There are two parts of platelet examination: the first part is the examination of platelet count. The examination of platelet count includes whether the number of platelets in peripheral blood is within the normal range, whether the number of platelets is increasing or decreasing, and also the examination of platelet pressure volume and platelet volume distribution width. The functional examination of platelets, including platelet contraction test, as well as the examination of platelet-related immunoglobulin and platelet aggregation test, etc. Through these tests, a clear diagnosis of platelet count and function and status can be made. For example, the most common disease in patients with severely reduced platelet count is immune thrombocytopenic purpura. The second part is the examination of platelet function. If this patient has a normal platelet count, but the bleeding time is significantly prolonged, and the platelet aggregation function is found to be significantly decreased by the examination, the greatest possibility is platelet anemia.