¼
total volume in cuvette
ðÞmolar extinction coefficient of NADPH volume of serum used mlðÞ¼1 : 05
6 : 22 10 ^3 0 : 05
¼ 3376
Note If we use an antibody against CK-M, we get value of only CK-B from this
enzyme. So to get activity of CK-MB, multiply value 3376 with factor 2 (i.e.,
3376 2 ¼6752). If we follow the above process without CK-M antibody, then
value obtained will be for total CK activity. Calculation of CK-MB % is used to
predict the occurrence of myocardial infarction. CK-MB % is calculated as:
CK-MB%¼
CK-MB IU=L
TotalCKIU=L100
33.7 Clinical Significance...............................
Normal range of CK-MB activity is 24–195 IU/L in males and 24–170 IU/L in
females. The total CK activity range is 60–400 U/L in males and 40–150 U/L in
females. The increase in CK activity is mainly caused by skeletal muscle disease,
i.e., muscular dystrophy, myocardial infarction, and cerebrovascular damages. Other
factors like polymyositis, viral myositis, and hypothyroidism also increase CK
levels. The increase in the CK activity (particularly CK 2 or MB isoenzyme) is
observed within 6–8 h after onset of myocardial infarction. The activity reaches to
maximum levels after 12–24 h and comes to normal after 3–4 days. Increase in levels
of both total CK activity and CK-MB activity can be observed in the serum of
patients suffering myocardial infarction or after physical exercise. The increase is not
observed in heart failure and coronary insufficiency. The CK-MB % less than 5.5%
indicates probability of no myocardial infarction or myocardial infarction occurred
in less than 4–6 h prior to sample collection. The CK-MB % between 5.5 and 20%
indicates most probable cause of myocardial infarction or myocardial damage due to
cardiac catheterization.
33.7 Clinical Significance 133