What is a biomarker? Biomarkers are biological measures of health or disease and are a cornerstone for personalized medicine.Historically, diagnosing a disease was based on symptoms. This reminds me of a joke. A patient goes to see the doctor and tells him “Doctor, I hurt everywhere.” The patients touches his head “I hurt here”, he touches his arm “I hurt here”, he touches his stomach “I hurt here” and on and on. The doctor looks at him and says “I know what’s wrong with you! You have a broken finger!”
No one wants to be diagnosed or misdiagnosed with a broken finger. This isn’t to say understanding symptoms and using this information to contribute to a diagnosis isn’t important. But what if…
…symptoms don’t lead to an obvious diagnosis?
…two patients have the same symptoms, but different diseases?
…two patients have the same disease, but different causes – either the root cause is different or they both have lung cancer but the genetic mutations in each cancer is different. In this case different treatments would be are needed.
…two patients have different diseases, but similar causes – maybe they both have the same genetic mutation in two different kinds of cancer – so the same treatment can be used?
This is where biomarkers come in. Biomarkers are things in the body that can be measured to give us information about a disease or other condition. Biomarkers can be a variety of things including
- Imaging methods
- Genes (presence or absence)
- Specific gene mutations
- Proteins or antibodies
And these things can be measured to in some way indicate if the person is healthy or has a disease. Other biomarkers may be used to detect a disease earlier than when the patient is showing symptoms. Detecting a disease early may allow the patient to change a behavior to decrease the likelihood of developing the disease or to start treating a patient earlier when it is easier to successfully treat a disease. Biomarkers may also be used to determine the severity of a disease or whether or not the disease is progressing.
Some biomarkers that you may be familiar with are cholesterol, temperature, and blood pressure. There are a number of biomarkers for pregnancy. Home pregnancy tests look for the presence of the protein beta human chorionic gonadotropin (also called beta-HCG) in the urine. This protein biomarker is in the blood after the zygote implants 6-12 days after fertilization. Other biomarkers such as serum creatinine and liver enzymes are markers for kidney and liver function, respectively.
So what makes a good biomarker? First, it needs to be different if the patients has a disease. For example, higher than normal blood glucose levels may indicate that a patient has diabetes and these levels of blood glucose would not be found in a patient who didn’t have diabetes. Second, the biomarker would have to correlate with the outcome. What this means is that as the patient’s condition changes, the biomarker would also change. In the case of the patient with high blood glucose and diabetes, when the patient starts regulating their diet or taking insulin, the blood glucose levels will go down. Third, biomarkers should be easy to access, and one of the main reasons for this is so that testing for the biomarkers isn’t too expensive. Blood is a common location for biomarkers, including in our example of blood glucose levels. Finally, biomarkers should be consistent. It wouldn’t be useful to have a biomarker that changes based on whether it’s noon or midnight. It needs to be dependent on the health of the patient.
Biomarkers are a cornerstone of personalized medicine because they allow clinicians to use symptoms along with measurable and quantifiable factors in the body (the biomarkers) to diagnose, track, and treat disease. Learn more about biomarkers in this YouTube video