-3 hours. In 3% of the accident and emergency department results which were never accessed, retrospective review showed that the findings may have led to an immediate change in clinical management.

Overall, the available evidence of the ability of medical decision-support systems to deliver improvements in the quality, safety and efficiency of health is promising. However, there remains a need to continue to monitor and evaluate the implementation of such systems to build the evidence base and ensure that their full potential is realized.