A diagnostic strategy involving a quantitative latex D-dimer assay reliably excludes deep venous thrombosis.
BACKGROUND
Because clinical diagnosis is inaccurate, objective testing is usually considered necessary when patients present with suspected deep venous thrombosis (DVT).


OBJECTIVE
To determine whether a negative result on a quantitative latex D dimer assay eliminates the need for further investigation in patients with a low or moderate pretest probability of DVT.


METHODS
Prospective cohort study.


METHODS
Three tertiary care hospitals in Canada.


METHODS
556 consecutive outpatients with suspected first DVT.


METHODS
Patients were categorized as having a low, moderate, or high pretest probability of DVT and then underwent D-dimer testing. Patients with low or moderate pretest probability and a negative D-dimer result had no further diagnostic testing and received no anticoagulant therapy. Serial compression ultrasonography was performed in all other patients. Patients who did not receive a diagnosis of DVT were followed for symptomatic venous thromboembolism.


METHODS
Objectively confirmed symptomatic venous thromboembolic events during 3 months of follow-up.


RESULTS
283 patients (51%) had low or moderate pretest probability and a negative D-dimer result. One of these patients had DVT during follow-up (negative likelihood ratio, 0.05 [CI, 0.01 to 0.23]). The negative likelihood ratio of the d -dimer test in all patients was 0.03 (CI, 0.01 to 0.16).


CONCLUSIONS
A negative result on a quantitative latex d -dimer assay safely eliminates the need for further testing in patients with low or moderate pretest probability of DVT.
Bates
Shannon M
SM
McMaster University Medical Centre, HSC 3W11, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada. batesm@mcmaster.ca
Kearon
Clive
C
Crowther
Mark
M
Linkins
Lori
L
O'Donnell
Martin
M
Douketis
Jim
J
Lee
Agnes Y Y
AY
Weitz
Jeffrey I
JI
Johnston
Marilyn
M
Ginsberg
Jeffrey S
JS
D005338:Fibrin Fibrinogen Degradation Products; D006801:Humans; D007841:Latex Fixation Tests / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D014463:Ultrasonography; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000000981:diagnostic imaging
D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D