Replacing Conventional Chest X-Ray Imaging with Ultra-low-dose CT: The REPLAiCE Study

The Chest X-Ray (CXR) is the standard imaging tool applied in the diagnostic
work-up in patients suspected of pulmonary pathology. In recent years, advances
in CT scanner hardware and reconstruction techniques have enabled the
introduction of ultra-low-dose CT (ULCDT) scans, which can be acquired at a
similar radiation exposure to the patient as a conventional CXR exam. Increases
in diagnostic accuracy and radiologist confidence when directly comparing ULDCT
to CXR have been shown in numerous studies in the detection of lung nodules,
pneumonia, pneumothorax, and the assessment of trauma.

Yet, in larger studies these results have not been conclusive, have focused
only on patients presenting in the emergency department, and had limited to no
attention for the diagnostic follow-up. The REPLAiCE study is a randomised
trial designed to evaluate the potential of replacing the CXR with an ULDCT in
general outpatient referrals. Our hypothesis is that we can show
non-inferiority for ULDCT compared to chest x-Rays in our patient population.

The primary objective of the study is to investigate the medium to long term
effects of replacing the conventional CXR exam with an ultra-low-dose CT in
terms of patient health.

Secondary outcomes are measures are
• Quantity and type of follow-up imaging, assessed using the electronic patient
records
• Mental health, which is assessed by the mental health summary scale of the
SF-12
• Length of hospital stay, expressed in days and extracted from electronic
patient records
• Mortality within one year, extracted from electronic patient records
• Percentage of normal (i.e., absence of disease) compared to abnormal scan
reports, extracted from electronic patient records
• Time to diagnosis (where applicable), defined as the time between
presentation in the hospital and a definitive diagnostic formulated by the
referring physician
• Time to treatment (where applicable), defined as the time between
presentation and the start of a treatment
• Number of patients in follow-up due to incidental findings, extracted from
electronic patient records
• Patient satisfaction and experience with participation, as assessed through
the Generic Short Patient Experiences Questionnaire
• Referring physician experience, assessed through questionnaires

REPLAiCE is a single-center non-inferiority randomized controlled trail (RCT)
comparing ultra-low-dose chest CT scans to chest X-Rays in consecutive
outpatients presenting in the hospital for imaging for suspected non-traumatic
pulmonary disease.

Participants are approached for inclusion in the study using the order of their
presentation in the hospital to respect minimum time intervals between
consecutive participants. Upon participation the imaging strategy for a
participant is randomized where either conventional chest X-Ray imaging or
chest ULDCT scan will be used. To account for seasonal effects inclusion will
proceed for a period of at least 1 year.

Information regarding the impact of diagnostic imaging on patient outcome is
generally considered as more substantial evidence when compared to diagnostic
accuracy alone. In our approach we aim to provide quicker treatments by
achieving a more accurate diagnosis more quickly. Accordingly, we expect the
use of ULDCT to be superior to the use of CXR in chest imaging used as work-up
of patients suspected of non-traumatic pulmonary disease.

Participation in this study does not place additional risks or burdens on
participants. After randomisation patients may, instead of undergoing a Chest
X-Ray, undergo an ultra-low-dose CT scan. The radiation exposure of both
examinations is nearly equal (0.1 mSv vs 0.05 mSv) and does not constitute an
additional risk of the ULDCT group over the CXR group