Creatine Kinase MB
Creatine Kinase MB
1. Which biomarker remains elevated the longest after a myocardial infarction?
- A. CK-MB
- B. Myoglobin
- C. Troponin I
- D. LDH
2. Troponin is more specific than CK-MB because:
- A. CK-MB rises earlier
- B. CK-MB is also found in skeletal muscle
- C. Troponin is less sensitive
- D. Troponin is rapidly cleared
3. Which of the following is TRUE regarding CK-MB in MI diagnosis?
- A. It is more specific than troponin
- B. Useful for detecting reinfarction
- C. Peaks later than troponin
- D. Remains elevated for over a week
4. Troponin elevation in absence of MI is NOT typically caused by:
- A. Sepsis
- B. Renal failure
- C. Pulmonary embolism
- D. Mild asthma
5. The earliest marker to rise after myocardial infarction is:
- A. CK-MB
- B. Troponin
- C. Myoglobin
- D. LDH
6. CK-MB is most useful in which of the following clinical scenarios?
- A. Diagnosing non-cardiac chest pain
- B. Diagnosing reinfarction within days of initial MI
- C. Detecting chronic stable angina
- D. Screening in asymptomatic individuals
7. In chronic kidney disease (CKD), which biomarker is more reliable?
- A. Troponin I
- B. CK-MB
- C. LDH
- D. Myoglobin
8. Troponin T is produced by:
- A. Only cardiac muscle
- B. Both cardiac and skeletal muscle
- C. Smooth muscle only
- D. All muscle types equally
9. Which marker is most likely to normalize within 48 hours post-MI?
- A. Troponin I
- B. LDH
- C. CK-MB
- D. Troponin T
10. The “second window” phenomenon of CK-MB refers to:
- A. False-positive in elderly
- B. Re-elevation after reinfarction
- C. Diurnal variation
- D. CK-MB in stroke
11. Which combination offers the best sensitivity and specificity for MI?
- A. LDH and Myoglobin
- B. Troponin and CK-MB
- C. Troponin and LDH
- D. Myoglobin and CK-MB
12. High-sensitivity troponin assays:
- A. Allow earlier MI detection
- B. Are obsolete
- C. Are slower than CK-MB
- D. Have poor sensitivity
13. Troponin elevation correlates best with:
- A. Time since onset of chest pain
- B. Size of myocardial infarction
- C. Heart rate
- D. CK-MB values
14. A 75-year-old with chest pain has mildly elevated troponin and normal CK-MB. Most likely diagnosis:
- A. Acute STEMI
- B. Chronic troponin elevation (e.g., CHF or CKD)
- C. Acute pericarditis
- D. Acute massive PE
15. Which statement is TRUE?
- A. CK-MB is superior to troponin in all cases
- B. Troponin is more cardiac-specific than CK-MB
- C. CK-MB is not found in skeletal muscle
- D. Troponin is cleared faster
16. When does CK-MB typically peak after infarction?
- A. 1 hour
- B. 18–24 hours
- C. 48–72 hours
- D. 5 days
17. Which condition can cause false elevation of CK-MB?
- A. Hyperlipidemia
- B. Hypoglycemia
- C. Skeletal muscle injury
- D. Hypertension
18. For ruling out MI, serial troponin testing is performed at:
- A. 0 and 1 hour
- B. Only at presentation
- C. 0 and 3 or 6 hours
- D. 12 and 24 hours
19. CK-MB elevation more than troponin suggests:
- A. Myocarditis
- B. Skeletal muscle injury
- C. Renal failure
- D. Pericarditis
20. Troponin levels may be falsely elevated due to:
- A. Heterophile antibodies
- B. Hemoglobin variants
- C. Diabetes
- D. Hematuria
# | Feature | Troponin (I/T) | CK-MB |
---|---|---|---|
1 | Specificity to heart | Very high (cardiac-specific) | Moderate (also in skeletal muscle) |
2 | Sensitivity | High | Moderate |
3 | Time to rise after MI | 3–6 hours | 3–12 hours |
4 | Time to peak | 12–24 hours | 18–24 hours |
5 | Duration of elevation | 7–14 days | 2–3 days |
6 | Use in reinfarction | Not useful | Useful (short half-life) |
7 | Detection in renal failure | May remain chronically elevated | More reliable |
8 | Assay types | High-sensitivity available | Standard immunoassays |
9 | Cost | Generally higher | Lower |
10 | False positives | Possible with heterophile antibodies | Muscle injury, hypothyroid states |
11 | Prognostic value | Strong predictor of mortality | Limited |
12 | Presence in skeletal muscle | No | Yes (to some extent) |
13 | Clinical role | Primary diagnostic tool for MI | Adjunct, used for reinfarction |
14 | Reference range units | ng/mL | ng/mL or IU/L |
15 | Effect of age | May increase in elderly | Less age-dependent |
16 | Effect of strenuous exercise | Minimal | May falsely elevate |
17 | Interpretation complexity | Clear-cut with serial testing | May need baseline comparisons |
18 | Use in non-MI conditions | Elevated in PE, sepsis, CHF | Elevated in trauma, myopathy |
19 | Cardiac isoforms measured | Troponin I or T | CK-MB isoenzyme |
20 | Widely used in current guidelines | Yes (Class I recommendation) | Limited role |
CK-MB levels and interpretation
- Normal CK-MB levels are typically low or undetectable, usually 0-5 ng/mL or less than 5% of total CK levels.
- Elevated CK-MB levels are generally associated with heart muscle damage, such as during a heart attack or myocarditis.
- CK-MB levels can rise within 3-6 hours after a heart attack, peak around 12-24 hours, and return to normal within 48-72 hours.
- Elevations can also be caused by strenuous exercise, certain medications (like statins), muscle injuries, and other conditions.