Summary
The presence and likelihood of an alternative diagnosis to pulmonary embolism is an
important variable of the Wells’ prediction rule for establishing clinical probability.
We assessed whether evoking specific alternative diagnoses would reduce the probability
of pulmonary embolism enough to forego further testing. We retrospectively studieda
cohort of 965 consecutive patients admitted for suspicion of pulmonary embolism at
three medical centers in Europe in whom the presence of an alternative diagnosis at
least as likely as pulmonary embolism was recorded before diagnostic testing. We divided
the patients into 15 categories of alternative diagnoses evoked. We then assessed
the prevalence of pulmonary embolism in each diagnostic category and compared it to
the prevalence of pulmonary embolism ina reference group (patients with no alternative
diagnosis or a diagnosis less likely than pulmonary embolism). The prevalence of pulmonary
embolism in the reference group was 48%. The presence of an alternative diagnosis
as or more likely strongly reduced the probability of pulmonary embolism (OR 0.15,
95% CI: 0.1–0.2, p<0.01). In almost every diagnostic category, the prevalence of pulmonary
embolism was much lower than in the reference group whith an odds ratio below or near
0. 2. Bronchopneumonia (OR 0.4, 95% CI 0.2 to 0.7) and cancer (OR 0.6, 95% CI 0. 3
to 1.5) reduced the likelihood of pulmonary embolism toa lower extent. Evoking an
alternative diagnosis at least as likely as pulmonary embolism reduces the probability
of the disease, but this effect is never large enough to allow ruling it out without
further testing, especially when bronchopneumonia or cancer are the alternative diagnoses
considered.
Keywords
Pulmonary embolism - alternative diagnosis - probability assessment
