Summary

Biomarkers, short for ‘Biological Markers’ are a physical, chemical or biological characteristic that is present in the human body, and measurable too. The measure of one or more biomarkers is an indication of the presence or absence of a disease. Or they indicate the body’s reaction to a drug or therapy. They are indispensable in diagnosing disease, prescribing the right medication, right dosage, and even while designing new drugs. While in the past, biomarkers were few in number, over time, their number has grown significantly. This comes as a boon for doctors and the patient alike. In this article, we will learn more.

Introduction

Diseases have been detected and diagnosed by doctors, throughout the history of mankind, using various physical characteristics seen in the patient and samples taken from his/her body. The colour and thickness of sputum, health of the skin, hair or nails, changes in the fingers and limbs, changes in body-weight, colour of the eyes, changes in colour of urine, changes in stools, location of pain, intensity of pain, pulse rate, heart rate, blood-pressure, sugar level, etc, etc have all been used by native doctors across the world, to diagnose disease.

The industrial revolution brought along with a Healthcare revolution in the 18^th, 19^th and 20^th centuries. Various instruments were invented to measure one or more health parameters. Advances in molecular biochemistry led to the discovery of various medicines and vaccines. Today, pharma and healthcare are extremely sophisticated sectors, and highly technology-driven.

Doctors and research scientists can isolate biomarkers quickly and with ease. More and more biomarkers are being added to the roster of diseases every year. This is making detection and diagnosis of diseases easier, designing and developing new drugs easier, efficient and effective treatment of the patient easier. It wouldn’t be wrong to say that today, much of medicine and healthcare is built on the foundation of biomarkers.

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Why are Biomarkers important?

Biomarkers are associated with all of these roles. They….

• Help measure the progress of a disease
• Assess the most effective therapy for a particular sub-type of the disease
• Establish long-term vulnerability to a particular disease
• Establish the risk of relapse
• Map the progression of a disease from early-stage to end-stage
• Establish severity of a disease, which makes it easy to predict the outcomes, determine the required treatment options and assess the responses to therapy
• Establish the relationships between environmental risk-factors
• Are critical for early diagnosis and prevention of a disease
• From a pharmacological perspective, they are required for drug target identification and drug response evaluation

The advantages of having biomarkers are:

• Precise measurements can be done
• Its more economical, in contrast to endless research
• There is less bias and human error than what is possible with questionnaires
• They act as rapid warning signals which leads to quick interventions
• They are reliable, which means, their validity can be established
• The risk or severity of a disease is more homogenous
• Disease mechanisms can be better studied and understood using biomarkers
• Objective assessment of a condition

What qualifies as a biomarker?

The WHO defines a biomarker as “any measurement reflecting an interaction between a biological system and a potential hazard, which may be chemical, physical, or biological. The measured response may be functional and physiological, biochemical at the cellular level, or a molecular interaction”.

To a layman, biomarkers may appear the same as signs and symptoms of a disease (such as temperature and heart-rate). However, the medical fraternity is clear on what qualifies as a biomarker. An ideal biomarker should have as many of the below attributes as possible:

• It should be safe and easy to measure, any attempt to measure it must not lead to new complications
• It must be cost-efficient to follow up, and not require complicated procedures or instrumentation for the same
• It must be modifiable with treatment, in a predictive manner
• It must be consistent across gender and ethnic groups
• It must be reliable, that is, no matter how many times a particular biomarker is employed, it must show consistent results
• It should be sensitive to treatment or environmental factors, and specific to a particular condition
• It must be consistently applicable to diagnosis, staging and prognosis

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Types and Classification of Biomarkers

Over the years, as more and more biomarkers were added or identified by the medical fraternity, they have been classified in different ways.

Based on their source or location

1. Molecular – have biophysical properties, which allow their measurements in biological samples such as blood plasma, serum, cerebrospinal fluid, bronchoalveolar lavage, biopsy, urinalysis and faecal analysis
2. Radiographic – obtained from imaging studies, example – bone mineral density
3. Histologic – reflect biochemical or molecular alteration in cells, tissues or fluids, example – the staging and grading of cancers
4. Physiologic – measures of body processes, example – blood pressure, pulse rate and heart-rate

Based on roles/functions

Susceptibility/Risk Biomarkers

As the name implies, these biomarkers indicate the person’s likelihood of developing a particular disease or condition in the near or distant future. Example:

• Mutations in the BRCA1 and BRCA2 genes: These are associated with a higher risk of developing breast and ovarian cancer. So, testing for these mutations can identify persons who may require more surveillance, risk-reducing surgeries and targeted therapies, either now, or in the near future.

Diagnostic Biomarkers

These are used to detect or confirm a particular disease or condition. They can also reveal the nature of the disease. Examples:

• Prostate-specific antigen (PSA): High levels of this antigen in the blood, is an indicator of prostate cancer in a man. Monitoring the change in PSA levels is used to monitor the progression of the disease or response to treatment.
• C-reactive protein (CRP): This protein is used to evaluate inflammation levels in the body. Various conditions such as cardiovascular diseases, lupus and rheumatoid arthritis cause inflammation, so this biomarker can be used to detect, confirm and monitor these conditions.

Prognostic Biomarkers

In people who already are confirmed to have a disease, prognostic biomarkers can predict the likelihood of disease progression or relapse. Examples:

• Ki-67: This protein is an indicator of cell-proliferation. High levels of this protein can indicate an aggressive tumour and worsening condition. So, its used as a biomarker in breast, prostate and other cancers.
• BRAF: This is a gene that is generally mutated in patients with melanoma and other cancers. BRAF inhibitors are a targeted therapy for such people. So, this biomarker is used to predict the response of the patient to such therapies. This way, they can receive early treatment.

Monitoring Biomarkers

These biomarkers are used for one or all of these reasons: to assess the stage or condition of the disease, to measure the exposure to a particular drug, and to measure exposure to an environmental agent. So, monitoring them is important for managing and treating the disease.

Examples:

• Haemoglobin A1c (HbA1c): This is a popular biomarker used to monitor severity or progression of diabetes, and the response to treatment. HbA1c levels in the blood indicate the average blood-glucose level in the last three months.
• Brain natriuretic peptide (BNP): This peptide is released by the heart in response to an increase in blood-pressure and blood-volume, which are common events during a heart failure. So, monitoring BNP levels can identify the severity of heart failure and decide the treatment options.

Predictive Biomarkers

These are used to identify individuals who have a higher likelihood of experiencing a strong outcome (either favourable or unfavourable) when exposed to a particular drug or environmental agent. This will help decide the treatment options. Examples:

• HER2/neu protein and breast cancer: HER2/neu protein levels are higher in people with some types of breast cancer. So, testing for this protein can help predict the outcome of targeted therapies such as the drug trastuzumab. This way, they can receive the drug early on, and cure sooner.
• EGFR mutation and non-small-cell lung cancer: EGFR is a gene that is generally mutated in people with non-small-cell lung cancer (NSCLC). Patients with EGFR mutations may show more favourable outcome to targeted therapies such as gefitinib (Iressa) and erlotinib (Tarceva), and hence benefit from earlier treatment using these drugs.

Pharmacodynamic/Response Biomarkers

These reveal that a biological response has happened in patients exposed to a particular drug or environmental agent. So, these are used in clinical trials to assess the effectiveness of the drug. Examples:

• Measurement of tumour size in response to chemotherapy or radiation.
• LDL-cholesterol levels and statin drugs: Statins are a category of drugs used to lower cholesterol-levels in patients with high cholesterol-levels in the blood. So, when these drugs are given, the reduction in LDL (low-density lipoprotein) cholesterol levels is used as a biomarker to evaluate response to treatment.
• Blood-pressure and antihypertensive drugs: Antihypertensive drugs are given to patients of hypertension to lower their blood-pressure. So, the reduction in blood-pressure is used as a biomarker to assess response to such drugs.

Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai, Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.

Chennai – Alwarpet/Vadapalani 044 4000 6000 • Trichy – Cantonment – 0431 4077777 • Trichy – Heartcity – 0431 4003500 • Trichy – Tennur – 0431 4022555 • Hosur – 04344 272727 • Salem – 0427 2677777 • Tirunelveli – 0462 4006000 • Bengaluru – 080 6801 6801

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