Does an immunochromatographic D-dimer exclude acute lower limb deep venous thrombosis?
BACKGROUND
A pre-test probability score and D-dimer may reduce the need for ultrasound examinations for excluding lower limb deep venous thrombosis (DVT).


OBJECTIVE
To establish the accuracy of an immunochromatographic D-dimer assay called 'Simplify' for diagnosis of acute DVT by complete (calf veins included) lower limb ultrasound examination.


METHODS
A total of 453 consecutive patients presented to the ED of a tertiary centre with suspected first episode of DVT, were prospectively recruited. A pre-test probability score (Hamilton Score), an immunochromatographic D-dimer and a complete, single, unilateral lower limb ultrasound examination were performed in all patients. All patients with a negative ultrasound examination were followed up for 3 months.


RESULTS
There were 159 men and 294 women with a mean age of 55.8 years (SD 20.3). Of the 227 patients with a negative D-dimer, 214 patients had negative ultrasound examinations and 13 patients had isolated calf DVT. Among the 226 patients with a positive D-dimer, 74 patients had DVT and 152 patients had negative ultrasound examinations. The sensitivity, specificity, positive and negative predictive values were 85.1% (75.8-91.8), 58.5% (53.4-63.5), 32.7% (26.6-38.9) and 94.3% (90.4-96.9), respectively. One hundred and sixty-five patients had an unlikely Hamilton Score and a negative D-dimer. The negative predictive value of the immunochromatographic D-dimer in an unlikely Hamilton Score population was 98.8% (95.7-99.8%).


CONCLUSIONS
An unlikely probability Hamilton Score and a negative immunochromatographic D-dimer reliably exclude both proximal and isolated calf DVT.
Subramaniam
Rathan M
RM
Department of Radiology, Waikato Hospital, Auckland, New Zealand. rathan67@hotmail.com
Heath
Rebekah
R
Cox
Kim
K
Chou
Tina
T
Stewart
Joanna
J
Sleigh
Jamie
J
D000328:Adult; D000368:Aged; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D011336:Probability; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000000981:diagnostic imaging
D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D