-Citrated Blue Top Tube (BTT) must be drawn to the fill line.
-Completely invert tube three or four times to mix. Do Not Shake.
-Centrifuge tube at 3000 rpm for 10 minutes or Stat Spin for 3 minutes at 8500 rpm with the brake OFF as soon
as possible after collection.
-If testing cannot be performed within specimen stability transfer plasma (avoiding platelet contamination) to
polypropylene tube with plastic pipette for storage within two hours of collection.
-If sending to another testing location: If combined with other coag testing send only one frozen,
plasma aliquot (1mL) for all tests, with specimen label. Also send original Blue Top Tube (BTT) in case sample needs to be checked for clot.
An elevation of D-dimer (>500 ng/mL) indicates activation of coagulation with formation and degradation of cross-linked fibrin. It is a very sensitive, albeit very nonspecific, marker of pulmonary embolism (PE) or deep venous thrombosis (DVT). The main value of D-dimer testing in the setting of possible PE or DVT is its negative rule-out capability. A negative D-dimer result, when the pre-test probability of PE or DVT is low to intermediate, essentially excludes PE and DVT. In healthy adults D-dimer levels increase in a linear fashion after age 50. Based on current literature**, by optimizing the cutoffs with age, the very high sensitivity of the test can be maintained while providing greater specificity. This allows a greater percentage of older adults to be ruled-out. This allows a simple calculation of AGE x 10 for patients over 50 years old. For example, a 65 year-old patient would now have a cutoff of < 650 ng/mL (i.e. values of 650 ng/mL or less considered negative).
**Righini M, Van Es J, Exter D, et al. Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism The ADJUST-PE Study. JAMA. 2014;311:1117.
**Raja AS, Greenberg JO, Qaseem A. Evaluation of Patients With Suspected Acute Pulmonary Embolism: Best Practice Advice From the Clinical Guidelines Committee of the American College of Physicians. Ann Intern Med. 2015;163:701.