What color tube is primarily used for serum tests?

The red top tube is primarily used for serum tests because it contains no additives that would interfere with the coagulation process. This tube allows the blood to clot, after which the serum can be separated from the clotted blood by centrifugation. The absence of any anticoagulants in the red top tube means that the serum collected is suitable for a variety of tests that require serum, such as certain biochemical analyses and serological tests.

Other tubes, such as the blue top tube, are used for coagulation studies and contain sodium citrate as an additive, which is not suitable for serum testing. The purple top tube contains EDTA, an anticoagulant that preserves blood cells but is inappropriate for tests requiring serum. The green top tube typically contains heparin, which prevents clotting and is also not designed for serum tests. Thus, the red top tube is the correct choice for collecting serum samples.