Mb clinical test significance and reference values

Reference range: Radioimmunoassay (RIA) method: 6 ~ 80 μg/L.

Influencing factors:

1. Serum myoglobin fluctuates throughout the day, with the highest value at 9:00 a.m. and the lowest value between 6:00 p.m. and 12:00 p.m. Samples should be collected regularly during continuous testing.

2. Prevent hemolysis of specimens.

3． Radioactive drugs can affect test results.

Clinical significance:

1.Mb is an oxygen-binding protein that is widely found in skeletal muscle, cardiac muscle, and smooth muscle, accounting for about 2% of all proteins in muscle. Mb has a small molecular weight, only 17.8kD, which is smaller than CK-MB (84kD) and even smaller than lactate dehydrogenase (134kD), and is located in the cytoplasm. From a pathophysiological perspective, the sooner or later the appearance of cardiac markers depends on the size of the molecule and its presence in the cell. Depends on the location. The smaller the molecular weight of the marker, the easier it is to penetrate the intercellular space into the blood. High-concentration substances in the cytoplasm appear in the blood earlier than substances and structural proteins in the nucleus or mitochondria. Therefore, Mb appears earlier when myocardial injury occurs. So far, myoglobin is the earliest measurable myocardial injury marker after acute myocardial infarction (AMI).

2. When AMI patients have an attack, Mb in the cytoplasm is released into the blood, which rises in 2 hours, reaches a peak at 6 to 9 hours, and returns to normal levels in 24 to 36 hours. The negative predictive value of Mb is 100%. Within 2 to 12 hours after the onset of chest pain, acute myocardial infarction can be ruled out if Mb is negative. Mb combined with electrocardiogram can improve the efficiency of early diagnosis of acute myocardial infarction. Improved from 62% using ECG alone to 82%. In patients with successful thrombolytic treatment, the Mb concentration can decrease significantly 2 hours after thrombolysis.

3． Clinically, in addition to acute myocardial infarction, serum Mb will increase during thoracotomy, excessive physical exercise, skeletal muscle trauma, progressive muscle atrophy, shock, severe renal failure, and intramuscular injection. Therefore, the main problem in the clinical application of Mb is the specificity. The accuracy is not high, ranging from 60% to 95%. Especially when the early electrocardiogram and other markers have not changed, there are certain risks in deciding whether to use thrombolytic therapy based on Mb alone.