Sulfobromophthalein sodium salt hydrate is primarily used in medical diagnostics as a liver function test agent. It is administered intravenously to assess the liver's ability to remove substances from the blood. After injection, the compound is taken up by liver cells and excreted into the bile. The rate at which it is cleared from the bloodstream provides valuable information about liver health and function. This test is particularly useful in detecting liver diseases, such as cirrhosis or hepatitis, and in monitoring the progression of these conditions. Additionally, it can help evaluate the liver's functional capacity before surgery or other medical interventions.