For what specific purpose is sodium heparin in the light brown tube top used?

Sodium heparin, which is found in the light brown tube top, is specifically used for the determination of serum lead levels. The anticoagulant properties of sodium heparin prevent the blood from clotting, allowing for accurate analysis of lead levels in the serum. Lead testing typically requires a sample that has not clotted, as clotted samples can lead to inaccurate results due to cellular contamination.

This tube is particularly beneficial for tests that demand a plasma sample, as sodium heparin does not interfere with the analysis of lead, while offering a stable and reliable environment for measuring other important serum components.

In contrast, other purposes listed, like microbiology or immunohematology, would typically utilize different types of collection tubes designed for those specific analyses. For example, microbiology often requires culture media, while immunohematology may favor EDTA tubes to preserve cellular integrity.