Post on 29-Jan-2016
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Enzymes, Cardiac Markers, Hepatic Tests
• clinically useful enzymes: tissue sources
• preanalytical variables affecting enzyme activities
• isoenzymes
• myocardial markers and diagnosis of myocardial injury
• hepatic function, choice of tests, interpretation of results
Clinically Useful Enzymes
• LDH: heart, liver, muscle, RBC, neural tissue, leukocytes, tumor cells
• AST: liver, heart, muscle
• ALT: liver
• CK: muscle, heart, neural tissue
• ALP: liver, bone, intestine, placenta
• GGT: liver, pancreas, kidney
Preanalytical Variables
• IN THE PATIENT- age, sex, food, exercise, trauma
• IN THE SAMPLE
• Hemolysis -inc in Total LDH & LDH 1/II
• EDTA: inhibition of ALP
CK Isoenzymes
• Dimer: M & B monomers
• CK- 1: BB; neural & mesenchymal tissue
• CK- 2: MB; muscle (<1%); heart (<40%)
• CK- 3: MM; heart (60 - 80%) muscle (>99%)
CK Isoforms
• CKMM-3 & CKMB-2 (tissue isoforms of CK) after tissue release are converted by carboxypeptidases in blood to:
- CKMM-2 & CKMM-1, and- CKMB-1
Detection of Myocardial Injury Major Issues
• THE Acute Coronary Syndrome - stable angina- unstable angina- acute myocardial infarction
• Choice of biochemical cardiac marker
Acute Coronary Syndrome: Risk Stratification
• Chest pain
• ECG – ST segment changes
• Troponins
• Other risk factors: CRP, fibrinogen, BNP
Myocardial Markers
• Troponin-I or T
• Myoglobin
• CK- MB
• CK- MB Relative Index
• CK Isoforms
Myocardial Markers
Marker Time to (hr) Length of CK-MB 3-12 48- 72 hr Tn-I 3-12 5 - 10d Tn-T 3-12 5 - 14d Myoglobin 1-4 18 - 24hr CK-isoforms 1-4 1 - 4d
Myocardial Markers:References
• Donnelly, R, Millar-Craig, MW: Cardiac troponins: IT upgrade for the heart. Lancet 1998;351:537-9
• Apple,FS & Wu,A: Myocardial infarction redefined: role of cardiac troponin testing. Clin Chem 2001; 47:377-8
• Sabatine, MS et al: Multimarker approach to risk stratification in non-ST elevation ACS. Circulation 2002; 105:1760-3