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Original Research |
1 Research Department, American College of Radiology, 1891 Preston White Dr.,
Reston, VA 20191.
2 Department of Diagnostic Radiology, Yale University, New Haven, CT.
Received February 11, 2005;
accepted after revision February 16, 2005.
Address correspondence to J. H. Sunshine.
Abstract
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MATERIALS AND METHODS. We tabulated data from the American College of Radiology's 2003 Survey of Radiologists, a stratified random-sample survey that oversampled interventionalists and achieved a 63% response rate with a total of 1,924 responses. Responses were weighted to make them representative of all radiologists in the United States. We compared information about interventionalists with that for other radiologists.
RESULTS. Depending on the definition of who is an interventionalist, 8.5–11.5% of radiologists are interventionalists. By most definitions, only slightly under half of interventionalists spend 70% or more of their clinical work time performing interventional procedures. Interventionalists work, on average, 56–58 hr weekly, a few hours longer than other radiologists. The average interventionalist performs procedures in five of the seven categories of procedures into which we divided interventional radiology, compared with one or two categories for other radiologists. The average interventionalist performs procedures in five of the seven broad categories (such as MRI, CT, and nuclear medicine) into which we divided all of radiology, much the same breadth of practice as other subspecialists and also as nonsubspecialists.
CONCLUSION. Interventionalists have become a sizable group within radiology. They are in some ways like other radiologists and in other ways different, but they do not spend as much of their time in their subspecialty as some assume and, overall, are not as different.
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The ACR, as part of its mission of providing important and useful information to the professions it serves, periodically conducts large-scale, multitopic surveys of the members of these professions and the practices in which they work [1–16]. In response to the growing importance of interventional radiology and the action at the 2001 ACR annual meeting, the ACR's 2003 Survey of Radiologists was designed with a special focus on interventional radiologists. (The 2003 Survey of Radiologists, together with the companion 2003 Survey of Radiation Oncologists, were the first large-scale ACR surveys after the 2001 annual meeting.) The 2003 Survey's special focus on interventional radiologists consisted of a double-sized sample of interventional radiologists and a design that included more ways of recognizing and defining interventional radiologists than for any other field within radiology. As well, this article, an in-depth portrait of interventional radiologists, is the first full-scale article to be produced from the 2003 Survey.
To the best of our knowledge, this is the first comprehensive portrait of interventionalists based on a statistically representative sample drawn from all radiologists in the United States. A 2000–2001 survey by the Society of Cardiovascular and Interventional Radiology (now the Society of Interventional Radiology [SIR]) contains a great deal of valuable information [17], but is focused on the practices in which interventionalists work more than on the interventionalists themselves. Moreover, it is based on SIR membership, meaning it is not as representative as our survey, which includes interventionalists who are not SIR members.
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The questionnaire for the 2003 Survey consisted of 36 items; many items in turn contained multiple subitems. Questionnaire items and topics were elicited from two rounds of canvassing ACR physician and staff leaders, winnowed according to priorities indicated by top leadership, and pretested in two large pretests conducted in autumn 2002, with refinements made after each pretest.
The survey sample, a stratified random sample composed of four strata, was taken primarily from the American Medical Association's (AMA) Physician Masterfile, a reasonably complete listing of all allopathic physicians in the United States, whether AMA members or not, but also included a sample of osteopathic radiologists obtained from the American Osteopathic College of Radiology. The sample included residents, fellows, and retirees, not merely posttraining professionally active physicians.
The survey was administered by our contractor by mail between March and August 2003, with nonrespondents sent up to four remailings as necessary, and other steps were taken to boost the response rate. The response rate achieved was 63%, with 1,924 usable responses.
Responses were weighted so that the weighted statistics would be representative of the answers that would have been received if all physicians in the United States in the four strata had been surveyed and had responded. First, logistic regression was applied separately to each of the four strata to ascertain if there was a statistically significant difference in response rate by sex; age; census region; whether the physician was an ACR member; or, for the "all other radiologists" stratum, whether the radiologist was listed in the AMA Masterfile as a subspecialist. Second, within each stratum, respondents were divided into substrata on the basis of any factors found significant in the logistic regressions, and substrata (or the entire stratum, if there were no substrata) were weighted separately, each by the reciprocal of its response rate. Third, these weights were multiplied by the reciprocal of the stratum's sampling rate.
Our leading tool to minimize data deficiencies was the designation of the 12 items on the questionnaire judged most crucial as "core questions." When questionnaires were returned, our contractor checked that these 12 items were indeed answered and made three designated consistency checks involving them. If there were any problems with the core items, the contractor telephoned the respondent to obtain the missing response or responses or to resolve the consistency problems. Data used in this report have been, in addition, cleaned and edited to further minimize deficiencies.
Definition of Variables
The definition of most variables is obvious from the Results section and
Tables 1,
2,
3,
4,
5,
6,
7,
8. We detail here only the
definitions of interventionalists that we used; definitions of other variables
are detailed in the AJR electronic supplement.
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To provide the fullest picture of interventionalists, this article contains information on a large number of different definitions of who is an interventionalist. The definitions are as follows:
Analysis Methods
All information presented in the remainder of this article, unless
otherwise noted, is based on weighted data and refers to physicians from all
four strata combined. Where numbers of physicians are given
(Table 1), an adjustment was
made for item nonresponse—that is, for the failure of a limited
percentage of respondents to answer each question—so that the numbers
are, as always, representative of what answers would have been if all
physicians of interest in the country had responded.
Reported SEs and tests of statistical significance are calculated taking
into account not only the weighted nature of the data but also the complex
survey design—that is, the fact that responses come from distinct
strata. The SEs are calculated with the Statistical Analysis System (SAS)
software procedure called "Surveymeans." All data analysis was
conducted with SAS software, release 9.0 (SAS Institute). Because most
comparisons are made between interventionalists and five different comparison
groups of radiologists (Tables
3,
4,
5,
6,
7,
8), in keeping with the
Bonferroni inequality [20], we
use a two-tailed z test with 0.01 or less as the criterion of statistical
significance rather than the more common 0.05 or less. The SEs for the
percentages in the tables can be approximated by the following formula:
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Table 2 shows the relationship between pairs of characteristics of interventional radiologists. Each row of the table refers to those radiologists with the characteristic listed at the left of the row, and each cell tells what percentage of these radiologists also have the characteristic listed at the top of the column in which the cell appears. For example, the table shows, in its second row of data, that of the radiologists who have a CAQ in vascular and interventional radiology, approximately one third are listed in the AMA Masterfile as interventionalists, approximately two thirds did a fellowship in the field, a similar portion listed interventional radiology as their primary specialty on the ACR's 2003 Survey, three quarters spend 30% or more of their clinical work time performing interventional procedures, and nearly half spend 70% or more of their clinical work time in the field.
Other highlights of the table include the finding that one eighth of those who did an interventional and/or vascular fellowship indicate they do not currently perform any procedures in the field. Of those who reported on the ACR's 2003 Survey that interventional radiology is their primary specialty, somewhat over half have a CAQ, almost three fourths did a fellowship in the field, four fifths spend 30% or more of their clinical work time performing interventional procedures, and more than two fifths spend 70% or more of their clinical work time in the field. By most definitions of who is an interventionalist, only a minority of interventionalists spend 70% or more of their clinical work time performing interventional procedures (Table 2, next to last column).
Tables 3 and S1 present demographic characteristics of interventional radiologists and the corresponding demographics of five comparison groups of radiologists. (Tables S1–S11 are found in the AJR electronic supplement, available at www.ajronline.org, to this article and present more detail than the tables printed here.) Almost regardless of how interventionalists are defined, they are, on average, in their mid to late 40s in age, a few years younger than radiologists overall, who average 51 years old, and also a few years younger than other subspecialists, who average 50.
By any definition of who is an interventionalist, the percentage of interventionalists who are women, 6% at most, is far lower than the percentage of all radiologists who are women, 18%, and is far lower than the percentage of all subspecialty radiologists who are women (19–24% depending on the criterion used to identify subspecialists).
Interventionalists do not differ in any important way from the comparison groups in the percentage who report they are certified by the American Board of Radiology (ABR) (> 95%) or in their distribution among the four census regions (over one fourth in the South, under one fourth in the West, and approximately one fourth each in the Northeast and Midwest).
Types of Procedures Performed by Interventionalists
By almost any definition of who is an interventionalist, approximately 90%
or more of interventionalists perform interventional procedures in the
extremities, renal interventional procedures, abdominal interventional
procedures, and pelvic interventional procedures (Tables
4 and S2). In contrast, only
10–20% of subspecialists who are not interventionalists perform each of
these types of procedures, and approximately 25–30% of radiologists who
are not subspecialists do so. The percentages of interventionalists who
perform head and neck interventional procedures (70–80% by most
definitions of who is an interventionalist) or spinal interventional
procedures (60–70%) are lower. Only 10–20% of interventionalists
perform cardiac interventional procedures, but the proportion is much lower,
approximately 3%, among other radiologists. Of these seven types of
interventional procedures, the average interventionalist performs
approximately five while the average noninterventionalist performs one or
two.
Neurointerventionalists show a different pattern: Approximately 90% of them perform head and neck interventional procedures and spinal interventional procedures. However, fewer than 10% of them perform each of the other types of interventional procedures. This is, if anything, less than the corresponding percentage for noninterventionalists.
Tables 4 and S3 divide the full range of procedures performed by radiologists into seven major categories, such as nuclear medicine, MR, CT, and interventional. Interventionalists in general perform an average of approximately five of the seven general categories of procedures, which is about the same as radiologists overall. The exceptions are that those interventionalists who spend at least 70% of their clinical work time performing interventional procedures on average perform only 3.5 of the seven categories of procedures and neurointerventionalists average 3.2 categories.
Of course, interventionalists are far more likely to perform interventional procedures than other radiologists. Only a third of subspecialists who are not interventionalists and two fifths of radiologists who do not subspecialize perform any interventional procedures. However, apart from this, Table S3 shows relatively few major differences between interventionalists and other radiologists in the percentages performing each of the seven major categories of procedures.
Other Aspects of the Work of Interventionalists
On average, full-time interventionalists report working approximately
56–58 hr in a typical full week, whereas other radiologists average
approximately 52 hr per week (Tables
5 and S4). For
interventionalists, the 25th percentile of weekly hours is 50 and the 75th
percentile is 60 (Table S4). Twenty percent of all radiologists work
part-time, and the percentage for noninterventional subspecialists is the
same, whereas only 6% or fewer of interventionalists are part-timers (Tables
5 and S4).
However, there is no pattern of a difference in vacation days between full-time interventionalists and other full-time radiologists; all average approximately 35 vacation days annually. For interventionalists, the 25th percentile is approximately 20 vacation days and the 75th percentile is 50 days (Table S4). There is no difference in annual days for continuing education and professional society meetings among full-timers; all average approximately 10 days (Tables 5 and S4). Interventionalists are also similar to radiologists overall in working at an average of approximately three distinct locations, with roughly half working at one or two locations and approximately one third working at four or more locations (Table S4).
Also like radiologists overall, approximately 15% of interventionalists would like less work, even though that meant their income would decrease proportionately, and a somewhat greater percentage would like more work with a corresponding increase in income (Tables 5 and S5). Finally, interventionalists are like radiologists overall in reporting, on average, a level of enjoyment of their work approximately halfway between "enjoy very much" and "enjoy somewhat."
Virtually all interventionalists report spending at least part of their work time in clinical practice at hospitals (Tables 6 and S6). In contrast, just under 90% of other radiologists do so. Moreover, among interventionalists who are involved in clinical practice in hospitals, the average percent of work time spent at it is approximately 85%, while among noninterventionalist specialists, the corresponding average is 70%. The converse of these differences is found in clinical work at nonhospital sites. Another difference is that approximately 40% of noninterventionalist subspecialists spend some time teaching, whereas only approximately one fourth of interventionalists do.
The Practices in Which Interventionalists Work
By most definitions of who is an interventionalist, 9–15% of
interventionalists work in primarily academic practices (Tables
7 and S7). This is below the
25% for noninterventionalist subspecialists but is above the 6% statistic for
nonsubspecialists. The main exception to the pattern consists of radiologists
who spend 70% or more of their clinical work time doing interventional
radiology; 27% of them are in academic practices. In general, 50–60% of
interventionalists are in private (single-specialty) radiology practices,
which is higher than the percentages for other radiologists. In contrast, by
almost all definitions, fewer than 1% of interventionalists are in solo
practice, and the corresponding statistics are 3% for other subspecialists and
9% for those who do not subspecialize.
By most definitions of who is an interventionalist, 24–34% of interventionalists work in practices primarily located in the main city of a large metropolitan area, which is defined as an area with a population of more than 1 million (Tables 7 and S8). For some definitions of interventionalist, this is, by a statistically significant amount, above the 18% figure for radiologists not subspecialized or below the 38% for other subspecialists. Again, those who spend 70% or more of their clinical time doing interventional work are an exception; 41% are in this type of location.
Some 30–40% of interventionalists work in practices that serve only hospitals, which is higher than the 22% for other subspecialists (Tables 7 and S9). On average, the practices in which interventionalists work provide approximately five and a half of the six major categories of noninterventional procedures on which we obtained data (Tables 8 and S10). (Tables 8 and S10 deal with the procedures provided by the entire practice in which interventionalists work. Tables 4 and S3 deal with the procedures personally performed by each individual interventionalist him- or herself.) This average of approximately five and a half is very much like comparison categories of radiologists, and the similarity holds not only for the total number of major categories of procedures, but also for each one of the six major categories. Table S10 illustrates this for a relatively low-tech category of procedure, plain films and fluoroscopy, and for a high-tech procedure category, MRI.
By most definitions of who is an interventionalist, interventionalists work in practices with an average size of 15–20 members (Tables 8 and S11). This is smaller than the average of 24 for other subspecialists, but is larger than the average of 12 for nonsubspecialists. The 25th percentile practice size for interventionalists is seven or eight and the 75th percentile is mostly in the 20–30 range, depending on definition (Table S11). Although their practices are not on average as large as those of other subspecialists, in general, 82% or more of interventionalists have coverage from a member of their group who is in the same specialty when they are away, compared with 70% for noninterventionalist subspecialists (Tables 8 and S11).
By most definitions, approximately 70–80% of interventionalists are in practices entirely owned by members of the practice. This is above the percentage for some comparison categories.
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Many of the SIR survey's [17] estimates are similar to those of this survey. These include varied items such as the percentage of interventionalists in academic practices and in other types of practices, the fraction of time interventionalists spend performing interventional procedures, and annual days for education and professional meetings. However, the SIR survey found more vacation days for full-timers than our survey did (a mean of 43 vs 35 days) and shorter weekly hours (50 vs 55 hr). These differences may reflect an increasing workload between 2000 and 2001, when the SIR survey was conducted, and the 2003 date of our survey [18, 21]; the restriction of the SIR survey to SIR members; sampling variability (the SIR survey does not report SEs); and/or other causes.
Substantive Findings
A number of ways of defining who is an interventional radiologist indicate
that 8.5–11.5% of radiologists, or approximately 2,300–3,100
radiologists, are interventionalists. It is, however, important to note that
only 6% of radiologists spend 70% or more of their clinical work time
performing interventional procedures. Thus, there are far fewer full-time
interventionalists or even radiologists who spend a majority of their time
doing interventional procedures than there are radiologists who subspecialize
in interventional radiology but are not subspecialized to that extent.
These findings have important implications for one of interventional radiology's major socioeconomic concerns—namely, the competition among interventionalists, cardiologists, vascular surgeons, and others for interventional work. The fact that more radiologists are subspecialized in the interventional field than are doing interventional radiology full-time (or nearly so) means there are more radiologists and more radiology groups who can compete for this work than would be the case if only full-time interventionalists (or those nearly full-time) were doing it. This enhanced on-the-ground presence should help in the competition. On the other hand, to the extent that success in obtaining patients is aided by having offices for patient visits, as cardiologists and surgeons do, radiology practices may be less likely to provide this resource if their interventionalists do not work full-time at interventional radiology.
The fact that most interventionalists spend a substantial fraction of their time at other activities provides a cushion, whatever the outcome of the competition. If the interventional work of radiologists expands, these individuals can cut back their noninterventional work to take on the additional interventional work, and vice versa.
Interventionalists are much concerned that, each year, a considerable fraction of interventional fellowships go unfilled. Our impression is that the same is true in a number of other subspecialty fields and that the reason, overall, is that the total (across all subspecialties) of fellowship positions offered exceeds the number of graduating residents who want fellowships. Be that as it may, our data again illuminate this issue. Our findings about how many interventionalists seek less work and how many seek more work (Tables 5 and S5) indicate there is not currently a shortage of interventionalists. The cushion described in the preceding paragraph will help to ensure that a shortage does not develop in the future. On the other hand, the findings from Table 2 that, first, a fifth of radiologists who spend 50% or more of their clinical work time performing interventional procedures did not have an interventional fellowship and, second, that two fifths do not have the interventional CAQ suggest there may be a quality-of-care problem associated with the failure to fill more interventional fellowships.
Our findings also illuminate an issue in the staffing of radiology groups. With interventionalists overwhelmingly having separate call (night and weekend coverage arrangements) (Tables 8 and S11), with a minimum of two and preferably three physicians necessary to have a reasonable call and vacation coverage schedule, and with interventionalists very roughly 10% of all radiologists, it would seem that a group needs a minimum size of 20 or 30 members for its interventional component to function comfortably. This consideration is presumably an important factor in the continuing increase in the percentage of radiologists who are in large groups [8].
Because interventional radiology is relatively new as a major field in radiology, it is not surprising that interventionalists are, on average, younger than radiologists in general or than other subspecialists. On reflection, it is even not surprising that one eighth of those who did an interventional fellowship currently do not perform interventional procedures. A radiologist may have taken a fellowship 20 or more years ago, and some radiologists change the focus of their careers over time spans that long.
It is surprising—and somewhat disturbing—that so few interventionalists are women. The percentage of women among interventionalists is far lower than among radiologists in general, and radiology overall already has a disproportionately low number of women. It would be desirable that women, who currently constitute about half of all U.S. medical students, be more than a few percent of the physicians in this important and new field in radiology.
Also surprising is that interventionalists on average perform procedures in so many of the broad categories of radiology—five of seven. This is, however, similar to the pattern for noninterventional subspecialists and is also as broad a range of practice as the average radiologist who does not subspecialize.
There are a number of nonclinical ways in which interventionalists are intermediate between other subspecialists and nonsubspecialists. For example, interventionalists to some extent are less concentrated in the main cities of large metropolitan areas and are present in more nonmetropolitan areas than other subspecialists, but interventionalists are more concentrated in main cities of large metropolitan areas than nonsubspecialists. Similarly, interventionalists are less likely to be in academic practices than other subspecialists, but they are more likely to be academics than nonsubspecialists are.
In a number of respects, radiologists who spend 70% or more of their clinical work time performing interventional procedures—who, as noted, are only about half or fewer of interventionalists—are different from other interventionalists and differ from these patterns. Those who spend 70% or more of their clinical work time performing interventional procedures are more likely to be in academic practices than other interventionalists; are more concentrated in the main cities of large metropolitan areas; and perform, on average, fewer types of noninterventional procedures.
Neurointerventionalists form an even more distinct group. Despite their training in interventional techniques, they are less likely than noninterventionalists to perform interventional procedures other than neurointerventional ones. Apparently, they are very closely tied to neuroradiology, and this tie is so strong that it reduces activity in other interventional areas.
Study Strengths and Limitations
Like other studies, ours has both strengths and limitations. Major
strengths include the fact that the data are from a large, carefully conducted
survey that achieved a high response rate through intensive follow-up.
Weighting adjusted for nonresponse bias—that is, differences between
respondents and nonrespondents—in the characteristics used in the
weighting (age and ACR membership), and logistic regression analysis showed
there was no significant nonresponse bias in terms of sex and region. Paying
careful attention to the completeness of our sample, we included osteopathic
radiologists, who are approximately 3% of all radiologists, and nuclear
medicine specialists with a major connection to radiology. Multiple steps
improved data quality.
The survey nonetheless has noteworthy limitations. As with almost any survey, statistics drawn from it may have inaccuracies from at least three sources: sampling variability (the likely size of these inaccuracies is measured by the SE); nonresponse bias (but only with respect to characteristics not considered in the weighting or logistic regressions); and incorrect or illogical responses (some still remain despite careful and extensive data cleaning).
Also, as with any survey, aspects of the questions on our survey affect the answers given and, hence, the findings. One major example is the question about how respondents divide their clinical work time among radiology fields. This question included as answer options both technique-defined fields, such as interventional radiology, and fields defined by organ system or body part, such as breast imaging. Respondents were instructed that the reported percentages should total 100. If there had been one question for techniques and another for organ systems, with directions that each was to total to 100%, then the number of radiologists reporting time spent in any field and the reported amounts of time spent would have been larger. In particular, the fraction of radiologists reporting they spend some percentage of time in interventional radiology is only about half as large as the fraction (45%) who check off some type of interventional procedure as something they perform. We think this problem has relatively little effect on estimates of those who spend a relatively large amount of time—say, 30% or more—in a field.
In conclusion, our detailed portrait of interventionalists shows that they are in some ways like radiologists overall and in other respects are different. By most definitions of who is an interventionalist, more than half of interventionalists do not spend a large majority of their time performing interventional procedures. Together, these findings suggest that interventional radiologists are less different from other radiologists than is sometimes supposed.
Acknowledgments
We thank all those who responded to the 2003 Survey of Radiologists. By
contributing the time needed to complete the questionnaire, they have helped
make important information available to the entire profession.
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