Which test requires the specimen to be collected in a gray top tube?

The correct choice is related to glucose testing, which is commonly performed using a gray top tube. The gray top tube contains a preservative, typically sodium fluoride, which inhibits glycolysis, the breakdown of glucose by cells. This property is crucial when collecting blood samples for glucose testing because it ensures that the glucose levels measured in the laboratory remain stable and accurately reflect the patient's blood glucose levels at the time of collection.

In contrast, the other tests listed do not typically require a gray top tube:

• A complete blood count (CBC) generally requires a lavender top tube, which contains EDTA as an anticoagulant.

• A lipid panel is usually performed using a serum separator tube, typically a red or gold top tube, to allow for the separation of serum from the blood cells.

• Electrolyte testing can be done using various types of tubes, including green top tubes that contain heparin or serum separator tubes, but not specifically a gray top tube.

Thus, the requirement of the gray top tube for glucose testing is significant in ensuring that accurate results are obtained in clinical settings.