To report or not to report… prognostically relevant incidental chest CT findings

Abstract

Through the constantly increasing imaging quality and utilization of chest computed tomography (CT) are radiologists routinely confronted with incidental findings reflecting potential (preclinical) manifestations of cardiovascular disease (CVD), chronic obstructive pulmonary disease (COPD) and osteoporosis. However, the exact prognostic value of these incidental imaging findings and whether reporting of these findings will finally lead to patient benefit is not clear yet. This initiated the start of the PROgnostic Value of unrequested Information in Diagnostic Imaging (PROVIDI) study. PROVIDI is a retrospective multicenter cohort study comprising 23 443 subjects, aged ≥ 40 years who underwent routine clinical chest CT scanning between 2002 and 2005 for various diagnostic indications. We investigated whether certain incidental findings detected on diagnostic chest CTs contribute to the prediction of CVD and COPD. Incidental coronary artery calcifications, thoracic aorta calcifications, cardiac valve calcifications as well as cardiovascular diameter measurements were all significantly and independently related to future CVD events. Additionally, a simple CVD event risk score incorporating this information on cardiovascular features embedded in diagnostic chest CT, was developed and validated. This risk score was conceived from the perspective of the radiologists enabling accurate stratification of individuals into clinically relevant risk categories used in current CVD guidelines. Besides age and gender no other conventional risk factors were included in the risk score, since in general these patient characteristics are not available to the radiologist. Nevertheless, we would like to stress that extensive literature has clearly documented the uncertainty of risk scores based on conventional risk factors, because conventional risk factors are mere a surrogate for atherosclerosis. The CT based risk score as presented in this thesis is based on direct measures of atherosclerosis, providing a novel strategy and adequate estimation of CVD risk irrespective of the conventional risk factor status. Furthermore, morphologic correlates of COPD, such as emphysema and airway thickening, detected on CT scans obtained for other indications, demonstrated to be related to future hospitalization or death due to acute exacerbations of COPD. As for many people, however, information on these prognostically valuable metrics of CVD and COPD are 'freely' available since chest CT has developed into a very common imaging modality in the evaluation of (suspected) thoracic disease. With over 350.000 chest CTs performed annually in the Netherlands, diagnostic clinical CT scans offer a great opportunity to detect individuals at high-risk for CVD and COPD at an early stage, and hence better target these subjects for more tailored treatments based on incidental information embedded in routine diagnostic chest CTs in a clinical care population. This type of 'collateral information' obtained by chest CT can stimulate the start of prevention measures in subjects not recognized as high-risk by current risk algorithms. However, to state with confidence that utilization of incidental cardiovascular CT findings is cost-effective and effectuates improve in CVD outcome, a prospective randomized multicenter trial should be performed.