D-dimer and thromboembolism – Cardiology MCQ

True regarding D-dimer assay in venous thromboembolism:
a) Positive D-dimer assay has a high positive predictive value
b) Negative D-dimer assay has a high negative predictive value
c) ELISA derived assays have poor diagnostic sensitivity
d) None of the above
Correct answer: b) Negative D-dimer assay has a high negative predictive value
A negative D-dimer is useful in excluding venous thromboembolism. Studies have shown that three month thromboembolic risk is less than one percent in those left untreated due to a negative test. But a positive D-dimer assay is not useful in diagnosis as many conditions like bleeding, trauma, surgery and cancer can cause elevated D-dimer values. ELISA derived assays have a diagnostic sensitivity of ninety five percent or more.