Original ArticleIncidental Pulmonary Nodules Are Common on CT Coronary Angiogram and Have a Significant Cost Impact
Introduction
Incidental pulmonary findings are well described following imaging of the thorax for various indications including CT coronary angiograms (CTCAs). CTCAs are increasingly used for the investigation of low-moderate risk patients suspected of having coronary artery disease with a four-fold increase in studies performed from 2011 to 2015 [1], [2]. There is a substantial literature supporting the use of CTCA as a rule-out test due to its excellent diagnostic performance and cost-effectiveness [3], [4], [5]. However, studies suggesting CTCA may be a cost-effective screening strategy for the investigation of troponin negative patients with chest pain have not included downstream cost implications of extra-cardiac findings [6].
Incidental pulmonary nodules are the commonest extra-cardiac finding on CTCA ranging from 8 to 18%. The incidence of malignancy in such nodules is very low, and lesions are most frequently asymptomatic and clinically irrelevant [7]. While the 2005 Guidelines published by the Fleischner Society have been a standard for many years, the group has now published updated guidance with substantial new data on which to base the recommendations [8], [9]. These new guidelines will have the effect of reducing the total number of surveillance scans as compared to those from 2005, but even adherence to these guidelines may result in significant health care costs, thus impacting cost-effectiveness estimates for CTCA.
While scans acquire skin-to-skin data, some authors have suggested that reconstructing images to only include a Limited-Field-of-View (L-FOV) lung parenchyma within 1 cm of the heart, not only improves spatial resolution of the coronary arteries, but will also reduce the detection of incidental lung nodules [10]. This approach carries with it a number of medico-ethical as well as legal issues that have been previously debated [11], [12], [13], [14].
We sought to determine the prevalence of pulmonary nodules in patients undergoing CTCA in an Australian tertiary care hospital, to characterise the population effected, and to determine the cost burden resulting from these incidental findings. In addition, we have evaluated the economic impact of routine use of L-FOV rather than Full-FOV.
Section snippets
Study Setting
This cohort comprised consecutive CTCAs performed in the calendar year 2012 at a tertiary care referral hospital in Melbourne, Australia. The scans were retrospectively identified from the imaging department database by manual review of reports. Subjects were excluded if they were under the age of 35, had no data recorded from the examination, or had known malignancy or other pulmonary findings identified prior to CTCA. The study was approved by the local Human Research Ethics Committee.
Data Collection
Results
For the calendar year 2012, 2539 CTCAs were performed for the investigation of suspected coronary artery disease, with 2479 meeting inclusion and no exclusion criteria. The cohort showed a slight male predominance (51.5%) with a median age of 59 (IQR 51–68). 345 (13.9%) subjects had nodules identified at the time of CT scanning on full-field imaging. Of those with nodules, 129 were found to have a single nodule, with the remaining 216 (63%) having multiple nodules. Patient demographics are
Discussion
This study is the first to characterise incidental pulmonary nodules in an Australian population undertaking CTCA. We show a prevalence of pulmonary nodules of 14% with no significant difference when stratified for sex or smoking status. The nodules were predominantly <6 mm, with a lower lobe predominance. Based on Fleischner criteria we also demonstrate a projected additional conservative cost of $63.62 per patient for follow-up CT imaging, which is approximately 10% of the schedule fee for
Conclusions
Indeterminate pulmonary nodules are a common incidental finding on CTCA and prevalence appears to be independent of smoking status. The majority of the nodules are small with only a minority of imaged nodules identified in the partially imaged upper lobes, where risk of lung cancer is highest. These incidental pulmonary nodules present a significant cost burden. Use of Limited FOV markedly reduces the number of incidental nodules identified, and consequently the cost burden of CTCA, but this
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