Well's Score = 0
Pretest probability of PE = 3.4%

Score to Pretest Probability:

The generally accepted "miss rate" for PE is 2%, meaning Well's alone cannot "rule out" PE with acceptable sensitivity. One method for clinically excluding PE is to apply the PERC rule if Well's score is ≤ 2-4.

For patients with high pretest probability of PE (ex: higher Well's Scores), D dimer does not exclude the diagnosis even if negative.

A study in 2007 (see below) found that in patients with Well's Score ≤ 4 and a negative ELISA D dimer assay (Vidas), 0.4% had a PE (2 patients, in both cases further testing was not clearly indicated).

D dimer can be measured using quantitative latex agglutination test (sensitivity 85-90%), whole blood agglutination (sens. 85-90%), or ELISA (sens. >95%, spec. 40%).

Suggested algorithm for PE workup, by EM:RAP / Cameron Berg:

 

Wells PS et al. Derivation of a simple clinical model to categorize patients' probability of pulmonary embolism: increasing the model utility with the SimpliRED d dimer. Thromb Haemost. 2000; 83:418.

Goekoop, RJ et al. Simple and safe exclusion of pulmonary embolism in outpatients using quantitative D-dimer and Wells' simplified decision rule. Thromb Haemost. 2007; 97(1):146-50.

Orman, Rob and Berg, Cameron. Accelerated Diagnostic Pathway: PE. EM:RAP. May 2015. Link