Past experience and gut instincts also play a role, and every clinician has his or her own methodology. Even the context of where the patient is seen may impact the assessment: a patient who is treated in the ER will receive less personalized care than someone seen by a specialist for the same complaint. Are Diagnostic Decision Support Systems (DDSS) the solution? They can make medical treatment more standardized, by using data-driven analysis based upon a wealth of experience much greater than one clinician can possess. However, not all DDSS systems may be equally effective. According to Bravata (et al. 2004): "Systems specifically designed to support the diagnosis of bioterrorism-relevant diseases or syndrome" were deemed "critically deficient," and as "false-positive and false-negative rates are unknown for most systems, decision making on the basis of these systems is seriously compromised." Not all DDSS systems are created equal, especially systems designed to give advice in extraordinary circumstances: the information sources within the DDSS database may be more limited.

For any illness, being too focused on common probabilities of causation can cause clinicians to overlook data that does not fit in with their original...

Using DDSS before getting to know the patient can cause significant 'eccentric' symptoms to be overlooked, as DDSS may bias the practitioner in favor of diagnosing common illnesses. "With all the tools available to modern medicine -- the blood tests and M.R.I.'s and endoscopes -- you might think that misdiagnosis has become a rare thing. But you would be wrong. Studies of autopsies have shown that doctors seriously misdiagnose fatal illnesses about 20% of the time. So millions of patients are being treated for the wrong disease" (Leonhardt 2006). Technology is never a substitute; it is merely a complement for the human side of medicine.
References

Bravata, Sundaram V., K.M. McDonald, W.M. Smith, H. Szeto, M.D. Schleinitz, et al.

(2004, January). Detection and diagnostic decision support systems for bioterrorism response. Emergency Infectious Diseases. [serial online]. Retrieved May 19, 2010. Available from: URL: http://www.cdc.gov/ncidod/EID/vol10no1/03-0243.htm

Leonhardt, David. (2006, February 22).Why doctors so often get it wrong. The New York Times.

Retrieved May 19, 2010 at http://www.nytimes.com/2006/02/22/business/22leonhardt.html