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Questions and Answers
Which enzyme is primarily associated with liver function and is abbreviated as ALT?
Which enzyme is primarily associated with liver function and is abbreviated as ALT?
- Gamma glutamyl transferase
- Creatine kinase
- Aspartate aminotransferase
- Alanine aminotransferase (correct)
What condition may lead to increased levels of alkaline phosphatase (ALP) in the blood?
What condition may lead to increased levels of alkaline phosphatase (ALP) in the blood?
- Myocardial infarction
- Liver cirrhosis
- Bone healing (correct)
- Severe dehydration
Which laboratory test result indicates a high level of bilirubin type D?
Which laboratory test result indicates a high level of bilirubin type D?
- 0.4 MG/DL
- 16.3 H MG/DL (correct)
- 0.1 MG/DL
- 0.0-0.4 MG/DL
Which enzyme abbreviation indicates lactate dehydrogenase?
Which enzyme abbreviation indicates lactate dehydrogenase?
What is a potential consequence of enzyme induction in the body?
What is a potential consequence of enzyme induction in the body?
Increased levels of which enzyme may indicate damage to muscle tissue?
Increased levels of which enzyme may indicate damage to muscle tissue?
What does an elevation in gamma glutamyl transferase (GGT) levels suggest?
What does an elevation in gamma glutamyl transferase (GGT) levels suggest?
Which blood component level is typically monitored to assess kidney function?
Which blood component level is typically monitored to assess kidney function?
What happens to enzymes when cell membranes are damaged?
What happens to enzymes when cell membranes are damaged?
Which of the following statements about the presence of enzymes in blood is true?
Which of the following statements about the presence of enzymes in blood is true?
What is the primary fluid obtained for laboratory assays of enzyme activity?
What is the primary fluid obtained for laboratory assays of enzyme activity?
Why is serum preferred over plasma for some laboratory assays?
Why is serum preferred over plasma for some laboratory assays?
What contributes to basal levels of enzymes in a healthy individual?
What contributes to basal levels of enzymes in a healthy individual?
How is plasma different from serum in terms of preparation?
How is plasma different from serum in terms of preparation?
What is the primary role of most diagnostically important enzymes?
What is the primary role of most diagnostically important enzymes?
What process is used to obtain serum from a blood sample?
What process is used to obtain serum from a blood sample?
What percentage of normal, healthy individuals will typically have results within 1 standard deviation of the mean in a Gaussian distribution?
What percentage of normal, healthy individuals will typically have results within 1 standard deviation of the mean in a Gaussian distribution?
How is the reference range for cholesterol values typically established?
How is the reference range for cholesterol values typically established?
What constitutes impaired fasting glucose levels?
What constitutes impaired fasting glucose levels?
Which statement is true regarding isozymes?
Which statement is true regarding isozymes?
What is the critical difference in laboratory tests?
What is the critical difference in laboratory tests?
How do droppings of the top and bottom 2.5% affect skewed distributions?
How do droppings of the top and bottom 2.5% affect skewed distributions?
What is the mean cholesterol level typically observed in the American population?
What is the mean cholesterol level typically observed in the American population?
What percentage of normal, healthy individuals will typically have results within 3 standard deviations in a Gaussian distribution?
What percentage of normal, healthy individuals will typically have results within 3 standard deviations in a Gaussian distribution?
What does an elevated BUN level typically indicate?
What does an elevated BUN level typically indicate?
Which of the following is NOT part of a standard renal profile?
Which of the following is NOT part of a standard renal profile?
What organ is primarily assessed through the liver profile?
What organ is primarily assessed through the liver profile?
Which test is primarily used to monitor blood sugar levels?
Which test is primarily used to monitor blood sugar levels?
What does a low CO2 level suggest?
What does a low CO2 level suggest?
What determines the different proportions of isoenzymes in various tissues?
What determines the different proportions of isoenzymes in various tissues?
Which isozyme is denoted as HHHH?
Which isozyme is denoted as HHHH?
Which of the following tests is used to assess muscle damage?
Which of the following tests is used to assess muscle damage?
How many different isoenzymes of lactate dehydrogenase exist?
How many different isoenzymes of lactate dehydrogenase exist?
What is the abbreviation for alkaline phosphatase?
What is the abbreviation for alkaline phosphatase?
Which condition can elevated ALT levels indicate?
Which condition can elevated ALT levels indicate?
At what time does CK-MB peak in plasma after a myocardial infarction?
At what time does CK-MB peak in plasma after a myocardial infarction?
What might a high triglyceride level suggest?
What might a high triglyceride level suggest?
What type of structure is creatine kinase active as?
What type of structure is creatine kinase active as?
If an enzyme sample has a higher concentration, what will likely occur?
If an enzyme sample has a higher concentration, what will likely occur?
Which of the following is a common use for routine health exams?
Which of the following is a common use for routine health exams?
What does an increased level of sodium typically indicate?
What does an increased level of sodium typically indicate?
Which of the following proteins returns to normal levels in the shortest time after a myocardial infarction?
Which of the following proteins returns to normal levels in the shortest time after a myocardial infarction?
What happens to reaction formation if the amount of enzyme present is decreased?
What happens to reaction formation if the amount of enzyme present is decreased?
In which test would you primarily assess liver damage?
In which test would you primarily assess liver damage?
Which electrolyte is primarily responsible for maintaining fluid balance in the body?
Which electrolyte is primarily responsible for maintaining fluid balance in the body?
Which enzyme is a marker for liver tissue and muscle?
Which enzyme is a marker for liver tissue and muscle?
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Study Notes
Enzyme Activity Assays
- Most enzymes are not normally present in the blood.
- Damaged cell membranes release enzymes into surrounding fluids.
- Laboratory assays most often use serum, which is the fluid portion of blood after clotting.
- Basal enzyme levels are normally due to cell turnover.
- Elevated enzyme levels in the blood may be due to cell membrane injury, enzyme induction, tumor, or cell proliferation.
- In the chemistry profile, results for the normal, healthy population show a Gaussian distribution.
- 67% of normal, healthy individuals will give a result within 1 standard deviation of the mean.
- 95% of normal, healthy individuals will give a result within 2 standard deviations of the mean.
- 99.7% of normal, healthy individuals will give a result with 3 standard deviations of the mean.
- Most reference ranges are established using the mean + 2 standard deviations of the mean.
- If a distribution of test results of a normal, healthy sample group is not Gaussian but skewed, the top and bottom 2.5% are dropped to establish the reference limits for that test.
- Intraindividual and interindividual variation exist within lab test results, meaning individuals and populations can differ.
- The critical difference is the difference between serial test results that must occur before significance can be claimed.
- Isoenzymes are variant forms of the same enzyme that differ in their physical properties.
- Different isoenzymes can be present in different organisms, different tissues of the same organism, and different cells of the same tissue.
- Isoenzymes can be used to determine the source of enzyme elevation.
- Lactate dehydrogenase (LDH) has 5 different isoenzymes, each containing varying combinations of H and M subunits.
- The more enzyme present, the greater the reaction velocity.
- The assay compares the amount of product produced in a given time to standards of known enzyme concentrations.
- The amount of enzyme in the sample can then be determined.
###Â Clinical Significance
- Cardiac Profile
- Levels of cardiac markers such as creatinine kinase (CK), CK-MB, Troponin I and Troponin T are used to diagnose and monitor cardiac injury from myocardial infarction (heart attack).
- Myoglobin (MB) is the fastest-rising protein in the blood after a heart attack and returns to normal in the first 24-36 hours.
- CK-MB rises 6-10 hours after a heart attack, peaks about 18-24 hours, and returns to normal within 1-3 days.
- Troponin I and T elevate more slowly, peaking about 18-24 hours and remaining elevated for 5-9 days (Troponin I) or 14 days (Troponin T).
- Liver Profile
- Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are liver enzymes and are elevated in liver disease.
- Alkaline phosphatase (ALP) is elevated in liver disease and bone disorders.
- Gamma-glutamyltransferase (GGT) is often elevated in liver disease.
- LDH is elevated in liver and muscle disorders.
- Renal Profile
- Creatinine (CREAT) and blood urea nitrogen (BUN) are elevated in kidney disease.
- Muscle Profile
- Creatinine kinase (CPK) is elevated in muscle diseases.
- Lactate dehydrogenase (LDH) is elevated in muscle and liver disorders.
###Â Key Enzymes
- Creatine kinase (CK) is active as a dimer and has two types of subunits: B and M.
- BB (CK1)
- MB (CK2)
- MM (CK3)
- Lactate dehydrogenase (LDH) consists of four subunits of two different types: H and M.
- HHHH (LD1)
- HHHM (LD2)
- HHMM (LD3)
- HMMM (LD4)
- MMMM (LD5)
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