Prevalence and Significance of Incidental Findings on CTPA

Written by Bo Stubblefield

Spoon Feed
Computed tomography pulmonary angiography (CTPA) yields an alternative diagnosis to pulmonary embolism (PE) in ~40% of patients with a negative PE study. Alternative diagnoses are more likely to occur in patients with increased age and in patients referred from the hospital setting (ICU or inpatient unit).

Why does this matter?
Over-imaging for suspected PE in US emergency departments (ED) is a public health problem. Diagnostic yield positive for PE has been reported at ~1-3% in newer studies.1,2 The incidence of PE in both the US and Europe has increased in the last two decades while the case-fatality rate has decreased.3-5 It is postulated we are diagnosing more PEs with less clinically severe disease burden.6,7 With increased rates of imaging, what is the prevalence of incidental findings on CTPA? What is the prevalence of an alternative diagnosis?

Prettayyyyy, prettayyy likely to be something other than a PE…
This was a retrospective study of 2,083 patients with CTPA results negative for acute PE. Eskandari, et al. classified incidental CTPA findings as Type-1 (emergent diagnoses other than PE that could explain the patient’s symptoms of chest pain or dyspnea), Type-2 (non-emergent findings that would require further work-up), and Type-3 (non-emergent findings likely unrelated to patient’s acute presentation).

Authors report that nearly 75% of patients had at least one incidental finding and ~40% patients had a finding that was an alternative diagnosis for PE. The top 3 most common alternative diagnoses were 1) pneumonia; 2) fluid overload; 3) pleural effusion. Patients in ICU or inpatient settings had increased odds of identifying an alternative diagnosis on CTPA when compared to the ED or outpatient locations.

This study is novel in that it included patients from ED, ICU, inpatient, and outpatient settings. It reaffirms differences in patient characteristics across clinical settings, and differences in older patients who have higher odds of an alternative diagnosis on CTPA. Imaging can be helpful when used in specific populations. Let’s continue to use our clinical decision tools and the D-dimer in the ED for low to moderate risk patients with suspected PE.

Another Spoonful
Is it a novel finding that pneumonia was the most identified diagnosis on CTA in patients with suspect pulmonary embolism? Nah. Hall, et al. and Van Es, et al. both found pneumonia to be the most identified alternative diagnosis in 2009 and 2013, respectively.8,9 Jeff Kline (@klinelab) has used this as a teaching point for years. Here is the PE guru himself is chatting about it in 2014 (26:52) while discussing the ADJUST-PE Trial.

Prevalence and significance of incidental findings on computed tomography pulmonary angiograms: A retrospective cohort study. Am J Emerg Med. 2022 Apr;54:232-237. doi: 10.1016/j.ajem.2022.01.064.

Works Cited

  1. Kline JA, Garrett JS, Sarmiento EJ, Strachan CC, Courtney DM. Over-Testing for Suspected Pulmonary Embolism in American Emergency Departments: The Continuing Epidemic. Circ Cardiovasc Qual Outcomes 2020;13:e005753.
  2. Dhakal P, Iftikhar MH, Wang L, et al. Overutilisation of imaging studies for diagnosis of pulmonary embolism: are we following the guidelines? Postgrad Med J 2019;95:420-4.
  3. Bikdeli B, Wang Y, Jimenez D, et al. Pulmonary Embolism Hospitalization, Readmission, and Mortality Rates in US Older Adults, 1999-2015. Jama 2019;322:574-6.
  4. Keller K, Hobohm L, Ebner M, et al. Trends in thrombolytic treatment and outcomes of acute pulmonary embolism in Germany. European heart journal 2020;41:522-9.
  5. Lehnert P, Lange T, Moller CH, Olsen PS, Carlsen J. Acute Pulmonary Embolism in a National Danish Cohort: Increasing Incidence and Decreasing Mortality. Thrombosis and haemostasis 2018;118:539-46.
  6. Gerstein L, Koolian M, Schwartz BC. Sub-segmental pulmonary emboli as a marker of CT-pulmonary angiogram overuse in a single-center retrospective cohort study: A dimer a dozen? Thrombosis research 2020;196:463-5.
  7. Schissler AJ, Rozenshtein A, Kulon ME, et al. CT pulmonary angiography: increasingly diagnosing less severe pulmonary emboli. PloS one 2013;8:e65669.
  8. Hall WB, Truitt SG, Scheunemann LP, et al. The prevalence of clinically relevant incidental findings on chest computed tomographic angiograms ordered to diagnose pulmonary embolism. Arch Intern Med 2009;169:1961-5.
  9. van Es J, Douma RA, Schreuder SM, et al. Clinical impact of findings supporting an alternative diagnosis on CT pulmonary angiography in patients with suspected pulmonary embolism. Chest 2013;144:1893-9.

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