A multi-center study for comparison of planar versus tomographic pulmonary ventilation/perfusion imaging for the diagnosis of pulmonary embolism

Abstract

Objective To compare between one-day planar and tomographic pulmonary V/Q imaging for the diagnosis of PE using ROC analysis.Methods From September 2010 to October 2011,272 patients suspected or confirmed of acute/sub-acute PE with Wells scores ≥ 2 or blood D-Dimer values ＞500 μg/L were recruited into this study.Patients' data were collected from six hospitals in Beijing.All patients were followed clinically for at least six months after V/Q imaging.Based on the criteria of prospective investigation of pulmonary embolism diagnosis (PIOPED) study Ⅱ,the diagnosis by planar pulmonary V/Q scans was categorized as high-probability (definite PE),moderate or low probability (suspected PE),and very low probability or normal lung perfusion (no PE).The diagnosis by SPECT V/Q scans was also classified as definite PE,suspected PE and no PE.The final diagnosis was decided by doctors in consensus based on the results of multiple imaging modalities,laboratory tests,clinical data and a six-month follow-up.Kappa test was used to analyze the concordance between planar and tomographic V/Q scans.The difference between the two methods was tested using x2 test.ROC analysis was used to determine the AUCs.Z test was used to calculate the statistical significance of the difference between the AUCs.Results The uncertain diagnosis rate was 1.8％ (5/272) for V/Q SPECT and 9.2％ (25/272) for planar imaging.The diagnostic values for SPECT and planar V/Q scans were respectively:Se 83.6％ (117/140) and 78.3％ (101/129)(x2=1.217,P＞0.05); Sp89.8％(114/127) and 94.9％(112/118) (x2 =2.269,P＞0.05); PPV 90.0％ (117/130) and 94.4％ (101/107) ; NPV 83.2％ (114/137) and 80.0％ (112/140) ; Ac 86.5％ (231/267) and 86.2％ (213/247).There were no significant differences in Se and Sp between the two methods.The concordance between the two methods was 84.9％ (231/272,Kappa =0.727,P ＜ 0.05).The AUC (95％ CI) was 0.891 (0.848-0.933) and 0.865 (0.819-0.911) for SPECT and planar V/Q,respectively (Z =2.65 and 2.03,both P ＜ 0.05).Conclusion Pulmonary V/Q imaging using tomographic techniques combined with ROC analysis may significantly improve the diagnostic accuracy of PE when compared with the conventional planar technique. Key words: Pulmonary embolism ; Radionuclide imaging; Tomography, emission-computed,single-photon; Technetium ; MAA