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A liquid biopsy, also known as fluid biopsy or fluid phase biopsy, is the sampling and analysis of non-solid biological tissue, primarily blood. [1] [2] Like traditional biopsy, this type of technique is mainly used as a diagnostic and monitoring tool for diseases such as cancer, with the added benefit of being largely non-invasive.
The Food and Drug Administration (FDA) has recently approved a blood test screening for colorectal cancer that has an over 83% success rate at detecting the presence of this form of cancer.
The objective of cancer screening is to detect cancer before symptoms appear, involving various methods such as blood tests, urine tests, DNA tests, and medical imaging. [ 1 ] [ 2 ] The purpose of screening is early cancer detection, to make the cancer easier to treat and extending life expectancy. [ 3 ]
Selection bias may also make a test look better than it really is. If a test is more available to young and healthy people (for instance if people have to travel a long distance to get checked) then fewer people in the screening population will have negative outcomes than for a random sample, and the test will seem to make a positive difference.
For example, the ColoGuard test may be used to screen people over 55 years old for colorectal cancer. [57] Cancer is a longtime-scale disease with various progression steps, molecular diagnostics tools can be used for prognosis of cancer progression. For example, the OncoType Dx test by Genomic Health can estimate risk of breast cancer.
Fecal occult blood testing (FOBT), as its name implies, aims to detect subtle blood loss in the gastrointestinal tract, anywhere from the mouth to the colon.Positive tests ("positive stool") may result from either upper gastrointestinal bleeding or lower gastrointestinal bleeding and warrant further investigation for peptic ulcers or a malignancy (such as colorectal cancer or gastric cancer).
[6] [7] For example, analysis of blood samples from cancer patients has found a propensity for increased CTC detection as the disease progresses. [8] Blood tests are easy and safe to perform and multiple samples can be taken over time. By contrast, analysis of solid tumors necessitates invasive procedures that might limit patient compliance.
Reflect the stage of cancer; By determining the stage of cancer, it's possible to give a prognosis and treatment plan. [4] Screening for cancers; No screening test is wholly specific, and a high level of tumor marker can still be found in benign tumors. The only tumor marker currently used in screening is PSA (prostate-specific antigen ...