A bibliometric analysis of highly cited publications in Web of Science category of emergency medicine

3.1 Document type and language of publication

A total of 1,026 highly cited publications (0.95% of 107,437 documents in the category of emergency medicine in SCI-EXPANDED) with TC${}_{\mathrm{2019}}$$\ge$ 100 were found including 898 highly cited articles (0.95% of 68,694 articles). It was reported that the percentage of highly cited documents was 0.68% in the category of health care sciences and services [6], and the percentage of highly cited articles in the category of dentistry, oral surgery and medicine was 1.8% [9]. To have scientific results, which can be repeated and checked, Ho’s group proposed citation indicator TC${}_{\mathrm{year}}$, the number of citations from Web of Science Core Collection since publication year to the end of the most recent year [11, 12] and citations per publication (CPP${}_{\mathrm{year}}$ = TC${}_{\mathrm{year}}$/TP) [14]. Analysis of document types and their citations per publication was proposed earlier [17]. Table 1 shows the characteristics of the five document types with the total number of publications (TP), the number of authors per publication (APP), and citations per publication (CPP${}_{2019}$) [18]. Document type of articles was the most popular with 898 articles (88% of 1,026 highly cited documents) and the number of authors per publication (APP) of 5.5. Reviews had the highest CPP${}_{2019}$ with 181, which is slightly higher than articles with CPP${}_{2019}$ of 166. In total, 113 highly cited reviews were published in 12 journals, mainly in Annals of Emergency Medicine (31 reviews; 27% of 113 reviews) with CPP${}_{2019}$ of 171, Resuscitation (24; 21%) with CPP${}_{2019}$ of 209, and Injury-International Journal of the Care of the Injured (24; 21%) with CPP${}_{2019}$ of 229. The most frequently cited review entitled ‘Epidemiology of adult fractures: A review’ [19] was published in Injury-International Journal of the Care of the Injured with TC${}_{2019}$ of 894. It has been noticed that documents could be classified within two document types in Web of Science, resulting in the sum of percentages greater than 100% [20]. For example, 136 documents were classified in both document types of articles and proceedings papers.

Only document type of articles was considered for further analysis because they include more complete information such as introduction, method, results, discussion, and conclusions [21]. As a result, 898 highly cited articles were identified in the Web of Science category of emergency medicine in SCI-EXPANDED. Only eight non-English highly cited articles were published in German. All the eight articles were published in Unfallchirurg with CPP${}_{2019}$ of 133.

3.2 Publication distribution

A relationship between the total number of highly cited articles in a year (TP) and their citations per publication (CPP${}_{\mathrm{year}}$ = TC${}_{\mathrm{year}}$/TP) by the decades [5] and the years [22] in a Web of Science category in SCI-EXPANDED has been proposed. Altogether, 898 highly cited articles in emergency medicine were found between 1966 and 2016 with total TC${}_{2019}$ of 148,828 with an average of 166 and the maximum value of TC${}_{2019}$ was 1,062. Fig. 1 shows the distribution of these 898 highly cited articles over the years and their citations per publication (CPP${}_{2019}$). Only two highly cited articles were found in 1966 and no articles were identified after 2016. The year 2007 was the most prolific in terms of highly cited articles in emergency medicine. The highest CPP${}_{2019}$ of 349 in 1970, which can be attributed to the only highly cited article entitled ‘Acute arterial injuries in Vietnam: 1,000 cases’ [23] in the Journal of Trauma with TC${}_{2019}$ of 349. The earliest highly cited articles in emergency medicine were ‘Bullet velocity and design as determinants of wounding capability: An experimental study’ [24] and ‘Tolerance curves of acceleration and intracranial pressure and protective index in experimental head injury’ [25] published in Journal of Trauma in 1966 with TC${}_{2019}$ of 107 (ranked 747${}^{\mathrm{th}}$) and 106 (ranked 770${}^{\mathrm{th}}$), respectively. The latest highly cited articles were found in 2016, entitled ‘EuReCa ONE-27 Nations, ONE Europe, ONE Registry A prospective one month analysis of out-of-hospital cardiac arrest outcomes in 27 countries in Europe’ [26] in Resuscitation and ‘Multicenter evaluation of a 0-hour/1-hour algorithm in the diagnosis of myocardial infarction with high-sensitivity cardiac troponin T’ [27] in Annals of Emergency Medicine with TC${}_{2019}$ of 200 (ranked 160${}^{\mathrm{th}}$) and 135 (ranked 415${}^{\mathrm{th}}$), respectively.

Fig. 1.Number of highly cited articles and citations per publication by year.

3.3 Journals

A total of 31 journals were classified under the Web of Science category of emergency medicine in 2019. The 898 highly cited articles were published in 14 of these journals (45% of 31 journals), and in four other emergency medicine journals that were no longer tracked by the Web of Science category of emergency medicine as of 2019 (Table 2). Eighty-five percent of the highly cited articles were published in four journals: Annals of Emergency Medicine (340 articles; 38% od 898 articles), Resuscitation (176; 20%), Academic Emergency Medicine (138; 15%), and Injury-International Journal of the Care of the Injured (104; 12%). Annals of Emergency Medicine not only published the most highly cited articles but also had the highest IF${}_{2019}$ of 5.799 in the category of emergency medicine. Scandinavian Journal of Trauma Resuscitation & Emergency Medicine had the highest APP of 8.0, followed by Resuscitation with an APP of 7.9. A total of 12 highly cited articles were published in the Emergency Medicine Journal with the highest CPP${}_{2019}$ of 184. Unfallchirurg had the lowest IF${}_{2019}$ of 0.677 (ranked 25${}^{\mathrm{th}}$ ) and published eight highly cited articles with CPP${}_{2019}$ of 133.

3.4 Countries, institutions, and authors

There were 857 highly cited articles (95% of 898 highly cited articles) with author affiliation information in SCI-EXPANDED from 46 countries. Altogether, 749 (87% of 857 articles) were single country articles from 29 countries and 108 (13%) were internationally collaborative articles from 43 countries. Six publication indicators listed below were applied to compare the top ten productive countries (Table 3) [21, 28]: total highly cited articles (TP), independent articles (IP), internationally collaborative articles (CP), first-author articles (FP), corresponding-author articles (RP), and single-author articles (SP). The top 10 most productive countries published 811 articles (95% of the 857 articles and 95% of TC${}_{2019}$ of 142,076). Seven European countries, two American countries, and one Oceania country were ranked in the top 10 publications. Japan with eight highly cited articles ranked top in Asia. The USA dominated in the six publication indicators with TP of 565 highly cited articles (66% of 857 highly cited articles), IP of 500 articles (67% of 749 independent articles), CP of 65 articles (60% of 108 internationally collaborative articles), FP of 538 articles (63% of 857 first-author articles), RP of 507 articles (62% of 813 corresponding-author articles), and SP of 28 articles (58% of 48 single-author articles).

In total, 417 highly cited articles (49% of 857 highly cited articles) instituted independent articles and 440 (51%) were inter-institutionally collaborative articles. Six publication indicators [29] were applied to compare the top 15 institutions with TP $>$ 15 (Table 4). Harvard University in the USA with 36 highly cited articles (4.2% of 857 highly cited articles) and CP of 31 articles (7.0% of 440 inter-institutionally collaborative articles) ranked top, respectively. The University of California Davis in the USA dominated in three publication indicators with IP of nine articles (2.2% of 417 institutionally independent articles), FP of 12 articles (1.4% of 857 first-author articles), and RP of 12 articles (1.5% of 813 corresponding-author articles). Also, Western Hospital in Australia, the University of Gothenburg in Sweden, and the University of Lund Hospital in Sweden published two single-author articles, respectively.

Ho proposed the Y-index indicator, which is related to the number of first-author highly cited articles (FP) and corresponding-author highly cited articles (RP). The Y-index combines two parameters (j, h) to assess both the publication potential and the characteristics of the contribution as a single index. This indicator has also been applied to compare highly cited authors in Web of Science categories of health care sciences and services [6] and dentistry, oral surgery and medicine [9]. The Y-index is defined as [5, 10]

where j (a constant related to publication quantity) is the publication potential, and h (describes the proportion of RP to FP) is publication characteristics. The greater the value of j, the more the first- and corresponding-author contributes to the highly cited articles.

h = $\pi$ / 2, indicates an author that has only published corresponding-author articles, j is the number of corresponding-author articles;

$\pi$ / 2 $>$ h $>$ 0.7854 indicates an author with more corresponding-author articles;

h = 0.7854 indicates that an author has the same number of first- and corresponding-author articles;

0.7854 $<$ h $<$ 0 indicates an author with more first-author articles;

h = 0, indicates an author that has only published first-author articles, j is the number of first-author articles.

In total, 815 (91% of 898) highly cited articles in the Web of Science category of emergency medicine with both first- and corresponding-author information was used to calculate Y-index for authors. A total of 815 highly cited articles were contributed by 3,301 authors. Particularly, 2,553 (77% of 3,301 authors) authors did not have any first- or corresponding-author articles with Y-index = (0, 0); 76 (2.3%) authors only published corresponding-author articles with h = $\pi$ / 2; 33 (1.0%) authors published more corresponding-author articles with $\pi$ / 2 $>$ h $>$ 0.7854; 518 (16%) authors published the same number of first- or corresponding-author articles with h = 0.7854; seven (0.21%) authors published more first-author articles with 0.7854 $>$ h $>$ 0; and 114 (3.5%) authors published only first-author articles with h = 0. Fig. 2 shows the distribution of the Y-index (j, h) of the top 107 highly cited authors with j $\ge$ 3. Each dot represents one value that could be one author or many authors. For example, J.M. Pines and S.M. Green with (13, 0.8622) as well as G.D. Perkins and other 42 other authors with (4, 0.7854) and M.S. Eisenberg and 17 other authors with (3, 1.107).

T.L. Litovitz had the highest j of 18, published 18 highly cited articles on the annual report of the American Association of Poison Control Centers. Only ten of them were selected for Y-index analysis because they had first- and corresponding-author information. Litovitz was both first- and corresponding-author in nine of the ten articles. Followed by P.V. Giannoudis who published 10 highly cited articles, including six first-author and 10 corresponding-author articles with (16, 1.030). M. Blaivas (10, 0.9828) and J. Soar (10, 0.7854) had the same value for j. It is clear that both of these authors are located on the same curve (j = 10) in Fig. 2, indicating that they have the same publication potential with different publication characteristics. Blaivas (h = 0.9828) has a higher ratio of corresponding-author articles to first-author articles, than Soar (h = 0.7854). Similarly, F. Sterz (3, $\pi$ / 2), M.S. Eisenberg (3, 1.107), and C.D. Deakin (3, 0.4636) are located on the same curve (j = 3). Sterz only published corresponding-author articles, Eisenberg published more corresponding-author articles, and Deakin published more first-author articles.

Fig. 2.Distribution of the top 107 highly cited authors with their Y-index values (j $\ge$ 3).

3.5 The most frequently cited articles

The most frequently cited articles with TC${}_{\mathrm{year}}$ as citation indicator indicated their impact on a research topic. Citation indicator C${}_{\mathrm{year}}$ was proposed to evaluate the most impact articles in the most recent year [5]. These two citation indicators were applied to compare the most frequently cited articles in the Web of Science category of chemical engineering [5]. Table 5 presents the top 10 articles cited more than 600 times (TC${}_{\mathrm{year}}$$>$ 600) in the Web of Science category of emergency medicine. Among them, four articles were published in the 2000s, three in the 1990s, two in the 2010s, and one in the 1980s. The first article with TC${}_{2019}$ of 600 published in 1986 was ‘A practical score for the early diagnosis of acute appendicitis’ [30]. Alvarado reported that eight predictive factors helped diagnose acute appendicitis and came up with a diagnostic score that could help interpret a picture of acute appendicitis. This older article is still highly cited because it is relevant and valuable even to 2019 with C${}_{2019}$ of 23 (rank 49${}^{\mathrm{th}}$) and TC${}_{2019}$ of 635 (rank 8${}^{\mathrm{th}}$). Oppenheim and Renn (1978) [31] reported that older papers are still actively being used for historical purposes or the context. Publications with a clear historical significance will be cited for historical reasons [32]. Those which are cited less frequently will not become classics and will not be cited as milestone events [32]. The only classic article with TC${}_{2019}$$\ge$ 1,000 [33] in emergency medicine was entitled ‘Bone substitutes: An update’ [35] with TC${}_{2019}$ of 1,062 by P.V. Giannoudis, H. Dinopoulos, and E. Tsiridis from St James’s University Hospital in the UK. Giannoudis et al. (2005) [34] presented an overview of bone grafts and graft substitutes available for clinical applications in the classic article in 2005.

The journals in which these top 10 articles published were Annals of Emergency Medicine (IF${}_{2019}$ = 5.799; ranked 1${}^{\mathrm{st}}$ ) with five articles, Resuscitation (IF${}_{2019}$ = 4.215; ranked 2${}^{nd}$) with three articles, Academic Emergency Medicine (IF${}_{2019}$ = 3.064; ranked 6${}^{\mathrm{th}}$ ) with one article, and Injury-International Journal of the Care of the Injured (IF${}_{2019}$ = 2.106; ranked 12${}^{\mathrm{th}}$) with also one article. There was a strong relation between TC${}_{2019}$ and IF${}_{2019}$ for the most frequently cited articles in emergency medicine. Seven of the top ten articles published by first-author are from the USA and three from the UK. Only two of the top ten most cited articles in TC${}_{2019}$ were ranked in the top ten in C${}_{2019}$.

3.6 Citation history of articles the top ten articles with the TC${}_{2019}$

The citation history of an article shows characteristics of the article’s impact after publication. The citation history of the top ten articles (TC${}_{2019}$$>$ 600) is shown in Fig. 3. Earlier publications like Larsen et al. (1993) [35] had a long history of impact, but less impactful in recent years. Citation history of articles by Nolan et al. (2010) [36] and Deakin et al. (2010) [37] were a type of initially much-praised articles named by Avramescu (1979) [38]. The citation history of articles by Giannoudis et al. (2005) [34] and Bijur et al. (2001) [39] was not recognized initially but has increased its citation with a constantly growing rate as a genial work [38]. Article by Nolan et al. (2010) [36] was the most cited in emergency medicine from 2013 to 2014 with C${}_{\mathrm{year}}$$>$ 100.

Fig. 3.Citation histories of the top 10 most frequently cited articles with TC${}_{2019}$$>$ 600.

3.7 Citation history of the top ten articles with the C${}_{2019}$

Only 44% of the top 100 articles with TC${}_{2019}$ were ranked on the top 100 with C${}_{2019}$. Citation indicator C${}_{\mathrm{year}}$, annual citations from Web of Science Core Collection in the most recent year was proposed [5, 40]. In the last decade, C${}_{\mathrm{year}}$ was widely applied for the most impactful articles in Web of Science categories of chemical engineering [5], environmental sciences [41], health care sciences and services [6], horticulture [7], and materials science-related categories [10]. The citation history of the top ten articles (C${}_{2019}$$>$ 80) is shown in Fig. 4. Five of the ten articles were published in 2015 and one in 2001, 2003, 2005, 2011, and 2016, respectively. Articles by Giannoudis et al. (2005) [34] and Bijur et al. (2001) [39] were not only ranked the top ten on C${}_{2019}$ but also the top ten on T2019. The article by Giannoudis et al. (2005) [34] was the most cited in 2016 and the article by Soar et al. (2015) [42] was the most impactful after 2016 in emergency medicine.

Fig. 4.Citation histories of the top 10 most impact articles in 2019 with C${}_{2019}$$>$ 80.

3.8 Words in article title, author keywords, and KeyWords Plus

Analysis of used words in article title, author keywords, and KeyWords Plus were proposed for the main research topics [43]. In SCI-EXPANDED, 479 (53% 898 articles) and 217 (24%) articles lacked author keywords and KeyWords Plus information, respectively. Table 6 shows the top 20 most used words in a highly cited article title, author keywords, and KeyWords Plus in emergency medicine. A total of 288 articles (32% of 898 highly cited articles), 79 (19% of 419 articles with author keyword information), and 77 (11% of 681 articles with KeyWords Plus information) included ‘emergency’, ‘cardiac arrest’, and ‘care’ in article title, respectively. ‘Resuscitation’ and ‘survival’ listed in the top 20 most used words in article title, author keywords, and KeyWords Plus, respectively. ‘Pain’ and ‘outcome’ ranked not only in the top 20 words in article title but also in the top 20 author keywords. ‘Cardiopulmonary resuscitation’, ‘cardiac arrest’, ‘ventricular fibrillation’, and ‘outcomes’ were the top 20 most used author keywords and KeyWords Plus, respectively.