<prompt> Answer this question truthfullyWhat laboratory tests are used to diagnose deep vein thrombosis?  <response>: <reason> D-dimer is used in the diagnosis of deep vein thrombosis among patients with low or unlikely probability of venous thromboembolism. While 500 ngmL has long been the most commonly used cut off value for abnormal D-dimer concentration, recent studies suggest the use of an age adjusted cut-off concentration of D-dimer. The age adjusted cut-off value of D-dimer is 500 ngmL for subjects whose age is less than 50 years, and the age multiplied by 10 for subjects older than 50 years. 