What is the primary function of sodium citrate in laboratory settings?

Sodium citrate serves a critical role in laboratory settings primarily as an anticoagulant. Its main function is to prevent blood clotting during various laboratory tests by binding calcium ions in the blood. Calcium is an essential factor in the coagulation cascade; thus, by sequestering it, sodium citrate effectively interrupts the clotting process, allowing for more accurate analysis of blood components.

This characteristic makes sodium citrate particularly important when performing tests that require plasma, such as prothrombin time (PT) or activated partial thromboplastin time (aPTT), as it preserves the sample in a liquid state. This ability to maintain the integrity of samples ensures that the results are reliable and reflect the true state of the patient's blood composition at the time of testing.

In contrast to the other options, sodium citrate does not initiate coagulation, measure blood viscosity, or enhance clot formation. These functions are unrelated to the properties and applications of sodium citrate in laboratory practice. Understanding this component's action and its role in various tests is essential for accurate laboratory work and patient diagnosis.