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............................................................................................................................................................................. commonplace tests such as chest X-rays and electrocardiograms for differential diagnosis. However, as clinical judgement lacks standardization, several explicit clinical prediction rules have been developed. Of these, the most frequently used prediction rules are the revised Geneva rule (Table 5) and the Wells rule (see Supplementary Data Table 1).86 Both prediction rules have been simplified in an attempt to increase their adoption into clinical practice;87,88 the simplified versions have been externally validated.89,90

Regardless of the score used, the proportion of patients with confirmed PE can be expected to be 10% in the low-probability category, 30% in the moderate-probability category, and 65% in the highprobability category.92 When the two-level classification is used, the proportion of patients with confirmed PE is 12% in the PE-unlikely category and 30% in the PE-likely category.92 A direct prospective comparison of these rules confirmed a similar diagnostic performance.89

4.3 Avoiding overuse of diagnostic tests

for pulmonary embolism Searching for PE in every patient with dyspnoea or chest pain may lead to high costs and complications of unnecessary tests. The Pulmonary Embolism Rule-out Criteria (PERC) were developed for emergency department patients with the purpose of selecting, on clinical grounds, patients whose likelihood of having PE is so low that diagnostic workup should not even be initiated.93 They comprise eight clinical variables significantly associated with an absence of PE: age < 50 years; pulse < 100 beats per minute; SaO2 >94%; no unilateral leg swelling; no haemoptysis; no recent trauma or surgery; no history of VTE; and no oral hormone use. The results of a prospective validation study,94 and those of a randomized non-inferiority management study,95 suggested safe exclusion of PE in patients with low clinical probability who, in addition, met all criteria of the PERC rule. However, the low overall prevalence of PE in these studies94,95 does not support the generalizability of the results.

4.4 D-dimer testing

D-dimer levels are elevated in plasma in the presence of acute thrombosis because of simultaneous activation of coagulation and fibrinolysis. The negative predictive value of D-dimer testing is high, and a normal D-dimer level renders acute PE or DVT unlikely. On the other hand, the positive predictive value of elevated D-dimer levels is low and D-dimer testing is not useful for confirmation of PE. D-dimer is also more frequently elevated in patients with cancer,96,97 in hospitalized patients,89,98 in severe infection or inflammatory disease, and during pregnancy.99,100 Accordingly, the number of patients in whom D-dimer must be measured to exclude one PE (number needed to test) rises from 3 in the general population of an emergency department to >_10 in the specific situations listed above. As a number of D-dimer assays are available, clinicians should become aware of the diagnostic performance of the test used in their own hospital. The quantitative enzyme-linked immunosorbent assay (ELISA) or ELISA-derived assays have a diagnostic sensitivity of >_95%, and can be used to exclude PE in patients with either low or intermediate pre-test probability. In the emergency department, a negative ELISA D-dimer can, in combination with clinical probability, exclude the disease without further testing in 30% of patients with suspected PE.101103 Outcome studies have shown that the 3 month thrombo- embolic risk was <1% in patients with low or intermediate clinical probability who were left untreated on the basis of a negative test result.104

4.4.1 Age-adjusted D-dimer cut-offs The specificity of D-dimer in suspected PE decreases steadily with age to 10% in patients >80 years of age.105 The use of age-adjusted cutoffs may improve the performance of D-dimer testing in the elderly. A multinational prospective management study evaluated a previously validated age-adjusted cut-off (age  10 mg/L, for patients aged >50 years) in a cohort of 3346 patients.106 Patients with a normal ageadjusted D-dimer value did not undergo CTPA; they were left untreated and followed for a 3 month period. Among the 766 patients who were >_75 years of age, 673 had a non-high clinical probability. Use of the age-adjusted (instead of the ‘standard’ 500 mg/L) D-dimer cut-off increased the number of patients in whom PE could be excluded from 6.4 to 30%, without additional false-negative findings.106

4.4.2 D-dimer cut-offs adapted to clinical probability A prospective management trial used the ‘YEARS’ clinical decision rule, which consists of three clinical items of the Wells score (see Supplementary Data Table 1)—namely signs of DVT, haemoptysis, and PE more likely than an alternative diagnosis—plus D-dimer concentrations.107 PE was considered to be excluded in patients without clinical items and D-dimer levels <1000 ng/mL, or in patients with one or more clinical items and D-dimer levels <500 ng/mL. All other patients underwent CTPA. Of the 2946 patients (85%) in whom PE was ruled out at baseline and who were left untreated, 18 [0.61%, 95% confidence interval (CI) 0.360.96%] were diagnosed with symptomatic VTE during the 3 month follow-up. CTPA was avoided in 48% of the included patients using this algorithm, compared to 34% if the Wells rule and a fixed D-dimer threshold of 500 ng/mL would have been applied.107

4.4.3 Point-of-care D-dimer assays In certain situations, notably in community or primary care medicine, ‘on-the-spot’ D-dimer testing may have advantages over referring a patient to a central laboratory for D-dimer testing. This may particularly apply to remote areas where access to healthcare is limited.108,109 However, point-of-care assays have a lower sensitivity and negative predictive value compared with laboratory-based D-dimer tests. In a systematic review and meta-analysis, sensitivity of point-ofcare D-dimer assays was 88% (95% CI 8392%) whereas conventional laboratory-based D-dimer testing had a sensitivity of at least 95%.110 As a result, point-of-care D-dimer assays should only be used in patients with a low pre-test probability. In these situations, PE could be ruled out in 46% of patients with suspected PE without proceeding to imaging tests (with a failure rate of 1.5%), as suggested by a prospective study in Dutch primary care.111

4.5 Computed tomographic pulmonary

angiography Multidetector CTPA is the method of choice for imaging the pulmonary vasculature in patients with suspected PE. It allows adequate visualization of the pulmonary arteries down to the subsegmental level.112114 The Prospective Investigation On Pulmonary Embolism Diagnosis (PIOPED) II study observed a sensitivity of 83% and a Downloaded from academic.oup.com/eurheartj/article/41/4/543/5556136 by guest on 07 October 2026