Screening and surveillance are words that are often encountered in the practice of medicine.
Are they synonymous or strictly different? Personally, I think they are strictly different.
Medical screening, in the strictest sense, is a method for detecting disease or body dysfunction before an individual would normally seek medical care. It is done in patients with no signs or symptoms of a disease or body dysfunction. For example, screening physical examination of the breast, mammography or ultrasound is done in patients with no signs or symptoms suggestive of a disease associated with the breasts – no pain, no mass, no lesion, etc. Another example, screening physical examination of the thyroid gland or ultrasound of the thyroid gland is done in patients with no signs or symptoms suggestive of a disease associated with the thyroid gland. Still another example, a screening colonoscopy is done patients with no signs or symptoms suggestive of a large intestinal disease.
Medical surveillance is a method of close observation or monitoring. Strictly speaking, it is done in the following situations:
- After something unusual is found on medical screening and there is a need to closely observe or monitor the findings in order to get to a more definite diagnosis.
- After a definite medical condition is found on medical screening and there is a need to closely observe or monitor it as it does not require an active treatment at the moment, the so-called expectant management or watch and wait management.
- After a treatment of a definite medical condition has been done (regardless of whether this medical condition was found on medical screening or not) and there is a need to closely observe and monitor for persistence or recurrence of the medical condition.
Examples of medical surveillance after finding and initial treatment of a medical condition include the following:
- After primary treatment of a breast cancer, doing medical surveillance to closely observe or monitor for persistence or recurrence of breast cancer.
- After seeing multiple nodules in an ultrasound of the thyroid in which the primary diagnosis is multiple colloid adenomatous goiter and doing medical surveillance to closely observe or monitor for signals of thyroid cancer.
- After doing a colonoscopy for medical screening in a patient with absence of signs or symptoms, a polyp was found. Doing follow-up colonoscopy after the medical screening to closely observe or monitor the status of the polyps, whether progressing or not, or whether there is a recurrence after it has been removed previously is considered medical surveillance, not screening anymore.