Abstract
Introduction: The diagnostic approach to patients with suspected pulmonary embolism (PE) and its clinical complication of chronic thromboembolic pulmonary hypertension (CTEPH) is usually a combination of clinical and pretest probability assessments, and definitive diagnostic imaging. Diagnostic studies and imaging procedures, such as ventilation and perfusion scintigraphy (V/Q), computed tomography (CT), pulmonary angiography, and CT pulmonary angiogram (CTPA), play an important role and have proven to be excellent complements in accurately confirming or ruling out the presence of PE and CTEPH. The purpose of this review is to compare and aggregate the available data from PE and CTEPH diagnosis studies carried out using the imaging techniques of CTPA, single-photon emission CT (SPECT) V/Q, and planar V/Q.
Methods: A systemic review was conducted with participants who were limited to patients with or suspected with PE or CTEPH. No age limitations, geographic, and gender differentiations were imposed. Pooled sensitivity and specificity performances, positive and negative likelihood ratio (LR), the I-square (I2) value of heterogeneity SROC curves, and the area under the curve were generated. The Q* value was calculated to define the point where sensitivity and specificity are equal.
Results: Twenty-six studies totalling 5,637 patients were reviewed. The majority of the studies included the comparison of techniques within or between the different imaging modalities. For PE, the patient pool for CTPA was 904, for SPECT V/Q was 3717, and for planar V/Q was 1016, with sensitivity of 84%, 94%, and 85%, respectively, and corresponding specificity of 94%, 99%, and 85%, respectively. For CTEPH, the patient pool for CTPA was 488 for patient-based and 2,538 vessels for vessel-based, and for V/Q was 530, with sensitivity of 76%, 95%, and 98%, respectively, and corresponding specificity of 95%, 96%, and 93%, respectively.
Conclusion: This review demonstrated superior sensitivity and specificity of V/Q SPECT over CTPA and planar V/Q for the diagnosis of PE. Likewise, for CTEPH, V/Q demonstrated superior sensitivity and specificity, although in a select subgroup of CTPA patients assessed on a per vessel basis, performance was improved. Wherever available, V/Q SPECT should be used as the first line imaging tool for PE and CTEPH.

Key words: Lung scan, ventilation, perfusion, pulmonary hypertension, CTPA, VQ.