Diagnostic performance of lung perfusion and CTPA for CTEPH among a Southeast Asia Population

Introduction:
The diagnostic approach for patients with suspected Chronic Thrombo-Embolic Pulmonary Hypertension (CTEPH) is a combination of clinical and pre-test probability assessment, and diagnostic imaging of computed tomography pulmonary angiogram (CTPA) or lung ventilation and perfusion scintigraphy (V/Q). There is a paucity of literature, particularly for Southeast Asia (SEA) populations, regarding the efficacy of these imaging approaches. This study investigated the sensitivity and specificity of V/Q and CTPA in the diagnosis of CTEPH in SEA patients.

Method/Approach:
A retrospective analysis was undertaken on 133 consecutive patients presenting for pulmonary hypertension (PH). The population included 42 males, 91 females, 683 V/Q images and 6288 CTPA images for patients in the age range 18 to 93 years (mean 66). All data was retrospectively analysed by two nuclear medicine physicians/radiologists and classified as findings consistent with CTEPH or inconsistent with CTEPH. These classifications were independently and ollectively correlated with a final diagnosis of CTEPH or no CTEPH, made as a collective clinical decision by the primary attending physician based on the results of
relevant investigations.

Results:
The accuracy, sensitivity, and specificity of V/Q for detection of CTEPH were 83.5%, 57.4% and 97.7% respectively, with a positive predictive value (PPV) of 93.1% and a negative predictive value (NPV) of 80.8% when only high probability reports were considered CTEPH positive. The accuracy, sensitivity, and specificity of V/Q for detection of CTEPH were 96.2%, 97.9% and 95.3% respectively, with a PPV of 92.0% and a NPV of 98.8% when both high probability and intermediate probability reports were considered CTEPH positive. The accuracy, sensitivity
and specificity of CTPA for detection of CTEPH were 70.7%, 19.1% and 98.8% respectively, with 90% PPV and 69.1% NPV. All 47 CTEPH positive studies were reported as having abnormal lung perfusion scans.

Conclusion:
This study demonstrated the higher diagnostic efficacy of V/Q over CTPA in diagnosing CTEPH in the SEA population. At the same time, in addressing the study objective, a normal lung perfusion has shown to exclude the presence of CTEPH in PH patients. Perfusion imaging is recommended first in eliminating the need for ventilation if perfusion is normal.