Following the implementation of single-photon emission computed tomography ventilation/perfusion (SPECT V/Q) in our department, we previously carried out an observational study over the period 2011–2013 that showed the safety of SPECT V/Q to rule out pulmonary embolism (PE). However, PE prevalence (28%) was high compared with some studies. Our hypothesis was that the use of SPECT V/Q may be responsible for an overdiagnosis of PE, especially at the implementation phase of the test. The aim was to carry out a time trend analysis of the evolution over the years of PE diagnosis with SPECT V/Q.
To evaluate the time trend of SPECT V/Q results, the conclusions of all SPECT V/Q scans performed for a suspected acute PE in our department from April 2011 to December 2016 were collected. To confirm the safety of a diagnostic management on the basis of SPECT V/Q to rule out PE, a retrospective observational study of the outcome of patients assessed with SPECT V/Q for suspected acute PE was carried out during the period 2014–2016. SPECT V/Q was interpreted using a diagnostic cutoff of one segmental or two subsegmental mismatches. The final diagnostic conclusion was established by the physician responsible for patient care. The safety of SPECT V/Q was assessed by monitoring the risk of thromboembolic events during the 3-month follow-up period in patients left untreated on the basis of a negative SPECT V/Q.
Over the period 2011–2016, an average 16% (95% confidence interval: 10–22%) annual reduction in the proportion of positive SPECT V/Q results was observed. The percentage of positive SPECT V/Q results was 25.3% over the period 2011–2013 compared with 16.3% in 2014–2016 (P<0.0001). Out of the 696 patients analyzed over the period 2014–2016, the SPECT V/Q was positive, indeterminate, and negative in 118, 3, and 575 patients, respectively. The 3-month thromboembolic risk in patients in whom PE was deemed absent according to the SPECT V/Q was 3/543=0.55% (95% confidence interval 0.19–1.61).
A continuous decrease in the annual proportion of positive SPECT V/Q results was mainly observed while maintaining the safety of the test to rule out PE. Explanatory factors include the introduction of a combined SPECT/CT scan, increased experience and familiarity with the test, and an increased awareness of the risks and consequences of overdiagnosing PE.
aDepartment of Nuclear Medecine
bDépartment of Internal Medicine and Chest Diseases, Brest University Hospital, EA3878 (GETBO), Brest, France
cDepartment of Medicine, Ottawa Hospital Research Institute at the University of Ottawa, Ottawa, Canada
Correspondence to Pierre-Yves Le Roux, MD, PhD, Service de Médecine Nucléaire, CHRU de Brest, 5 Avenue Foch, 29609 Brest Cedex, France Tel: +33 298 347 892; fax: +33 298 223 964; e-mail: email@example.com
Received November 23, 2018
Received in revised form January 17, 2019
Accepted January 20, 2019