Biomarker, in medicine, is a substance whose detection in the body provides important information about a patient’s condition. Physicians usually detect biomarkers through blood or urine tests. The detection of a particular biomarker may indicate that the patient has a certain disease. A biomarker may also suggest how a particular disease may progress or respond to treatment. In some cases, biomarkers help physicians predict which treatments may be most effective and which treatments may not work well.
Biomarkers are particularly useful for detecting certain types of heart disease and cancer. For example, a protein called troponin serves as an important biomarker of heart damage. When heart muscle is injured, as it is in a heart attack, troponin leaks out of the damaged cells. Physicians can thus detect a recent heart attack through elevated levels of troponin in the bloodstream. Physicians may diagnose prostate cancer with a blood test that measures a protein called prostate-specific antigen (PSA). Elevated levels of PSA may suggest prostate cancer, with the likelihood of the disease greater the higher the level.
Physicians can also use biomarkers to measure the success of a course of treatment. For example, they often measure the level of a hormone called brain natriuretic peptide (BNP) in the blood to determine how well a patient’s heart is working. Normally, only a relatively low amount of BNP is found in the blood. But in certain conditions, such as heart failure, the heart releases more BNP into the bloodstream. When heart failure has been effectively treated, the level of BNP in the bloodstream returns to normal. Scientists are working to identify other substances and even combinations of genes that can serve as biomarkers.
