In what situation would you use a gray top tube?

The gray top tube is specifically used for glucose and lactic acid testing due to its unique additive, sodium fluoride, which acts as a glycolytic inhibitor. This means that it prevents the metabolism of glucose by any cells that might be present in the sample, which is crucial for accurate glucose measurement. Additionally, the gray top tube often contains potassium oxalate, which acts as an anticoagulant, further supporting the integrity of the glucose and lactic acid levels in the sample.

In contrast, testing for heavy metals typically requires a different type of tube that is designed to minimize contamination and is often a royal blue top tube. Hematology analysis usually involves lavender top tubes containing EDTA, which is suitable for binding calcium and preserving blood cell morphology for examination. Serum electrophoresis is performed using serum separator tubes, often with a gold or red top, to separate serum from cells. Thus, the gray top tube's design specifically aligns with the needs of glucose and lactic acid testing, making it the correct choice in this context.