Incidental pulmonary embolism and the value of CT pulmonary angiography follow-up versus expert review

Objectives
Evaluate the prevalence of true-positive and false-positive incidental pulmonary embolism (iPE) diagnoses and the impact of expert review on diagnostic accuracy.

Methods
This single-center retrospective study included consecutive contrast-enhanced thoracic CT examinations without dedicated PE protocols which reported iPE over an 18-month period (2022-24). Electronic health records were reviewed to identify requests to confirm PE based on previous non-dedicated studies. Studies identifying iPE were graded from 1 (most certain) to 5 by original report diagnostic certainty and compared between PE-positive and PE-negative subgroups using Fisher’s exact test. Identified imaging received retrospective expert review to calculate expert agreement with CTPA, where CTPA had been performed, using Cohen’s kappa.

Results
Of 25 214 CT examinations, 260 (1%) reported iPE (mean age 73 ± 12 years; 51% women). Of these, 25% (n = 65/260) underwent confirmatory CTPA. Patients receiving CTPA had lower initial iPE diagnostic certainty (median 3 versus 1, P < .01) and 52% (n = 34/65) were PE-positive on CTPA. Patients with false-positive diagnoses had reduced diagnostic certainty on non-dedicated studies compared to those with a true-positive diagnosis (median 3 versus 2, P < .001). Agreement between the expert review of the iPE scan and the ground-truth CTPA diagnosis had κ of 0.96.

Conclusions
Expert review could be an effective tool to reduce CTPA requirement in cases of intermediate (grade 3) iPE diagnostic certainty.