One of PDHA’s tasks is to develop a differential diagnosis based on symptoms and other information. In this role it has been referred to as a symptom checker. In the perioperative period, anesthesiologists usually care for patients with established diagnoses. Many patients are familiar with their chronic conditions such as hypertension, diabetes, and cardiovascular disease and are receiving care. However, in the settings of preoperative clinic, perioperative surgical home, pain clinic, and intensive care unit, anesthesiologists may be called upon to diagnose and manage their patients.

Like the public, anesthesiologists can perform Google and other web search of the relevant information. Every day, over one billion of Google searches are health-related [1]. However, such a search may not integrate all the information that is known or can be elicited, and is usually not adequate for clinical management. PDHAs provide diagnosis decision support that is superior to internet searches. After the symptoms and other information are entered, the system asks a series of questions. Each question depends on the answer to the previous question. Usually only a few questions are asked. They consider the patient’s demographics and medical history. Some may also consider vital signs, input from physiological sensors, and laboratory values. The systems provide the differential diagnoses and management plans. They assist the physician in considering the full range of differential diagnoses and avoid missing a potential diagnosis. These systems have become practical tools for clinical diagnosis. They are most useful in pre-primary care setting. They pre-diagnose, triage, and can connect the patient to the appropriate medical facilities, providers, support services, and resources. They can assist call centers and emergency departments in triaging. They are most useful in diagnosing conditions that are not common.