Answer: Relative index is a ratio of CK-MB/total CK. The formula is
Relative index = CK-MB/total CK x 100
Relative index helps in differentiating elevation of CK-MB between skeletal and cardiac origin.
- Ratio < 3 is consistent with skeletal muscle source
- Ratio > 5 indicates cardiac source
TP Singh, AK Nigam, AK Gupta, B Singh. Cardiac Biomarkers: When to Test? – Physician Perspective Journal, Indian Academy of Clinical Medicine z Vol. 12, No. 2, April-June, 2011