Myoglobin is used infrequently as a cardiac biomarker. Its historic use was as an early-onset marker since it is elevated first, before CK-MB and troponin. Myoglobin is an oxygen-binding protein in cardiac and skeletal muscle. It is released earlier after muscle injury than cardiac troponins and CK-MB and returns to normal faster than either of these other markers. It rises within 2-4 hours after chest pain, peaks in 6-12 hours, and is usually normal within 24-36 hours.
Myoglobin is in all muscle, not just cardiac muscle. It is the reason muscle is red in color. Thus, it is a very nonspecific marker for cardiac damage. It can be elevated after exercise and in many clinical scenarios. For these reasons, myoglobin is rarely measured. Many laboratories no longer offer myoglobin testing and emergency room physicians are no longer routinely trained in its use. As troponin assays have become more sensitive they have replaced myoglobin assays.
Myoglobin reference ranges for adults when an immunoassay method is used are approximately:
- Male 17-106 ng/mL
- Female 1-66 ng/mL