The causes of high cytokeratin 19 fragment 3.8 may be lung cancer, other tumor diseases, liver diseases, renal failure and so on. The normal serum cytokeratin 19 fragment should be less than 3.30ng/ml. when epithelial cells become cancerous, a large number of cells are destroyed, which produces a large number of cytokeratin 19 fragments, leading to elevated values of cytokeratin 19 fragments, and the common reasons for its elevation are as follows: 1. Cytokeratin 19 fragment is the preferred marker for non-small cell lung cancer, with a sensitivity of 80%, which is both early diagnosis and related to the growth of the mass, and is an important indicator for follow-up, observation of the efficacy of treatment and judgment of the prognosis. 2. Other tumor diseases: for example, bladder cancer, pancreatic cancer, gallbladder cancer, cervical cancer, colon cancer, gastric cancer, cytokeratin 19 fragment will also be increased. However, it is generally not elevated in diseases other than tumors. 3. CYFRA21-1 levels are also slightly elevated in individual benign liver diseases, renal failure, and pneumonia. Therefore, the cytokeratin 19 fragment value of 3.8 alone cannot accurately determine the cause, and it is recommended to go to a regular hospital in time to complete the relevant examinations and identify the cause.