Abstract Rationale To directly compare the diagnostic performance and inter-modality agreement of lung perfusion single-photon emission computed tomography/computed tomography (SPECT/CT), using perfusion defect criteria, with computed tomography pulmonary angiography (CTPA) in patients with suspected pulmonary thromboembolism (PTE). Methods We retrospectively analyzed 38 patients who underwent both perfusion SPECT/CT and CTPA within one week. Perfusion SPECT/CT was interpreted for wedge-shaped perfusion defects without corresponding CT abnormalities. CTPA was evaluated for intraluminal filling defects. Final diagnosis of PTE was determined by treating physicians based on clinical, laboratory, and imaging findings. Sensitivity, specificity, predictive values, and overall accuracy were calculated. Inter-modality agreement was assessed using McNemar’s test and Cohen’s kappa. Results CTPA demonstrated a sensitivity of 77.3%, specificity of 81.3%, and overall accuracy of 79.0%. Perfusion SPECT/CT showed higher sensitivity (81.8%) but lower specificity (68.8%), with accuracy of 76.3%. Positive predictive values were 85.0% for CTPA and 78.3% for SPECT/CT, while negative predictive values were 72.2% and 73.3%, respectively. Between the two modalities, 14 cases were concordantly positive and 9 cases were concordantly negative, whereas 15 cases were discordant (6 CTPA-positive but SPECT-negative; 9 SPECT-positive but CTPA-negative). McNemar’s test revealed no significant discordance (p=0.606). Cohen’s kappa was 0.20, indicating slight agreement. Coclusions CTPA provides higher specificity and overall accuracy, whereas perfusion SPECT/CT offers higher sensitivity, yielding nearly comparable diagnostic performance. Given the modest agreement (14 concordant positive, 9 concordant negative, 15 discordant), the two modalities appear complementary, and combined use may enhance diagnostic confidence, particularly when one modality is limited or contraindicated. This abstract is funded by: None
C Lim (Fri,) studied this question.