Teori Praktikum: Pengukuran Enzim CK-MB

Summary

The video script discusses the clinical analysis of CK-MB (Creatine Kinase-MB), an enzyme used in diagnosing acute myocardial infarction (heart attack). It covers the enzyme's significance, measurement methods, kinetics, and diagnostic value. The speaker explains CK-MB's release patterns post-heart attack and how its levels are affected in various conditions like skeletal muscle trauma and chronic kidney disease. The presentation also goes into the technical details of reagent preparation, the principle of the kinetic method, the use of photometers, and troubleshooting common lab errors. It emphasizes the importance of accurate measurements for reliable results.

Takeaways

• 🧪 CK-MB is an isoenzyme used widely for diagnosing heart function, particularly acute myocardial infarction (AMI), since the 1960s.
• 🕒 CK-MB levels rise 3-4 hours after a heart attack and stay elevated for about 65 hours, with 50% accuracy after 3 hours and 90% accuracy after 6 hours.
• 🔬 Advances in technology have made the measurement of CK-MB more precise, moving from qualitative to quantitative measurements.
• 💉 High CK-MB levels can also appear in patients with acute skeletal muscle trauma (59%) and chronic muscle disease (78%).
• ⚖️ CK-MB makes up a small percentage of total creatine kinase (CK), about 0-3% in skeletal muscles and around 20% in cardiac tissue.
• 📊 CK-MB is crucial for diagnosing myocardial infarction due to its specific release pattern after a heart attack.
• 🧫 The CK-MB measurement process uses specific reagents and tools, including hexokinase and glucose-6-phosphate dehydrogenase, to detect NADPH levels at 340 nm wavelength.
• 🧬 Reagents used in the test are costly due to their complex composition, and need to be stored properly to maintain stability.
• 🔍 The testing involves careful measurement steps, including incubation at 37°C and precise absorbance readings at specific intervals.
• ⚠️ Errors in CK-MB testing can arise from issues such as hemolysis, incorrect wavelength, improper reagent volumes, and expired reagents, which can affect the accuracy of results.

Q & A

What is CK-MB and its role in medical diagnostics?

CK-MB is a specific isoenzyme of creatine kinase (CK) that is primarily found in heart muscle cells. It is used as a biomarker for diagnosing acute myocardial infarction (heart attack) as it is released into the bloodstream after heart muscle injury.

Why has CK-MB been considered the gold standard for diagnosing heart attacks since the 1960s?

Since the 1960s, CK-MB has been widely accepted as the gold standard because of its specificity to heart muscle damage, making it highly reliable for diagnosing acute myocardial infarction. Advances in technology have further improved the precision of CK-MB measurement.

How soon can CK-MB levels be detected after the onset of heart attack symptoms?

CK-MB levels can be detected as early as 3-4 hours after the onset of heart attack symptoms, and they remain elevated for up to 65 hours post-infarction, making it a useful early marker.

What are the common sources of interference in CK-MB measurements?

CK-MB levels can be affected by other conditions such as skeletal muscle trauma, chronic muscle diseases, and chronic kidney failure, which may lead to false positives or variations in test results.

How does CK-MB measurement differentiate between cardiac and skeletal muscle injury?

CK-MB is primarily associated with the heart muscle, but a small percentage is also found in skeletal muscle. However, its ratio in heart muscle is much higher (around 20% of total CK), compared to skeletal muscle (0-3% of total CK). This helps differentiate between cardiac and skeletal muscle injury.

What is the principle behind the kinetic method used for CK-MB measurement?

The kinetic method for CK-MB measurement involves using antibodies that bind specifically to CK-MB isoenzymes. The reaction is monitored by measuring the formation of NADPH, which absorbs light at 340 nm, indicating enzyme activity.

What are the reagents used in the CK-MB test, and why are they important?

Reagents in CK-MB testing include anti-human CK-MB antibodies, creatine phosphate, ADP, and glucose-6-phosphate dehydrogenase, among others. These reagents are essential for facilitating the enzymatic reactions and ensuring accurate measurement of CK-MB levels.

How does the CK-MB measurement remain stable over time, and what are the storage conditions?

CK-MB reagents remain stable when stored at 2-8°C for up to 15 days. They should be kept away from direct sunlight to prevent degradation, which ensures the accuracy and reliability of the test results.

What is the role of absorbance in the CK-MB test, and how is it measured?

Absorbance in the CK-MB test measures the concentration of NADPH, which correlates with CK-MB enzyme activity. The higher the absorbance at 340 nm, the higher the CK-MB levels. Absorbance is measured using a photometer at specific intervals.

What are the potential errors in CK-MB testing, and how can they be avoided?

Common errors in CK-MB testing include hemolysis, incorrect wavelength settings, excessive physical activity before testing, incorrect reagent volumes, improper incubation times, and expired reagents. These can be avoided by following proper laboratory protocols.