As mentioned before, the practice of medicine is founded on the making the right medical decisions. It is no surprise then, that the major efforts of medical informaticians have been directed at the problem of the computerized medical decision making. Medical decision-support systems are computer applications that assist clinicians in making decisions about patient care. They are designed to aid health professionals by providing assessments or prompts that are specific to individuals and are selected from a knowledge base according to their characteristics. The systems also offer the potential to make an important contribution to the quality of health care by providing consumers with ‘just-in-time’ notification of best practice or possible adverse effects, and clinicians with access to relevant, evidence-based information at the point of care. There are various definitions for medical decision-support systems, including the following:

1. A medical decision-support system compares patient characteristics with a credible knowledge base and then guides a clinician by offering patient-specific and situation-specific advice. By incorporating evidence-based guidelines and a summary of the patient’s data, or knowledge base, the clinical decision making process is enhanced, thereby potentially improving the quality of care.
2. Clinical decision-support systems allow caregivers to identify the most appropriate treatment based on outcomes assessment and best practice development. These systems focus on improving clinical care by providing timely access to literature, test interpretations, determination of drug dosages, automated warnings and alerts, practice guidelines, and decision analysis.
3. Medical decision-support system is any software that directly aids clinical decision making in which characteristics of individual patients are matched to a computerized knowledge base for the purpose of generating patient-specific assessments or recommendations that are then presented to clinicians for consideration.
4. Clinical decision-support systems or expert systems are computer software systems that are designed to aid clinical decision-making. Computerized decision-support systems provide assessments of prompts specific to the patient and selected from a knowledge base on the basis of individual patient data. At its simplest form, this will include programs that suggest alternatives for treatment or diagnosis on the basis of a simple algorithm. More complex systems model the likelihood of future events and the effectiveness of proposed interventions based on individual patient data and ‘knowledge’ of risks and the effectiveness of interventions.

Whatever the definition is used, computerized decision-support systems are a rapidly advancing and unregulated field, with potential for harm as well as benefit if systems are poorly designed and inadequately evaluated.