The importance of clinical probability assessment in interpreting a normal d-dimer in patients with suspected pulmonary embolism.
BACKGROUND
The d-dimer test is widely applied in the diagnostic workup of patients with suspected pulmonary embolism (PE). The objective of this study was to investigate how often the d-dimer test fails when clinical probability is not taken into account.


METHODS
We used data collected in 1,722 consecutive patients with clinically suspected PE to analyze the 3-month venous thromboembolism (VTE) rate in all patients with a normal d-dimer concentration and separately for patients who have a normal d-dimer concentration with an unlikely or likely clinical probability for PE, as assessed by the Wells clinical decision rule.


RESULTS
The 3-month VTE rate in all patients with a normal d-dimer concentration (n = 563) was 2.3% (95% confidence interval [CI], 1.4 to 3.9%). In the patients with an unlikely probability of PE (n = 477), VTE was confirmed in 1.1% of the patients with a normal d-dimer concentration (95% CI, 0.4 to 2.4%). In those patients with a likely clinical probability of PE (n = 86), VTE was confirmed in 9.3% of the patients with a normal d-dimer concentration (95% CI, 4.8 to 17.3%). The difference in VTE incidence between patients with unlikely and likely clinical probabilities of PE was significant (p < 0.001).


CONCLUSIONS
Our findings indicate that it is of utmost importance to first examine the patient and assess the clinical probability, after which the d-dimer concentration can be taken into account, in order to prevent physicians from being influenced by a normal d-dimer test result when they evaluate the clinical probability of PE. Patients with a likely clinical probability should undergo further testing, regardless of the d-dimer test outcome.
Gibson
Nadine S
NS
Department of Vascular Medicine, Academical Medical Center, Amsterdam, the Netherlands. Electronic address: n.s.gibson@amc.uva.nl.
Sohne
Maaike
M
Department of Vascular Medicine, Academical Medical Center, Amsterdam, the Netherlands.
Gerdes
Victor E A
VEA
Department of Vascular Medicine, Academical Medical Center, Amsterdam, the Netherlands.
Nijkeuter
Mathilde
M
Department of General Internal Medicine, Leiden University Medical Center, Leiden, the Netherlands.
Buller
Harry R
HR
Department of Vascular Medicine, Academical Medical Center, Amsterdam, the Netherlands.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003661:Decision Support Techniques; D005188:False Negative Reactions; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000209:etiology*; D012189:Retrospective Studies; D018570:Risk Assessment; D054556:Venous Thromboembolism / Q000097:blood / Q000175:diagnosis* / Q000209:etiology*
D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D