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
💬 Troponin I remains elevated for 7–10 days post-MI, longer than CK-MB (2–3 days) or Myoglobin (24 hours).

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
💬 CK-MB is present in both cardiac and skeletal muscle, reducing its specificity. Troponins are highly cardiac-specific.

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
💬 CK-MB levels fall within 2–3 days, so a new rise suggests reinfarction. Troponin stays elevated longer and is less useful for that purpose.

4. Troponin elevation in absence of MI is NOT typically caused by:

  • A. Sepsis
  • B. Renal failure
  • C. Pulmonary embolism
  • D. Mild asthma
💬 Troponin can be elevated in critically ill patients or other cardiac stressors. Mild asthma typically does not affect troponin levels.

5. The earliest marker to rise after myocardial infarction is:

  • A. CK-MB
  • B. Troponin
  • C. Myoglobin
  • D. LDH
💬 Myoglobin rises as early as 1–2 hours after MI but lacks specificity. Troponin and CK-MB rise later.

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
💬 CK-MB levels fall quickly after infarction, so a second rise can signal reinfarction.

7. In chronic kidney disease (CKD), which biomarker is more reliable?

  • A. Troponin I
  • B. CK-MB
  • C. LDH
  • D. Myoglobin
💬 Troponin can be elevated in CKD without MI. CK-MB is less affected by renal dysfunction, making it more specific in CKD.

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
💬 Troponin T exists in both cardiac and skeletal muscle forms, but assays are cardiac-specific. Troponin I is more exclusively cardiac.

9. Which marker is most likely to normalize within 48 hours post-MI?

  • A. Troponin I
  • B. LDH
  • C. CK-MB
  • D. Troponin T
💬 CK-MB typically returns to baseline within 48–72 hours, unlike troponins which stay elevated longer.

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
💬 The “second window” refers to a re-rise in CK-MB levels after reinfarction, useful in serial measurement.

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
💬 Using both Troponin and CK-MB combines early sensitivity (CK-MB) and prolonged specificity (Troponin).

12. High-sensitivity troponin assays:

  • A. Allow earlier MI detection
  • B. Are obsolete
  • C. Are slower than CK-MB
  • D. Have poor sensitivity
💬 High-sensitivity assays detect smaller myocardial injury earlier than standard troponin or CK-MB tests.

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
💬 The magnitude of troponin elevation reflects the infarct size and has prognostic significance.

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
💬 In elderly or CKD patients, baseline troponin may be mildly elevated without acute MI. CK-MB is usually normal in such cases.

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
💬 Troponins are highly specific to cardiac tissue, making them more reliable than CK-MB, which may be elevated in muscle injury.

16. When does CK-MB typically peak after infarction?

  • A. 1 hour
  • B. 18–24 hours
  • C. 48–72 hours
  • D. 5 days
💬 CK-MB typically peaks between 18 to 24 hours after the onset of MI symptoms.

17. Which condition can cause false elevation of CK-MB?

  • A. Hyperlipidemia
  • B. Hypoglycemia
  • C. Skeletal muscle injury
  • D. Hypertension
💬 CK-MB can be released from damaged skeletal muscle, leading to false-positive interpretations in trauma or myopathies.

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
💬 Serial troponin at 0 and 3 or 6 hours is standard for ruling out MI depending on institutional protocols.

19. CK-MB elevation more than troponin suggests:

  • A. Myocarditis
  • B. Skeletal muscle injury
  • C. Renal failure
  • D. Pericarditis
💬 If CK-MB is elevated more than troponin, consider muscle injury outside of the heart.

20. Troponin levels may be falsely elevated due to:

  • A. Heterophile antibodies
  • B. Hemoglobin variants
  • C. Diabetes
  • D. Hematuria
💬 Heterophile antibodies can interfere with immunoassays, causing false-positive troponin results.

Troponin vs CK-MB: 20 Key Differences
# Feature Troponin (I/T) CK-MB
1Specificity to heartVery high (cardiac-specific)Moderate (also in skeletal muscle)
2SensitivityHighModerate
3Time to rise after MI3–6 hours3–12 hours
4Time to peak12–24 hours18–24 hours
5Duration of elevation7–14 days2–3 days
6Use in reinfarctionNot usefulUseful (short half-life)
7Detection in renal failureMay remain chronically elevatedMore reliable
8Assay typesHigh-sensitivity availableStandard immunoassays
9CostGenerally higherLower
10False positivesPossible with heterophile antibodiesMuscle injury, hypothyroid states
11Prognostic valueStrong predictor of mortalityLimited
12Presence in skeletal muscleNoYes (to some extent)
13Clinical rolePrimary diagnostic tool for MIAdjunct, used for reinfarction
14Reference range unitsng/mLng/mL or IU/L
15Effect of ageMay increase in elderlyLess age-dependent
16Effect of strenuous exerciseMinimalMay falsely elevate
17Interpretation complexityClear-cut with serial testingMay need baseline comparisons
18Use in non-MI conditionsElevated in PE, sepsis, CHFElevated in trauma, myopathy
19Cardiac isoforms measuredTroponin I or TCK-MB isoenzyme
20Widely used in current guidelinesYes (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. 

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