Diagnoses

In medicine, a diagnosis is the process of identifying a disease or condition by evaluating a patient’s signs and symptoms, medical history, and results from physical examination and tests. A diagnosis serves to guide treatment, prognosis, and communication among clinicians and with patients. Diagnoses may be clinical, based on symptoms alone, or supported by laboratory, imaging, or other objective findings. Clinicians often start with a working or provisional diagnosis and revise it as new information becomes available.

The diagnostic process typically includes taking a detailed history, performing a physical examination, generating a differential diagnosis (a ranked list of plausible conditions), and ordering tests to narrow the possibilities. Once criteria are met, a final or definitive diagnosis may be established; in some cases, a diagnosis remains provisional or uncertain. Some conditions are diagnosed primarily by specific criteria, while others rely on response to treatment or multidisciplinary assessment.

Classification and coding systems, such as the ICD (International Classification of Diseases) and DSM (Diagnostic and Statistical Manual of Mental Disorders), organize diagnoses for clinical, research, and administrative use. Diagnostic accuracy is affected by factors such as test sensitivity and specificity, disease prevalence, and clinician expertise and bias. Errors include overdiagnosis, underdiagnosis, or failure to recognize comorbidity. Patient involvement, second opinions, and adherence to guidelines help improve accuracy.

Diagnoses influence care plans, including treatment choices, monitoring, prognosis, and eligibility for services. They are not always certainties; some conditions may be asymptomatic, evolve over time, or require ongoing reassessment.