Cardiac Marker Testing: Biomarker Selection and Interpretation Insights

Cardiovascular disease (CVD) is the leading cause of death globally.^1,2 One person dies every 33 seconds from CVD.¹ Cardiac biomarkers are critical in the diagnosis, monitoring, treatment, prognosis and prediction of multiple CVDs.^3,4 This article will take a closer look at cardiac biomarkers, and discuss the criteria for successful biomarker selection.

What are cardiac markers and why are they important?

Defining cardiac markers

Cardiac biomarkers are substances released into the bloodstream when the heart muscle is damaged or stressed due to lack of oxygen.^4,5 

The importance of cardiac markers

Cardiac biomarkers are important because of the information they provide about life-threatening CVDs.^3-5 For example:

• Myocardial infarction, a type of heart attack, is the leading cause of death in the developed world. Cardiac biomarkers play an essential role in diagnosis, risk assessment, guiding management and clinical decision-making for healthcare professionals treating patients with myocardial infarction.⁶
  
  
• Cardiac biomarkers are extremely important for the timely and accurate diagnosis, management and prognosis of acute coronary syndrome, a group of diseases where blood flow to the heart is restricted (including unstable angina and MI). Timely diagnosis enables healthcare professionals to institute therapy early and potentially reverse myocardial damage.^7,8
  
  
• Cardiac biomarkers are used to diagnose myocardial ischemia, a condition that happens when blood flow to the heart muscle is restricted.^5,9

Key cardiac biomarkers

Troponins (cTnI, cTnT) 

Troponins are the most widely used cardiac biomarkers in modern medicine, and are considered the gold standard for diagnosing myocardial infarction.^5,10,11 They are also key cardiac biomarkers for diagnosing acute myocardial ischemia.⁵ 

Troponins enter the bloodstream soon after a heart attack (within two to three hours of a patient’s arrival at the emergency department in most acute MI cases), and they remain in the bloodstream for days after all other biomarkers have returned to normal levels.^5,10

B-type natriuretic peptide (BNP) and N-terminal pro B-type natriuretic peptide (NT-proBNP)

High levels of BNP or NT-proBNP are a sign that the heart is having to work too hard to pump blood. Elevated levels of BNP can be a sign of heart failure.¹²

Myoglobin

Myoglobin is a small protein that stores oxygen. It’s occasionally measured along with troponins to help diagnose a heart attack, but is less specific than troponins.¹⁰

Creatinine kinase (CK) 

CK can be measured several times over a 24-hour period. It will typically at least double that long after a heart attack. However, CK levels can rise in many other conditions besides a heart attack, meaning it’s not a very specific biomarker. CK-MB is a subtype of CK that’s more sensitive for finding heart damage from a heart attack. CK-MB rises four to six hours after a heart attack, but generally returns to normal in a day or two (much sooner than troponins).^5,10

C-reactive protein (CRP) 

CRP is an inflammatory biomarker that can be used as a predictive marker for cardiovascular risk assessment, both on its own and together with other parameters. Highly sensitive assays for measuring CRP have become widely used in personalized or precision cardiology, helping to improve risk assessment and refine therapeutic approaches tailored to individual patients.¹³

The importance of inflammatory biomarkers in cardiology

Inflammation plays a significant role in CVD – it’s a risk factor for CVD and also a treatable symptom of the disease. Recent research has linked chronic low-grade inflammation to coronary artery disease (CAD), and there’s strong evidence that inflammation plays an important role in the development of arterial stiffness.^13-15 

This means that inflammatory markers may be useful additional tools in assessing cardiovascular risk.¹⁵

Key inflammatory markers

High-sensitivity C-reactive protein (hs-CRP) 

hs-CRP indicates low-grade inflammation and cardiovascular risk. It can be used to predict incident myocardial infarction, stroke and peripheral arterial disease.^11,16

Interleukin-6 (IL-6) 

IL-6 reflects systemic inflammation and is linked to atherosclerosis. Research shows that IL-6 family members are also closely related to hypertension, aortic dissection, cardiac fibrosis and cardiomyopathy.^11,17

Tumor necrosis factor-alpha (TNF-α) 

TNF-α is associated with chronic inflammation and cardiovascular disease progression. Studies have shown a relationship between severity of heart failure and levels of TNFα and IL-6.^11,18

Navigating biomarker selection

Criteria for selecting cardiac markers

According to Aydin, et al. (2019), an ideal cardiac biomarker should meet the following criteria:¹⁹

1. Must be sensitive enough to detect a small degree of damage to the heart;
2. Should be specific to the heart muscle (it must exclude damage to other [skeletal] muscles); 
3. Should give information regarding the severity of the infarct and the prognosis of the disease; 
4. Should also show the result of reperfusion therapy in AMI; 
5. Needs to distinguish between reversible and irreversible damage; 
6. Ought not to be detected in patients showing no myocardial damage;
7. Should help in early and late diagnosis; 
8. Should be easy to measure, fast, cheap and quantitative; and 
9. Should have long-term storage conditions and be stable under them.

Guidelines and recommendations for biomarker use

Cardiac troponins (troponin I and troponin T) in the heart are structurally different to those found in skeletal muscle, making them specific and sensitive biomarkers of cardiac myocyte injury. Troponins are recommended as biomarkers for CVD by multiple organizations, including the European Society of Cardiology, the American College of Cardiology, and the American Heart Association. The American College of Cardiology Foundation/American Heart Association Heart Failure guidelines recommend BNP and NT-proBNP for the diagnosis and prognosis of heart failure.^5,7,20

The biomarker recommendations from the 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain are shown below:²⁰

                                                                                                     Gulati et al., 202120

Contact Medix Biochemica’s dedicated sales team to find out more about our cardiology portfolio

Assay methodologies

Common types of assays used in cardiology

• Enzyme-linked immunosorbent assay (ELISA): A technique used to detect and quantify specific molecules by using antigen-antibody interactions and enzyme-linked detection.¹¹ Read more about the ELISA technique.²¹
• Latex particle-enhanced turbidimetric immunoassay (PETIA): A technique that uses latex particles coated with antibodies to detect and quantify specific antigens in a sample. Binding causes a proportional increase in the turbidity (cloudiness) of the solution.¹¹ Read more about the PETIA technique.²²
• Point-of-Care (PoC) testing: Testing done close to the site of patient care, where treatment is being provided. PoC testing provides rapid results. Read more about PoC testing and its usefulness in resource-limited settings.^23,24

When selecting the right type of assay methodology to use, consider:¹¹ 

• Accuracy and precision
• Turnaround time
• Compatibility with clinical workflow (e.g. sample prep time, data analysis requirements, need for specialized instruments, etc.)
  

Reference ranges and interpretation

Establishing reference ranges

A reference range (or “normal range”) is a set of values used by healthcare professionals to determine a patient’s results. The reference range for any given test is based on the results seen in 95% of the healthy population.²⁵

Different factors can affect the reference range, so it may vary for different population groups.²⁵ Factors affecting reference range may include:²⁶

• Race
• Age
• Gender
• Diet
• Body weight
• Smoking habits
• Medication use
• Pregnancy, menopause, or stage in the menstrual cycle
• Manner of sample collection
• Specimen handling and storage
• Method of measurement
  

This is why it’s important to use population-specific reference ranges.

Interpreting results

• Differentiating between normal and abnormal values: Biomarker levels in test results are assessed and compared to the normal reference range, to determine the presence of potential for certain cardiovascular diseases or problems.^5,10-12,20
• Understanding the clinical context: Collected results help assess risk and severity, guide treatment decisions, and monitor disease progression or response to therapy, by indicating the presence and extent of cardiac injury or dysfunction.¹¹
• Serial testing and trend analysis for dynamic assessment: The American Heart Association and European Society of Cardiology guidelines recommend conducting serial cardiac troponin tests to identify and exclude myocardial infarction, and to assess the acuity of a cardiac event in patients with suspected acute coronary syndrome.²⁷

Clinical implications

We can conclude that certain cardiac biomarkers, namely troponins and BNP, are useful and important in diagnosing acute myocardial infarction, managing heart failure and assessing cardiovascular risk.^5,10-12,20

Medix Biochemica provides high-quality raw materials for IVD cardiovascular tests, including antibodies and antigens for cTnI and NT-proBNP. Our animal-free antibodies are manufactured in vitro in cell culture, with no serum or other animal-derived components used during manufacturing. They provide excellent performance and high sensitivity in cardiac assays.²⁸ 

As experts in our field, we also offer recommendations for matched antibody pairs.²⁸

Find out more about what Medix Biochemica can do for you, and be sure to get in touch with us should you have any questions.

References:

1. Heart disease facts. CDC. July 24, 2024. Accessed August 16, 2024. https://www.cdc.gov/heart-disease/data-research/facts-stats/index.html.
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4. Cardiac enzymes (cardiac biomarkers). Cleveland Clinic. Accessed August 16, 2024. https://my.clevelandclinic.org/health/articles/22115-cardiac-enzymes-cardiac-biomarkers.
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11. Expert opinion. Anthony Austin, Global Marketing Manager, Medix Biochemica. July 2024.
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