What is the Difference Between CK and CPK Blood Test

The key difference between CK and CPK blood test is that the CK blood test detects the presence of creatine kinase while the CPK blood test detects the presence of creatine phosphokinase in the bloodstream.

Creatine kinase (CK) and creatine phosphokinase (CPK) are two enzymes in the body. They are mainly found in the skeletal muscles, heart, and brain. CK and CPK enzymes catalyze the conversion of creatine using ATP to make phosphocreatine and ADP. This process is also known as the phosphorylation of creatine. There are three types of CK enzymes: CK-MM, CK-MB, and CK-BB. CK-MM is mostly present in skeletal muscles, CK-MB is mostly present in heart muscles, and CK-BB is mostly found in brain tissue. There are also three types of CPK enzymes: CPK 1 or CPK-BB, CPK 2 or CPK-MB, and CPK 3 or CPK-MM. CPK 1 is mostly found in the brain while CPK 2 is mainly found in the heart, and CPK 3 is mainly found in skeletal muscles.

CONTENTS

1. Overview and Key Difference
2. What is CK Blood Test
3. What is CPK Blood Test
4. Similarities – CK and CPK Blood Test
5. CK vs CPK Blood Test in Tabular Form
6. Summary – CK vs CPK Blood Test

What is CK Blood Test?

Creatine kinase or CK blood test is a test that measures the amount of creatine kinase enzyme in the blood. CK is an important enzyme required for the production of energy and muscle function. It is an enzyme that is mostly found in the skeletal muscle and heart. A small amount of CK in the blood is normal; however, higher amounts depict health problems depending on the type and level of CK found in the blood. They can indicate any damage or disease of the skeletal muscles, heart, or brain. CK blood tests are often used to monitor and diagnose muscular injuries and diseases. A few examples of such diseases are muscle dystrophy, which is a rare inherited disease-causing muscle weakness and loss of function, mostly in males, and rhabdomyolysis, which is a rapid breakdown of muscle tissue. This blood test also helps in diagnosing heart attacks in some instances. Doctors usually prescribe a CK test in the presence of symptoms such as muscle pain, muscle weakness, balance issues, numbness, or tingling.

A CK test is carried out using a blood sample from a vein. Males usually have higher CK values than females because males have a high muscle mass. The lower normal limit for males and females is approximately 20-30 units per litre. The normal upper limit for males ranges between 200-395 units per litre, and for females, it is up to 207 units per litre. High CK-MM shows muscle injuries or diseases, high CK-MB shows inflammation in the heart muscles or heart attack, and high CK-BB shows brain injury or a stroke. Other conditions that cause higher CK levels are obesity, underlying health issues, blood clots, hormonal disorders, infections, medical interventions, strenuous exercises, and some medicines. People with high CK levels show symptoms such as cramps, muscle pain and weakness, fatigue, dark urine, and inability to exercise.

What is CPK Blood Test?

Creatine phosphokinase or CPK blood test is a test that determines the levels of creatine phosphokinase enzyme in the blood. Creatine phosphokinase is an important enzyme found in skeletal muscles, heart, and brain tissue in order to carry out energy production and efficient muscle function. The CPK blood test is carried out using a blood sample from a vein. This procedure is known as venipuncture. The CPK test is usually used in diagnosing heart attacks, detecting the cause of chest pain, assessing the extent of damage to heart or muscle tissues, and determining muscular dystrophy. CPK blood tests detect various diseases such as dermatomyositis, polymyositis, malignant hyperthermia, and muscle breakdowns. They do not have any special requirements, such as fasting prior to the test. However, certain medications such as cholesterol-lowering drugs, anaesthetics, steroids, and amphotericin B interfere with the results of the CPK blood test. Over-exercising, medical interventions, intramuscular injections, cardiac catheterization, and vaccines also show elevated CPK levels.

High CPK 1 is mainly found in the brain and indicates brain injury, brain cancer, or seizures. High CPK 2 is mainly found in the heart and indicates heart injury, inflammation in the heart, electrical injury, and heart attack. High CPK 3 levels are mainly found in skeletal muscles and indicate muscle inflammation, muscle injuries, damage, muscle dystrophy, muscle trauma, and electromyography. CPK blood test results vary from males to females. The normal range for males is between 39-308 units per litre, and for females, it is between 26-192 units per litre.

What are the Similarities Between CK and CPK Blood Test?

• CK and CPK tests are blood tests.
• Both tests are carried out using blood from veins.
• Moreover, they detect the presence of the respective enzymes in the blood.
• Both tests detect any damages, diseases, or health problems in skeletal muscles, the heart, and the brain.
• They do not require fasting or any other special requirement prior to taking blood.
• Conditions such as medical interventions, over-exercising, and some medicines increase levels of CK and CPK in the test results.
• In both tests, males show a higher amount of enzyme levels than females.

What is the Difference Between CK and CPK Blood Test?

CK blood test detects the presence of creatine kinase, while CPK blood test detects the presence of creatine phosphokinase in the blood. Thus, this is the key difference between CK and CPK blood test. For females, the limit for the CK test is 20-207 units per litre, while the limit for the CPK test is 26-192 units per litre. Meanwhile, for males, the limit for the CK test is 20-395 units per litre, and the limit for the CPK test is 39-308 units per litre.

The below infographic presents the differences between CK and CPK blood test in tabular form for side-by-side comparison.

Summary – CK vs CPK Blood Test

Creatine kinase (CK) and creatine phosphokinase (CPK) are two enzymes in the body. They are mainly found in the skeletal muscles, heart, and brain. They catalyze the phosphorylation of creatine. CK blood test detects the presence of creatine kinase, while CPK blood test detects the presence of creatine phosphokinase in the bloodstream. Creatine kinase blood test measures the CK-MM, CK-MB, and CK-BB, and the presence of these enzymes detects health problems or damage in skeletal muscles, heart, and brain tissue, respectively. CPK test measures CPK 1, CPK 2, and CPK 3, and the presence of these enzymes detects any damage or problem in the brain, heart, and skeletal muscles, respectively. So, this summarizes the difference between CK and CPK blood test.

Reference:

1. “Creatine Kinase: Medlineplus Medical Test.” MedlinePlus, U.S. National Library of Medicine.
2. “Creatine Phosphokinase Test.” Mount Sinai Health System.

Image Courtesy:

1. “Brain Creatine Kinase, restype ID” By Hibby – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Laboratory-medical-medicine-hand” (CC0) via Pixabay