The middle or ring fingers are the recommended sites for capillary puncture in adults. The index finger should not be used because of its increased sensitivity and more frequent use. The tip of the finger should not be used due to the short distance between the skin surface and bone; instead, the puncture should be made at the thickest part of the distal phalanx. The big toe is not recommended as a site for capillary collection, though it may be used in some cases.

The platelet function test is used to determine a patients response to aspirin therapy or other antiplatelet therapies. This test is also used to assess a patient's response to medications before cardiac catheterization or surgery. Platelet function tests can help clinicians assess and predict the risk of bleeding and of thrombosis associated with platelet dysfunction before, during, and after the procedures.

Blood type is determined by the presence or absence of antigens on the red blood cells (RBCs). If a person's blood is type A. there are A antigens on the RBCs, and the plasma agglutinin (antibody) that is present in the person's blood is anti-B. Type B blood has B antigens on the RBCs and anti-A agglutinins in the plasma. Type O blood has no antigens on the RBCs but both anti-A and anti-B agglutinins in the plasma. Individuals with type O blood, specifically O-negative blood, are considered universal donors due to their lack of antigens, making the blood less likely to be rejected or result in a transfusion reaction.

When collecting a blood specimen for trace elements, such as zinc, selenium, or mercury, the appropriate tube type is metal-free. These are specialty tubes designed so that they do not contaminate the sample with trace elements (including, but not limited to, metals) that are typically found in glass and plastic containers. These tubes usually have royal-blue tops and are available with EDTA or heparin, or they are free of additives. Samples for lead testing are collected in tan- topped tubes containing K2 EDTA.