• Michael Perera, Leena Aggarwal, Ian A Scott, and Nicholas Cocks.
• Department of General and Acute Medicine, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
• Intern Med J. 2017 Oct 1; 47 (10): 1154-1160.

BackgroundEvidence suggests the potential overuse of computed tomography pulmonary angiography (CTPA) in patients with suspected pulmonary thromboembolism (PTE) in the absence of consistent use of pre-test clinical prediction rules and D-dimer assays.AimTo evaluate use and diagnostic utility of clinical prediction rules and D-dimer assay in patients with suspected PTE and quantify potentially avoidable overuse of CTPA in low risk patients.MethodsA total of 344 consecutive patients undergoing CTPA at a tertiary hospital was studied with regards to the use of D-dimer assays and clinical prediction rules for PTE. For each patient, a modified Wells score (mWS), revised Geneva score and PISA model were calculated retrospectively; performance characteristics for each rule for PTE were determined with reference to results of CTPA. Results for the mWS and D-dimer assays (when performed) were used to estimate the overuse of CTPA according to risk category.ResultsUse of a clinical prediction rule was documented in only 5.0% of cases. Of 269 low-risk patients who had a calculated mWS ≤4, only 64 (23.8%) had a D-dimer assay performed, with 30 (11.1%) having a PTE on CTPA. Among 75 patients with an mWS >4, 23 (30.7%) had a PTE on CTPA (P < 0.001). Compared to other prediction rules, an mWS>4 had the highest positive predictive value (31.0%) for PTE; all rules demonstrated similar negative predictive values for low-risk scores (87-89%). After adjusting for an 11% false negative rate for PTE in patients with low-risk mWS, overuse of CTPA was reported in up to 190 (55.2%) patients.ConclusionMore than 50% of patients with suspected PTE may be subject to unwarranted use of CTPA in the absence of pre-test clinical prediction rules coupled with D-dimer assays.© 2017 Royal Australasian College of Physicians.

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