To our knowledge, this is the first study to describe the prevalence of radiologists reading CT screening studies in the United States from a nationally representative rather than targeted sample. This study revealed that one-third of a nationally representative sample of radiologists who read diagnostic CT studies of the chest, abdomen, and pelvis also read CT screening studies of the coronary arteries, lungs, and/or whole body. We found that the most commonly read study was CACS screening (26.7%), followed by lung cancer CT screening (19.2%) and whole-body CT screening (9.4%). These results are similar to unpublished data gathered by using the American College of Radiology’s 2003 Survey of Radiologists (20
), a stratified random sample survey of U.S. radiologists that revealed that 24% of diagnostic radiologists personally read lung screening CT studies and 13% read whole-body screening CT studies. Furthermore, while our data reflect the same relative prevalence of the different tests among screening centers that advertise on the Internet as reported by Illes et al (4
) and Kalish et al (5
), our study results suggest that CT screening is more prevalent than their estimates, probably because they identified only screening that was advertised on the Internet (4
The three CT screening examinations explored in this study—lung cancer screening CT, CACS screening, and whole-body CT screening—are at different stages of evidence and have different professional society recommendations. For example, CACS screening has the most conclusive research evidence of benefit (22
), and the American College of Cardiology has recently recommended CACS screening for patients with intermediate Framingham risk scores (24
). Evidence demonstrating a decreased disease-specific mortality from lung screening in smokers is still emerging and is intensely debated (18
). Results from the Early Lung Cancer Action Program study (18
) found that lung screening detects cancers at an earlier stage, while results from the National Lung Screening Trial (28
), which uses a randomized controlled design, are anticipated to provide stronger evidence about the impact of screening on population mortality. Professional societies do not advocate lung screening, but some have suggested it may be appropriate for individuals after a careful discussion with their physician regarding the risks, benefits, and uncertainties (29
Few data exist for the impact of whole-body screening. Results of one large case series (31
) showed that 32% of patients undergoing whole-body screening required follow-up of important findings, and results of one cost-effectiveness analysis (32
) suggest that it has minimal impact on population-based mortality at high cost. Professional societies uniformly discourage whole-body CT screening (8
), while several individuals have advocated the development of guidelines in response to the high rate of findings requiring follow-up (31
). For any emerging screening test, targeting screening at a population with high prevalence of the disease is necessary to avoid excessive false-positive rates. Emerging professional guidelines aim to guide individual risk assessment and define which patients should be included in high disease-prevalence groups.
Given the different stages of evidence and recommendations for these three screening examinations, we were not surprised to find radiologists more likely to believe CACS and lung CT screening appropriate as opposed to whole-body screening. Furthermore, screeners were significantly more likely than nonscreeners to favor screening in all scenarios. The favorable attitudes regarding heart and lung screening reported by most radiologists in this study may contribute to an environment that allows for the diffusion of CT screening into practice before conclusive empirical evidence and professional society endorsement. Furthermore, we were intrigued to find that whereas 70%– 80% cited physician or patient request of the examination as a reason for reading CT screening studies, only 40% cited patient benefit from the examination as a reason. It is also noteworthy that 30% reported “good business sense” and 19.2% reported “maximizing the use of our scanners” as reasons for screening.
As consultants who do not primarily manage patients’ care, the degree to which a radiologist’s screening practices are influenced by hospital or practice policy or by personal estimation of risk and benefit of the examination will vary. Nonetheless, radiologists are in a unique position regarding the diffusion of image-based screening tools. These findings raise questions about the extent of radiologists’ professional duties to educate and discuss the appropriateness of screening CT examinations with referring physicians and patients.
Most radiologists in this study believed that there should be endorsement from experts and professional societies, as well as evidence from observational studies and randomized controlled trials, before screening tests are offered to patients. Notably, we found no significant difference between screeners and nonscreeners in their demand for evidence. This may suggest differences among radiologists in the interpretation of existing evidence for screening or the degree to which evidence is the sole influence on their practice decisions. For example, the literature reveals sharp disagreement regarding whether current data are sufficient to support lung CT screening for smokers. It is possible that those who do and those who do not read lung CT screening studies in our study agree that there should be evidence from clinical trials, but disagree in their view of what counts as convincing evidence. It is also possible that all agree that trials are important, but disagree about whether trials are necessary before they will personally be willing to read studies.
Surveying a national, random sample of all practicing diagnostic radiologists allows for some generalizations about the differences in attitudes between those who do and those who do not read CT screening studies. The response rate of 41% limits generalizability; it remains unknown whether nonresponders were more or less likely to read CT screening studies or have different views about these examinations. While no response bias was found for characteristics we could test, it may exist for other factors. Furthermore, our study could not assess the rate of diffusion of CT screening, given its cross-sectional design. Since these data were collected in 2005, evidence, practices, and attitudes have evolved. Nevertheless, our data provide a baseline against which trends can be measured in the future. To obtain a reasonable response rate, it was necessary to limit the length of the survey questionnaire. Therefore, the depth in which individual issues were covered by our study was limited. For the same reason, we did not explore in detail screening examinations such as CT colonography and coronary CT angiography, which were not among the three most common examinations advertised at the time of our study. A further limitation involved social desirability bias; given the somewhat controversial nature of CT screening, respondents may have been hesitant to give their true opinions. We attempted to minimize this by emphasizing the confidential nature of this study. Because our questionnaire is new, its validity is limited, though we attempted to mitigate this with rigorous pilot testing. Finally, this study was focused on radiologists’ attitudes, but clearly an understanding of referring physicians’ practices and attitudes and patient experiences also are important (36
); the results of our study can contribute to future work that explores these perspectives.
As experts in imaging, radiologists should play a key role in whether and how CT screening examinations enter practice. Much of the confusion and controversy surrounding the provision of the three examinations studied will resolve as research continues to better quantify their utility. In light of the current uncertainty, however, we hope that the results from this study stimulate more discussion about when and under what circumstances providing new image-based screening tests to patients can be appropriate. Thinking through these issues now will aid our approach to new image-based screening tests that emerge in the future.