A sign is an objective indication of a disease or condition that can be observed or measured by a healthcare provider, as opposed to a symptom, which is reported by the patient.
Explanation
Clinicians rely on signs to recognize and monitor illness because they provide measurable evidence of abnormal physiology. Signs may be detected during a physical examination—such as jaundice, cyanosis, edema or abnormal heart sounds—or captured by monitoring devices and laboratory tests, like elevated body temperature, high blood pressure, or a positive blood culture. Vital signs (temperature, pulse, respiratory rate and blood pressure) are routinely recorded to assess a person’s basic physiological status. Some signs are pathognomonic, meaning they are highly specific for a particular disease; for example, Koplik spots inside the mouth indicate measles. Others are nonspecific but help narrow the differential diagnosis when considered alongside symptoms and patient history. Objective signs are essential for screening, diagnosing diseases, gauging severity and evaluating the response to treatment. They also form the basis for clinical scoring systems that guide management of sepsis, heart failure and other conditions.
Categories and Examples
- Vital signs: body temperature, heart rate, respiratory rate and blood pressure measured to assess homeostasis.
- Physical examination signs: rash, jaundice, cyanosis, abnormal lung sounds, abdominal tenderness or neurological deficits detected by inspection, palpation, percussion and auscultation.
- Laboratory and imaging signs: abnormal white blood cell count, elevated serum creatinine, chest radiograph infiltrates or electrocardiogram changes.
- Pathognomonic signs: e.g., Koplik spots in measles, the bull’s-eye rash of Lyme disease or the “cherry red” spot in Tay–Sachs disease.
- Signs differ from symptoms such as pain or fatigue, which are subjective sensations reported by the patient.
Recognizing and interpreting signs allows healthcare providers to make informed diagnoses, monitor disease progression and tailor therapy. Signs complement patient‑reported symptoms to build a complete clinical picture.
Related Terms: Symptom, Vital Signs, Diagnosis, Pathognomonic Sign, Physical Examination