Ruling out acute deep vein thrombosis by ELISA plasma D-dimer assay versus ultrasound in inpatients more than 70 years old

In geriatric care, deep-vein thrombosis (DVT) is mostly diagnosed by noninvasive techniques. The objectives of this prospective study were: (1) to evaluate the power of ELISA plasma D-dimer assay versus ultrasound (US) in ruling out acute DVT of the lower limbs in symptomatic geriatric inpatients, and (2) to determine the most effective D-dimer cutoff value over the age of 70 years. Over a 10-month period, inpatients with suspected lower limb DVT simultaneously underwent US examination and ELISA plasma D-dimer assay. Noninclusion criteria were comorbid conditions able to modify the D-dimer level. Data were processed by receiver operating characteristic (ROC) curve analysis. In total, 150 patients (125 women, 25 men), average age 86.3 years (range 70-101) were included. A diagnosis of lower limb DVT was established in 53 patients (35.3%). With a 500 ng/mL D-dimer cutoff conventional value, DVT was ruled out in only five patients (3.3%), whereas a 750 ng/mL value ruled out DVT in 19 patients (12.7%) with a sensitivity of 98.1%, and a negative predictive value of 95.0%. The only false negative corresponded to a patient with a 15-mm thrombus in the distal calf. In inpatients above 70, an ELISA plasma D-dimer value smaller than 750 ng/mL is a rapid reliable noninvasive means to rule out lower limb DVT, if color flow Doppler ultrasound is not available on site.