Lung scintigraphy in the diagnosis of pulmonary embolism: current methods and interpretation criteria in clinical practice

Abstract

BackgroundIn current clinical practice lung scintigraphy is mainly used to exclude pulmonary embolism (PE). Modified diagnostic criteria for planar lung scintigraphy are considered, as newer scitigraphic methods, especially single photon emission computed tomography (SPECT) are becoming more popular.Patients and methods.Data of 98 outpatients who underwent planar ventilation/perfusion (V/Q) scintigraphy and 49 outpatients who underwent V/Q SPECT from the emergency department (ED) were retrospectively collected. Planar V/Q images were interpreted according to 0.5 segment mismatch criteria and revised PIOPED II criteria and perfusion scans according to PISA-PED criteria. V/Q SPECT images were interpreted according to the criteria suggested in EANM guidelines. Final diagnosis of PE was based on the clinical decision of an attending physician and evaluation of a 12 months follow-up period.ResultsUsing 0.5 segment mismatch criteria and revised PIOPED II, planar V/Q scans were diagnostic in 93% and 84% of cases, respectively. Among the diagnostic planar scans readings specificity for 0.5 segment mismatch criteria was 98%, and 99% for revised PIOPED II criteria. V/Q SPECT showed a sensitivity of 100% and a specificity of 98%, without any non-diagnostic cases. In patients with low pretest probability for PE, planar V/Q scans assessed by 0.5 segment mismatch criteria were diagnostic in 92%, and in 85% using revised PIOPED II criteria, while perfusion scintigraphy without ventilation scans was diagnostic in 80%.ConclusionsLung scintigraphy yielded diagnostically definitive results and is reliable in ruling out PE in patients from ED. V/Q SPECT has excellent specificity and sensitivity without any non-diagnostic results. Percentage of non-diagnostic results in planar lung scintigraphy is considerably smaller when 0.5 segment mismatch criteria instead of revised PIOPED II criteria are used. Diagnostic value of perfusion scintigraphy according to PISA-PED criteria is inferior to combined V/Q scintigraphy; the difference is evident especially in patients with low pretest probability for PE.

Ventilation/perfusion SPECT for the diagnosis of pulmonary embolism: A systematic review

“…Thirteen diagnostic accuracy studies met the inclusion criteria. [26][27][28][29][30][31][32][33][34][35][36][37][38] Study characteristics are depicted in Table S1. Twelve (92%) were single-institution studies.…”

“…Domain 1: patient selection. The risk of bias in patient selection was judged as low, high, and unclear in three, 30,34,36 eight, 26,27,29,[31][32][33]37,38 and two 28,35 studies, respectively. Of the eight studies at high risk of bias, three did not enroll a consecutive or random sample of patients, 26,27,37 three had > 10% of the source population that was not analyzed, 29,33,38 and two excluded patients in whom tests were of poor quality or without final diagnosis.…”

“…31,32 In two studies, insufficient data were reported to permit a judgment and the risk of bias was judged as "unclear." 28,35 Domain 2: index test. The risk of bias in the conduct or the interpretation of SPECT was judged as low, high, and unclear in eight, 26,27,[30][31][32][33][34]38 two, 28,29 and three [35][36][37] studies, respectively.…”

“…28,29 In three studies, the risk of bias was judged as "unclear" because insufficient data were reported to permit a judgment. [35][36][37] Domain 3: reference standard. The risk of bias in the conduct or the interpretation of the reference standard was judged as low, high, and unclear in two, 30,34 10, [26][27][28][29][31][32][33]35,36,38 and one 37 studies, respectively.…”

“…Of the 10 studies at high risk of bias, nine integrated the index test (ie, the V/Q SPECT result) into the reference standard. [27][28][29][31][32][33]35,36,38 In other words, the V/Q SPECT was used to determine whether or not patients had PE. This is a major bias leading to a high degree of uncertainty regarding the validity of the reference standard and an overestimation of the performances of the index test.…”