Impact of reliance on CT pulmonary angiography on diagnosis of pulmonary embolism: A Bayesian analysis

Abstract

BACKGROUNDSpiral computed tomographic pulmonary angiography (CTPA) has become the primary test used to investigate suspected pulmonary embolism (PE) at many institutions, despite uncertainty regarding its sensitivity and specificity. Although CTPA‐based diagnostic algorithms focus on minimizing the false‐negative rate, we hypothesized that increasing use of CTPA also might lead to false‐positive diagnoses.OBJECTIVEDetermine the frequency of possible false‐positive diagnoses of PE when CTPA is the primary diagnostic test.DESIGNRetrospective cohort study.SETTINGTwo academic teaching hospitals.PARTICIPANTS322 patients with suspected PE evaluated with CTPA.MEASUREMENTSWe used a validated prediction rule to determine the pretest probability of PE in each patient. We combined these pretest probabilities with published estimates of CTPA test characteristics to generate expected posttest probabilities of PE. We compared these posttest probabilities to actual treatment decisions to determine the rate of false‐positive diagnoses of PE.RESULTSAmong 322 patients investigated for PE, 37 (12%) had high pretest probability, 101 (32%) moderate, and 184 (57%) low. CT scans were interpreted as positive for PE in 57 patients (17.8%). Regardless of the pretest probability of PE, 96.5% of patients with a positive CTPA were treated with anticoagulants. Even under an optimistic assumption of CTPA test characteristics, as many as 25.4% of these patients may have been treated unnecessarily as a result of a false‐positive diagnosis. Most of these patients had a low pretest probability of PE.CONCLUSIONSFailure to utilize Bayesian reasoning when interpreting CTPA may lead to false‐positive diagnoses of pulmonary embolism in a substantial proportion of patients. Journal of Hospital Medicine 2006;1:81–87. © 2006 Society of Hospital Medicine

The modified wells score accurately excludes pulmonary embolus in hospitalized patients receiving heparin prophylaxis

“…We calculated the Wells score retrospectively as was previously done in studies by Chagnon et al, 11 Righini et al, 14 and Ranji et al 27 (although the methods used in these studies were not described in detail). We assumed that whenever a d-dimer test was ordered the treating physician thought that PE was less likely than an alternate diagnosis reasoning that, if they thought PE were the most likely diagnosis, ddimers should not have been obtained as, in this circumstance, they are not recommended as part of the diagnostic algorithm.…”

Pulmonary-Vein Stenosis Can Mimic Massive Pulmonary Embolism After Radiofrequency Ablation for Atrial Fibrillation

“…CTPA is more sensitive for differentiation because it shows the positions of vein stenosis and pulmonary embolus separately. [2][3][4]13 However, with our patient the massive filling defect on CTPA misled the clinicians and radiologists to the misdiagnosis of pulmonary embolism. Actually, pulmonary-vein stenosis triggers pulmonary congestion, increases the capillary wedge pressure, and ultimately slows the pulmonary arterial flow.…”

“…7,8 However, reliance on CTPA and V /Q scan alone can lead to a falsepositive diagnosis of pulmonary embolism. 4 This teaching case is an example in point.…”

“…1 However, some CTPA findings can lead to a false-positive diagnosis of pulmonary embolism. 4 We report a patient who was misdiagnosed with pulmonary embolism after radiofrequency-catheter ablation for atrial fibrillation. Both CTPA and V /Q scan indicated a filling defect in the left main pulmonary artery, which was interpreted as a massive pulmonary embolism, but pulmonary angiography revealed that the true diagnosis was pulmonary-vein stenosis.…”

68Ga PET/CT Ventilation–Perfusion Imaging for Pulmonary Embolism: A Pilot Study with Comparison to Conventional Scintigraphy

“…Many practitioners fail to realize the limitations of imaging tests, leading to both overdiagnosis and a delay in treatment, particularly when there is discordance between clinical pretest likelihood and the imaging result. Indeed, among a cohort of 322 patients with a varying pretest likelihood of PE, Ranji et al demonstrated a 25% false-positive rate for CTPA even under optimistic assumptions of accuracy (18). Accordingly, there is a need for newer imaging modalities with higher accuracy and reproducibility.…”