CYGB and chronic obstructive pulmonary disease: The mean corpuscular hemoglobin concentration, which is an index that reflects the average volume of RBCs, is recognized as an indicator of the average HGB concentration per RBC and is predictive of the development of a variety of diseases, including chronic obstructive pulmonary disease (COPD), internal carotid artery stenosis, and hepatocellular carcinoma (HCC) metastasis (29–31).