A blood marker is any component in the blood that's associated with a condition, disease or symptom. Doctors look for something in the blood that they know affects, or is affected by, something else. Blood markers can indicate whether a system is healthy and functioning properly or if there's something wrong. Blood markers can be hormones, proteins, steroids, or enzymes, for instance.
A 2001 study revealed two new blood markers that may enhance doctors' ability to predict a person's risk of heart attack. Most doctors measure "good" and "bad" cholesterol -- both belonging to the steroid class of markers -- to assess risk, but can miss some fatty cells. The study focused on two markers known as triglyericides: a form of fat that stores energy in fatty tissue and releases it gradually into the bloodstream between meals to meet the body's energy needs. Measuring those along with cholesterol could help provide a more accurate measurement of cholesterol levels in the bloodstream. Scientists have also discovered that the presence of a certain sugar protein in the blood can be used to monitor patients with cancer, although it is not used for diagnosis.
In recent years, several studies have shown that higher amounts of proteins in the blood may be associated with various diseases. Identifying such biological markers as early as possible, before the onset of symptoms, could lead to earlier and better diagnoses, and earlier treatment. For instance, if elevated concentrations of certain neural growth "markers" are present at birth, it may be an indication that autism or mental retardation will develop later in childhood. Such growth factors play an important role in producing new brain cells and organizing them into networks.