What is the primary use of the gray top tube?

The gray top tube is primarily used for glucose and lactic acid testing due to its unique additive properties. It typically contains sodium fluoride, which acts as a glycolytic inhibitor, preventing the breakdown of glucose in the sample for a period of time. This allows for accurate measurement of glucose levels, particularly in situations where there might be a delay in processing the sample. Additionally, the presence of potassium oxalate in some gray top tubes helps to prevent clotting, which is essential for accurate lactic acid measurement as well.

While blood gas analysis is performed using a different type of tube specifically designed for that purpose, hematology tests typically require tubes with EDTA as an additive, and serum tests need tubes that allow for clotting without the influence of fluoride. Therefore, the primary and best-suited purpose for the gray top tube remains its use in glucose and lactic acid testing.