Evaluation of creatine kinase (CK)-MB to total CK ratio as a diagnostic biomarker for primary tumors and metastasis screening.

Objective: Creatine kinase (CK) and its myocardial band isoenzyme (CK-MB) were considered important diagnostic indicators for identifying suspected acute myocardial infarction. However, the serum level of CK-MB is frequently exaggerated in some pathological states without cardiogenic damage, like cancer. Sometimes, the CK-MB level is even greater than the total CK. This study intended to investigate the association between malignancy and an abnormally high ratio of CK-MB to total CK (CK-MB/CK) and to assess the diagnostic relevance of this ratio as a biomarker for cancer. Methods: Patients hospitalized between September 2019 and September 2022 at Shandong Provincial Qianfoshan Hospital (Jinan, Shandong, China) with serum CK-MB activity greater than total CK activity (CK-MB/CK > 1.0) were recruited as research subjects. Then the demographic and clinical characteristics of these patients were systemically analyzed. The correlation between clinical characteristics (such as cancer types, tumor locations, and tumor metastasis) and laboratory test results (such as serum CK-MB activity, total CK activity, and the CK-MB/CK ratio) was also investigated. Results: We found that over 44% of the patients with CK-MB/CK > 1.0 were diagnosed with malignancies, and the CK-MB/CK ratio in malignancies patients was significantly higher than in non-malignancies patients. The increase of CK-MB/CK ratio was most obvious in patients with colorectal carcinoma and prostatic carcinoma. Additionally, extremely elevated CK-MB/CK ratios were observed in individuals with metastatic neoplasms, especially in those who suffered from numerous sites of metastasis. Conclusions: The serum CK-MB/CK ratio can be utilized as a readily accessible supplement diagnostic biomarker in screening for primary and metastatic cancers.