Efficacy of Ventilation Perfusion Lung Scanning and Computed Tomography Pulmonary Angiography for Chronic Thrombo-Embolic Pulmonary Hypertension

Abstract

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. Methods: 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 and classified as findings consistent with CTEPH or inconsistent with CTEPH. These classifications were independently and collectively correlated with a final diagnosis of CTEPH or no CTEPH. Results: The accuracy, sensitivity, and specificity of V/Q for detection of CTEPH was 83.5%, 57.5% 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 was 96.2%, 97.9% and 95.4% 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%, 19.2% and 98.8% respectively, with 90% PPV and 69.1% NPV. All 47 CTEPH studies were reported as having abnormal lung perfusion. Conclusion: This investigation has shown that V/Q is a more valuable diagnostic imaging tool in detecting CTEPH than CTPA. In suspected CTEPH, a high/intermediate V/Q report is consistent with a positive diagnosis. This is an important finding as CTEPH is a potentially treatable condition.