Biomarkers in clinical samples

The word ‘Biomarkers’ is a combination of ‘biological’ and ‘markers’ and refers to the various indicators that we can use to detect the processes happening inside a person.

These processes can range from pregnancy to serious illnesses. By detecting the levels and changes of these biomarkers, we can measure and map the progression of biological processes, as well as identifying possible treatments or taking preventative measures.

Biomarkers cover a vast range of indicators. The most commonly used biomarkers are often related to the vital signs of a patient, such as temperature, blood pressure, and heart rate. These systemic biomarkers are often much easier to measure and have been used for centuries to determine the health of a patient; however, they often do not precisely describe what is wrong with a patient. For example, if you have a raised temperature, this can indicate that you have an illness such as the flu, but a rise in body temperature can indicate many other illnesses. Therefore, these types of biomarkers are useful for determining a patient’s overall condition but are often not suitable for determining which treatments are suitable.

To reliably identify a patient’s illness, specific biomarkers have to be used. Generally, the more specific the biomarker, the more detail that can be learned about the affecting disease or process. There are many different types of specific biomarker that we can measure. These often include markers such as cells, proteins, genes, and chemicals.

For example, in order to diagnose pregnancy, we can look for the presence of human chorionic gonadotropin (hCG) proteins. These proteins are very specific and are only usually present in those patients who are pregnant.

Another example is in the diagnosis of glandular fever, or the ‘kissing disease’. This disease is caused by a virus known as the Epstein-Barr virus and can cause a variety of symptoms such as a fever and swollen glands. These symptoms can be present in many other illnesses, such as the common flu. Therefore, to check whether glandular fever is the cause, a doctor can test the patient’s blood for specific white blood cells and antibodies, which are only produced when the Epstein-Barr virus is present.

For many diseases and illnesses, we can look for these indicative proteins and molecules. Therefore, by determining specific biomarkers that are unique to particular diseases, we can more reliably diagnose patients and allow for tailored treatment.

Biomarkers can be used to determine the health of a patient at many different stages. According to the Food and Drug Administration (FDA) and the National Institutes of Health (NIH), there are seven categories that biomarkers fall into depending on their application:

• Susceptibility/Risk biomarkers are used to determine a patient’s chance of developing a certain disease. For example, high levels of cholesterol in the blood indicates a higher risk of certain heart diseases. By using these types of biomarker, we can use preventative measures to help patients.

• Diagnostic biomarkers are the most common type. These are used to determine whether or not a patient has a particular condition. For example, glucose levels in the blood can be used to determine whether a patient has diabetes. By diagnosing the specific disease affecting the patient, correct treatment can be given.

• Monitoring biomarkers can be assessed over time. By detecting the levels and changes in these biomarkers, we can monitor whether a patient’s condition is improving over time or whether they are responding to particular drugs.

• Prognostic biomarkers identify the possibility that a particular clinical event will occur. For example, measuring C-reactive protein levels in patients who have suffered a heart attack can determine whether or not the patient is likely to have further problems.

• Predictive biomarkers are very similar to susceptibility/risk biomarkers. However, they predict whether a patient is likely to have favourable/unfavourable effects from a particular treatment, rather than the risk of developing a new disease. For example, certain patients with HIV carry a gene which means a certain antiviral drug can cause severe skin reactions.

• Pharmacodynamic/Response biomarkers often fall under the category of monitoring biomarkers as they can be measured over time. These biomarkers are used to determine whether a medical intervention has been effective. An example of this is measuring the blood pressure of a patient who has been given medication to combat hypertension (High blood pressure).

• Safety biomarkers are used to determine whether or not particular drugs are having these effects on the patient. For example, certain antibiotics can affect the functionality of the kidneys. By measuring levels of creatine in the body, the safety of the patient can be ensured.

So now you know about the various molecules and cells that can be used to determine a patient’s condition, in the next step we ask “how do we actually detect these biomarkers?”