Analysis of the ventilation scan in the evaluation of CTEPH

Introduction: Early diagnosis of acute pulmonary embolism (PE) and a subsequent fast response in thrombolytics treatment is a key element in preventing progression to Chronic Thrombo-Embolic Pulmonary Hypertension (CTEPH). Lung ventilation and perfusion scintigraphy (V/Q) has been widely accepted as the preferred initial diagnostic imaging screening procedure for CTEPH. This study aimed to evaluate the performance of different ventilation methods in detecting CTEPH.
Methods: Data of completed V/Q studies and reports of 167 consecutive patients for further investigation of suspected CTEPH, were retrieved for analysis. All data was retrospectively analysed by two nuclear medicine physicians. The specificity, sensitivity, accuracy, positive predictive values (PPV), and negative predictive values (NPV), false positive rate and false negative rate of V/Q and CTPA were derived and calculated from these data.
Results: Of the 167 patients, 64 (38.3%) had a final diagnosis of CTEPH. While there were 64 positive cases for CTEPH, CTPA was positive for only 18 while the VQ was positive for all 64. Compared to DTPA aerosol, Technegas demonstrated superior positive predictive value, sensitivity and specificity with comparable negative predictive value and accuracy.
Conclusion: In suspected CTEPH, a high/intermediate V/Q report is consistent with a positive diagnosis. The use of Technegas for ventilation improves the positive predictive value and sensitivity over aerosol ventilation.