Rationale and Objectives
The Hirsch Index (H index) is widely applied as a metric of scientific productivity. The purpose of this study was to evaluate the role of self-citation on the H index in academic radiology.
Materials and Methods
Through the National Resident Matching Program’s Web site, one third (47/139) of radiology residency programs were selected randomly. All chairpersons and full professors were included. Using the Scopus database, we calculated the H index as well as the number of cumulative citations with and without inclusion of self-citations. We determined the proportion of academic staff in which H index increased by one, two, or greater than two integers. We also correlated the proportional increase in H index before and after inclusion of self citations with the number of publications.
Results
A total of 487 academic staff (47 chair and 440 professors) was identified. Because of self-citation, mean ± SD of the H index increased from 13.7 ± 9.9 to 14.0 ± 10.2; mean ± SD of cumulative citations increased from 1804 ± 1889 to 1870 ± 1971. H index numbers did not change in 376/487 (77%) authors as a result of self-citation. There was no correlation between number of publications and proportional change of H index.
Conclusion
The effect of self-citation is minimal in academic radiology, as evidenced by the fact that cumulative citations increase by only 2% and the large majority of H index values do not change by even a single integer after inclusion of self-citation.
Hirsch index (H index) was invented to measure scientific output of faculty members . The H index combines number of publications and citations to an author to evaluate scientific impact of the given author on the literature. Traditional academic productivity models focus on number of publications, citations, journal impact factor, order of authorship, and so on, individually. Among different databases that calculate H index automatically, Scopus, Google scholar and Web of science are used more commonly. Given that H index has been widely accepted by authors and institutes as a proper surrogate for conventional methods, self-citations and database accuracy are variables that can affect it. Previous authors have proposed that self-citation represents an important limitation of the H index . However, the exact impact of such citation, to our knowledge, has not been previously studied in the field of radiology . To our knowledge, there is no publication available in the field of Radiology to evaluate the impact of self-citation on increasing H index. The purpose of this study was to evaluate the role of self-citation on the H index in Academic Radiology.
Method and materials
Inclusion of Programs and Faculties
In a previous publication by our group , in October and November 2009 through the National Resident Matching Program’s web site ( http://www.nrmp.org ), we identified 139 academic radiology centers that were training residents in the year 2009. One third of programs ( n = 47) were randomly included. Through programs’ web pages, faculty members were identified and all chairs and full professors were included. Clinical staff with MD (or any equivalent degree), MD/PhD, and MD/MPH degrees were included. The reviewer directly contacted the department’s chair or residency program director to obtain the list of faculty members for four centers that were not available in the programs’ web pages. Random selection of programs was performed using a random number generator in Microsoft Excel (Microsoft Corporation, Redmond, WA).
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Impact of Self-citation on the H Index
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Statistical Analysis
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Results
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Table 1
Effect of Self-citations in Chairmen and Professors
Citations, Mean (SD) Cited Publications, Mean (SD) Self-citation excluded Individual Cumulative, self-citation included Cumulative, self-citation excluded 13.3 (9.7) 1460 (1468) 1795 (1915) 1744 (1865) 82 (68) 13.7 (9.9) 1477 (1388) 1878 (1987) 1811 (1894) 95 (75)
Table 2
Stratification of Different Groups of Authors Based on H Index Increase after Self-citation
Number (% of All) Cited Publications, Mean (Median; Range) H Index Including Self-citation, Mean (Median; Range) Proportional Increase in H Index from Self-citation by Percent, Mean (Median; Range) Individual Citations, Mean (SD) Proportional Increase in Cumulative Citation from Self-citation by Percent, Mean (Median; Range) H index did not change 376 (77%) 78 (59; 1–455) 11.3 (9; 1–44) 0 1201 (1171) 2% (0.1%; 0%–74%) H index increased 1 unit 77 (16%) 131 (126; 2–370) 20.8 (21; 2–51) 7% (5%; 2%-50%) 2266 (1622) 4% (3%; 0%–40%) H index increased 2 unit 28 (6%) 183 (182; 53–446) 29.5 (30; 7–52) 9% (7%; 4%-29%) 2945 (1846) 9% (8%; 3%– 27%) H index increased 3 unit 6 (1%) 157 (168; 108–183) 21.8 (19; 13–36) 15% (14%; 8%–23% 1663 (702) 14% (12%; 7%–35%)
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Discussion
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Conclusion
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References
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3. Rad A.E., Brinjikji W., Cloft H.J., et. al.: The H-index in academic radiology. Acad Radiol 2010; 17: pp. 817-821. Epub 2010 May 15
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