Blood tests can detect and diagnose a variety of diseases, especially routine blood tests, which are of great importance in the diagnosis of hematologic disorders. If a person’s blood test reveals an abnormally high number of white blood cells, with a predominance of monocytes, and if the patient has anemia and thrombocytopenia, the most common disease is acute monocytic leukemia, which can be further diagnosed by bone marrow aspiration. Other neoplastic diseases can also be diagnosed through blood tests, such as abnormally high concentrations of alpha-fetoprotein found through serological tests, which require a high degree of vigilance as to whether it is caused by liver cancer. If serological tests reveal an abnormally high concentration of carcinoembryonic antigen, it is important to be alert to the possibility of a malignant tumor of the digestive tract. Blood tests can detect a variety of diseases, and are especially important for the detection of various tumor diseases.