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Pulmonary embolism rule out: positivity and factors affecting the yield of CT angiography
  1. Tanya Aggarwal1,
  2. Ali Eskandari2,
  3. Sarv Priya1,
  4. Aidan Mullan3,
  5. Ishan Garg4,
  6. Jakub Siembida1,
  7. Brian Mullan1,
  8. Prashant Nagpal1
  1. 1 Department of Radiology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
  2. 2 Department of Radiology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
  3. 3 Statistics, University of California Berkeley, Berkeley, California, USA
  4. 4 Mayo Clinic Rochester, Rochester, Minnesota, USA
  1. Correspondence to Dr Prashant Nagpal, Radiology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA; drprashantnagpal{at}


Objective CT pulmonary angiography (CTPA) is one of the most commonly ordered CT imaging tests. It is often believed to be overutilised with few recent studies showing a yield of less than 2%. This study aimed to determine the overall positivity rate of CTPA examinations and understand the factors that affect the yield of the CTPA examination.

Methods We retrospectively analysed 2713 patients who received the CTPA exam between 2016 and 2018. Type of study ordered (CTPA chest or CTPA chest with abdomen and pelvis CT), patient location (emergency department (ED), outpatient, inpatient, intensive care unit (ICU)) and patient characteristics—age, sex and body mass index (BMI) were recorded. A logistic regression analysis was performed to determine what factors affect the positivity rate of CT scans for pulmonary embolism (PE).

Results With 296 positive test results, the overall CTPA positivity was 10.9%. Male sex was associated with higher CTPA positivity, gender difference was maximum in 18-year to 35-year age group. Overweight and obese patients had significantly higher positivity as compared with BMI<25 (p<0.05). Higher positivity rate was seen in the BMI 25–40 group (11.9%) as compared with BMI>40 (10.1%) (p<0.05). Significant difference (p<0.001) was also found in CTPA examination yield from ICU (15.3%) versus inpatients (other than ICU) (12.4%) versus ED (9.6%), and outpatients (8.5%). The difference in CTPA yield based on the type of CT order (CTPA chest vs CTPA chest with CT abdomen and pelvis), patient’s age and sex was not significant.

Conclusion CTPA yield of 10.9% in this study is comparable to acceptable positivity rate for the USA and is higher than recent studies showing positivity of <2%. Patient characteristics like obesity and ICU or inpatient location are associated with higher rate of CT positivity.

  • pulmonary embolism
  • CT angiography
  • thromboembolism

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  • Contributors PN, BFM and AE formulated the idea. TA, SP and PN wrote the manuscript. AE, SP and JS collected the data. AM and IG helped with the methodology and statistics for the project. All authors had access to the anonymised data and a role in editing the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval University of Iowa Institutional Research Review Board. IRB ID - 201812764.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. De-identified participant data may be made available after individual request approval by the institutions IRB.