Mandatory adherence to diagnostic protocol increases the yield of CTPA for pulmonary embolism

Objectives: To determine if mandatory adherence to a diagnostic protocol increases the rate of computed tomography pulmonary angiographies (CTPAs) positive for pulmonary embolism (PE)-the so-called diagnostic yield. Further, we aim to identify factors associated with this diagnostic yield.

Methods: We included all patients with suspected PE requiring CTPA from 9 January 2014 t0 3 June 2014. The requesting physicians were forced to follow diagnostic workup for PE by calculating a Wells score and, if necessary, determining D-dimer level. The percentage of positive CTPA scans was calculated and compared with our previous cohort (Walen et al. Insights Imaging 2014;5(2):231-236). Odds ratios were calculated as a measure of association between dichotomous variables and CTPA findings.

Results: Of 250 scans, 74 were positive (29.6 % [95 % CI, 24.3-35.5 %]) and 175 were negative (70 %). The percentage positive scans increased with 6.6 % and the percentage negative scans decreased with 3.1 %. This change was statistically significant (p = 0.001). Independent clinical predictors of diagnostic yield were previous deep venous thrombosis (DVT) (OR, 3.22; p = 0.013) and clinical signs of DVT (OR, 2.71; p = 0.012). Chronic obstructive pulmonary disease (COPD) was negatively associated with PE (OR, 0.33; p = 0.045).

Conclusions: This study shows that mandatory adherence to a diagnostic protocol increases the yield of CTPA for PE in our centre.

Main messages: • Mandatory adherence to diagnostic protocol increases the yield of CTPA for PE • Previous DVT and signs of DVT were associated with a higher yield • No patients with a low Wells score and a low D-dimer had PE.