Comparison of high specificity with standard versions of a quantitative latex D-dimer test in the assessment of community pulmonary embolism: HaemosIL D-dimer HS and pulmonary embolism.
BACKGROUND
D-dimer assays are sensitive but have poor specificity. False positive results lead to extra imaging and hospital admissions.


OBJECTIVE
To make a pilot comparison of the diagnostic accuracy of the standard quantitative latex HemosIL D-dimer assay with a newer HemosIL D-dimer HS version designed to have improved specificity. PATIENTS / METHODS: Consecutive patients presenting from the community to an Emergency Department that were investigated for suspected pulmonary embolism using a D-dimer test were included in the study. Standard and D-dimer HS tests were performed. Pulmonary Embolism was diagnosed on the basis of imaging studies or post-mortem at any time from presentation to 90 days thereafter.


RESULTS
The prevalence of Pulmonary Embolism was 4.5% (18/402). The sensitivity, specificity, negative predictive value, and positive predictive value for the standard quantitative D-dimer test was 100% (81.5 - 100.0), 49.2% (44.1 - 54.3),100% (98.1 - 100.0), and 8.5% (5.1 - 13.0), respectively, and 100% (81.5 - 100.0), 58.3% (53.2 - 63.3),100% (98.4 - 100.0), and 10.1% (6.1 - 15.5), for the D-dimer HS test. There were 35 (16%) fewer 'false positives' using the D-dimer HS assay compared with the standard assay.


CONCLUSIONS
D-dimer HS has superior specificity to the standard quantitative D-dimer test without any loss of sensitivity. The generation of fewer false positive results should lead to less unnecessary diagnostic imaging; the use of which is associated with increased hospital admissions and length of stay. The HS assay may therefore have significant health economic benefits.
Than
Martin P
MP
Department of Emergency Medicine, Christchurch Hospital, Christchurch, New Zealand. martin.than@cdhb.govt.nz
Helm
Jennifer
J
Calder
Kristi
K
Ardagh
Michael W
MW
Smith
Mark
M
Flaws
Dylan F
DF
Beckert
Lutz
L
D004636:Emergency Service, Hospital; D005189:False Positive Reactions; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000592:standards*; D005500:Follow-Up Studies; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D010865:Pilot Projects; D011237:Predictive Value of Tests; D015995:Prevalence; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000000981:diagnostic imaging; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology; D011859:Radiography; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013997:Time Factors
D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D