Accurate Diagnosis Is Imperative
An ill person has three fundamental questions: (1) What is happening to me and why? (2) What does this mean for my future? (3) What can be done about it? Providing answers to these questions are the three timeless tasks of the healing professions: explanation, prognostication, and treatment. This has been true across time and cultures, regardless of the belief system underpinning the culture: magic, faith, rationalism, or science. Accurate explanation, prognostication, and appropriate treatment require precise diagnosis. The history and physical exam are the basis for diagnostic hypothesis generation, the first step in the diagnostic process.
Knowledge, an understanding of clinical epidemiology, and experience are necessary to determine when pursuit of specific symptoms and signs is warranted. For common minor complaints in healthy people without alarm symptoms, a good prognosis can be assumed without knowing the exact cause, as, for instance, an upper respiratory infection (URI). The patient can be reassured that further testing will not change prognosis or treatment. When the diagnosis is not self-evident from the initial symptoms, or the course deviates from what is expected, a more exacting diagnostic evaluation becomes necessary.
In the process of making a diagnosis, the clinician makes a series of inferences about the nature of bodily dysfunction. When making these inferences from clinical data, clinicians use many strategies to combine, integrate, and interpret the data. After collating the data, the next step in the diagnostic process is generation of one or more diagnostic hypotheses. A hypothesis is sometimes generated merely from a patient’s age, sex, race, appearance, and presenting complaint. On the other hand, hypotheses may emerge exclusively from a physical finding or laboratory data. New hypotheses are triggered as new findings emerge. Diagnostic hypotheses can be general (infection or inflammation) or quite specific (acute right ventricular myocardial infarction). Diagnostic reasoning proceeds by progressively modifying and refining the hypotheses. This inferential reasoning process continues until the clinician arrives at a working diagnosis, a diagnostic hypothesis sufficient to establish a prognosis and direct therapeutic intervention. The hypothesis should yield accurate predictions of test results and the patient’s future clinical course.
A diagnostic hypothesis provides entry to the medical literature for current information about etiology, diagnostic findings, prognosis, and treatment. Recurring patterns of disordered bodily structure, function, and mentation suggest a common cause. When a shared pathophysiology and etiology are confirmed, the condition is a disease. Combinations of features not clearly related to a single cause are syndromes. Diseases and syndromes are intellectual constructs that do not exist independently of the patients who manifest them. These constructs allow aggregation of patients with relatively homogeneous physiologic disorders for study to promote understanding of disease and to evaluate potential treatments. Accurate diagnosis is indispensable for initiating treatment.