Which of the following biochemical test is used to diagnose Dubin Johnson syndrome?

Bromsulphalein test (BSP) is the diagnostic test for Dubin-Johnson Syndrome. Biliary excretion of numerous anionic compounds such as Bromsulphalein (BSP) is compromised in Dubin-Johnson Syndrome (DJS). In this test, BSP is administered as IV bolus and its clearance from plasma is determined. BSP levels show a characteristic rise in patients with DJS after 90 minutes of injection, due to reflux of conjugated BSP into the circulation from the hepatocyte. Ref: Davidson's principles and practice of Medicine, 20th Edition, Chapter 23, Page 945; Harrison's Principles of Internal Medicine, 16th Edition, Page 1821; Digestive Diseases and Sciences Vol/17 numbers 6.