Collection Instructions
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Container/Tube: Gold-top tube(s)
Specimen: 2 mL serum ( 1.5 mL min)
Transport Temperature: Frozen serum in plastic vial.
Patient Preparation
CK is most commonly elevated in acute myocardial infarction (AMI) in which it has its greatest usefulness. Collection of specimen at onset of symptoms to establish baseline values is needed. A patient at onset of AMI will have normal results, but some patients reach medical attention at or beyond CK peak. To support the diagnosis of AMI, three CK isoenzyme determinations have classically been recommended, one on admission, a second 12 hours after admission, a third 24 hours after admission. Another at 48 hours may be needed. CK-MB usually peaks between 15 and 20 hours after the onset of a myocardial infarction. Pappas summarizes current literature regarding timing as follows. In non-Q wave, incomplete occlusion, nontransmural MI, CK-MB peaks on the average 15 hours from onset. In Q wave (complete occlusion) (transmural) infarction, CK-MB average peak is 17 to 20 hours after onset of symptoms. He emphasizes the importance of a sample for CK-MB drawn 16 hours after onset.1 When increased CK-MB values have returned to normal, CK isoenzyme determinations are usually no longer required.
Causes for Rejection Moderate or excessive hemolysis
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Methodology
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Total: kinetic
Isoenzymes: agarose gel electrophoresis with densitometry
Test Includes
Total CK and relative percentage of BB (CK-1), MB (CK-2), and MM (CK-3); percentage of macro CK, if present
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Days Performed
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TAT: 4 to 7 Days
Three fractions normally may be found, each an isoenzyme:
• MM is found in normal serum.
• MB is the myocardial fraction associated with MI and occurs in certain other states. MB can be used in estimation of infarct size.
MB increases have been reported with entities that cause damage to the myocardium, such as myocarditis, some instances of cardiomyopathy, and with extensive rhabdomyolysis, Duchenne muscular dystrophy, malignant hyperthermia, polymyositis, dermatomyositis, mixed connective tissue disease, myoglobinemia, Rocky Mountain spotted fever, Reye syndrome, and rarely in rheumatoid arthritis with high titer RF. CK-MB does not generally abruptly rise and fall in such nonacute MI settings, as it does in acute myocardial infarct (AMI).
• BB is rarely present. BB has been described as a marker for adenocarcinoma of the prostate, breast, ovary, colon, adenocarcinomas of gastrointestinal tract, and for small cell anaplastic carcinoma of lung. BB has been reported with severe shock and/or hypothermia, infarction of bowel, brain injury, stroke, as a genetic marker in some families with malignant pyrexia, and with MB in alcoholic myopathy.
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