Diagnosis: Fundamental Principles and Methods.

Problem-solving is an essential human endeavor. It involves problem definition, followed by solution design, solution implementation, and, finally, review. Healthcare is a prime and often successful example of problem-solving. In medical terminology, the problem definition is termed the diagnosis, the solution design is called the treatment plan, and the solution itself is the provision of treatment. The case review is used to assess the efficacy of the solution. This process is sequential and consequential. Obviously, if a problem's definition is absent or incorrect, then an appropriate solution cannot be designed or implemented. Unfortunately, missed or incorrect diagnoses are not uncommon in healthcare and can cause considerable harm and economic cost. Minimizing these diagnostic errors would confer great benefits to patients, clinicians, and healthcare organizations. Understanding the nature of diagnosis and why it can be so difficult are some of the first steps in reducing these diagnostic errors. One issue is that diagnosis may seem to be more of an art than a science when the exact mechanisms of diagnosis are often not clearly described. Clinicians typically learn their diagnostic craft by mimicry of their mentors over years of hard experience. This absence of a clear method not only makes diagnosis difficult to do well it also makes diagnosis difficult to teach well. The purpose of this paper is to try to better articulate the fundamental principles and methods of diagnosis and to make diagnosis more intellectually understandable, and so more teachable, and more achievable by clinicians.