Perfusion SPECT in patients with suspected pulmonary embolism

Abstract

Purpose Ventilation/perfusion tomography (V/P SPECT ), with new interpretation criteria and newer tracers for ventilation imaging, has markedly improved the diagnostic yield in acute pulmonary embolism (PE). Here, we evaluated the diagnostic performance of perfusion SPECT (P SPECT ) without ventilation imaging. Methods We studied 152 patients with clinically suspected PE who had been examined with both V/P SPECT and multidetector computed tomographic angiography (MD-CTA). The diagnosis or exclusion of PE was decided by the referring clinician based on both the V/P SPECT and/or MD-CTA findings in combination with the clinical findings. P SPECT images were retrospectively examined by a physician with experience in the interpretation of planar perfusion scans who was blinded to clinical, V/P SPECT and MD-CTA data. P SPECT images were interpreted without the aid of chest radiography. All the patients who were deemed to have PE were given anticoagulant therapy. Results Of the 152 patients, 59 (39 %) received a final diagnosis of PE, and 19 (32 %) had associated cardiopulmonary diseases such as pneumonia, COPD, or left heart failure. P SPECT correctly identified 53 (90 %) of the 59 patients with PE. The specificity was 88 of 93 (95 %). None of the P SPECT images was rated nondiagnostic. P SPECT yielded an overall diagnostic accuracy of 93 % (95 % confidence interval, CI, 87-96 %). At the observed PE prevalence of 39 %, the positive and negative predictive values of P SPECT were 91 % (95 % CI, 80-97 %) and 94 % (95 % CI, 86-97 %), respectively. Conclusion In managing critically ill patients, P SPECT might be a valid alternative to V/P SPECT or MD-CTA since it was able to identify most patients with PE with a low falsepositive rate and no inconclusive results.

Good clinical practice in pulmonary embolism diagnosis: where do we stand today?

“…Perfusion SPECT is only recommended in emergencies when the diagnosis of PE would otherwise be missed as pointed out in a recent article and editorial [11,12].…”

Critical review of SPECT imaging in pulmonary embolism

“…Bajc et al suggested that perfusion SPECT (without ventilation SPECT) might be a valid alternative to V/Q SPECT or multidetector CT angiography in critically ill patients [36]. Its sensitivity was 53 out of 59 (90 %) and its specificity was 88 out of 93 (95 %).…”

“…The specificity ranged from 71 to 100 % [21,22,24,[26][27][28][29][30][31][32][33][34][35][36] except in a single investigation of six patients without PE, in which the specificity was 0 out of 6 (0 %) [25]. The agents used for V SPECT differed (Table 1) and the diagnostic criteria for interpretation of SPECT also differed among investigations (Table 1).…”

“…Across all investigations, the sensitivity of V/Q SPECT ranged from 55 to 100 % [21,22,[24][25][26][27][28][29][30][31][32][33][34][35][36] (Table 1). The specificity ranged from 71 to 100 % [21,22,24,[26][27][28][29][30][31][32][33][34][35][36] except in a single investigation of six patients without PE, in which the specificity was 0 out of 6 (0 %) [25].…”

“…The study design contributed to the low specificity. When comparing individual lung segments, the sensitivity of SPECT was 56 out of 62 (90 %) and the specificity 75 out of 118 (64 %) ( Table 1) V/Q SPECT using composite reference standards Most investigations of the sensitivity and specificity of V/Q SPECT included the index test (SPECT) or planar V/Q results in the composite reference standard [21,22,[24][25][26][27][28][29][30][31][32][33][34][35][36] ( Table 1). This would introduce incorporation bias [18,37], which can be expected to result in an overestimation of the diagnostic accuracy [18,38].…”