What are the advantages and disadvantages of the various biomarkers that can be used to diagnose patients with acute myocardial infarction?
Biomarker |
Advantages |
Disadvantages |
TnT, TnI |
Onset 2-3 hours, peak 24-36 hours, |
Elevated in non MI cases eg PE, myocarditis ie detects cardiac injury not cause Assay variability (TnI) for reference range Washout and peak altered by reperfusion May need second test if first value taken too early Modest correlation of size of MI with peak level Incomplete understanding of elevation after cardiac surgery and non cardiac surgery Baseline higher in chronic renal failure |
CK |
Widely used and available |
Non specific as present in skeletal muscle and brain |
CK MB |
Level and ratio improves specificity cf CK |
Less specific and sensitive than troponin |
Myoglobin |
Theoretically rapid detection |
Lacks specificity and no earlier detection than Tn |
AST |
Historically used with CK and LDH |
Non specific |
LDH |
Late onset and offset |
Present in many tissues. Requires isoenzymes |
CRP |
Marker of inflammation |
Non specific |
ESR |
Additive prognostic benefit esp women |
|
Novel biomarkers |
Copeptin, if levels low can rule out MI in addition to negative Troponin Heart-type Fatty Acid Binding Protein (H-FABP) is an early marker of ischaemia.
Other biomarkers of myocyte injury include glycogen phosphorylase BB (GP-BB), myeloperoxidase, pregnancy associated plasma protein A (PAPP-A) |
Raised Copeptin is not specific to cardiac disease.
Not shown to be superior to Troponin |
The paper was written for 2010.
Since then, none of these exciting "novel biomarkers" have become commonplace.
Furthermore, the older biomarkers which are non-specific (such as AST and CK) have not fallen off the list, even though we have known since the 1950s that they are essentially useless.
In the event that the above "model" answer table is too easy to memorise, I direct the reader to a lucid interpretation of the current state by Anthony McLean et al (2012). Alternatively, this 2006 article in Circulation covers cardiovascular biomarkers in excessive pedantic detail.
McLean, Anthony S., and Stephen J. Huang. "Cardiac biomarkers in the intensive care unit." Ann Intensive Care 2.8 (2012): 1-11.