Text duplication of papers in four medical related fields

In total, 2,469 representative Chinese medical journal papers submitted by researchers in 2020 and 2021 were included in our study. We received detailed information (institute, author, journal, publication date, etc.) about these papers, as well as the manuscripts. These papers were classified into four different groups according to the corresponding fields of research: basic medicine, health management, pharmacology and pharmacy, and public health and preventive medicine. Basic medicine studies involve the structure of the human body and how it operates, as well as causes of disease; immunology, pathogenic biology, pathology, and pathophysiology are its main focuses (Drews, 1999; Pandey, 2010). Health service management or health management science is a cross-disciplinary field of research including medicine, social science, and management science. It applies the theory and methods of social and management science to reveal the social, cultural, economic, and other impacts of population health. Its main focus is on public health policy, health law, hospital management, and medical ethics (Bener & Mazroei, 2010; Ozcan & Smith, 1998). Pharmacology and pharmacy deals with the interactions between drugs and animals or humans, particularly, the mechanisms of drug action as well as the therapeutic and other uses of drugs (Reidenberg, 1991; Shcherbakova & Desselle, 2020). Public health and preventive medicine deal with groups or populations rather than individuals, aiming to reduce the risk of disease transmission. It mainly focuses on epidemics, hygienic toxicology, nutrition, and food hygiene (Brenner & Siu, 2009; Foege, 1994).

The general similarity index was generated using the Academic Misconduct Literature Check System (AMLC, https://check.cnki.net/scheck/) developed by the China National Knowledge Infrastructure database. The majority of representative papers can be directly searched and checked in AMLC according to the information lists. For papers not included in the AMLC, we uploaded the papers and then carried out the check.

Plagiarism check systems are irreplaceable because of their comprehensive comparison of academic resources. However, the original general similarity index must be further corrected due to invalid duplication in the funding, addresses, references, etc., which are not excluded (Manley, 2023; Zhang et al., 2014). We therefore generated a corrected general similarity index based on the original AMLC index, according to the following steps: Step 1:

Excluding similar sources published in the same month as the checked papers or later.

We compared the AMLC general similarity index and the corrected index, which showed that the difference value (D-value) for all medical papers was 4.02 ± 10.43%. Pharmacology and pharmacy papers had the highest D-value (6.42 ± 10.46%), followed by basic medicine (5.21 ± 10.45%), and public health and preventive medicine (5.18 ± 10.41%), while those on health management had the lowest D-value (2.31 ± 10.34%). Mann-Whitney tests showed that the AMLC similarity index was significantly higher than the corrected index in all four fields (P < 0.001). Using the AMLC similarity index alone may lead to misjudgment of plagiarism; therefore the corrected general similarity index was used for further analysis.

A unified threshold for defining suspected plagiarism in medical journal papers has not yet been formed. The Committee on Publication Ethics has defined text duplication and recommended actions on how to proceed in cases of suspected plagiarism, but the threshold of defining suspected plagiarism or to what extent text reuse is tolerated is left to the editor’s discretion. Many studies on medical misconduct suggest a threshold of > 20%, for example, Swaan (2010) described that manuscripts submitted to Pharmaceutical Research with a similarity index > 20–25% were subject to further inspection. Baskaran et al. (2019) suggested that similarity scores of 21–50% should be considered moderate and high similarity for andrology papers. Furthermore, for Chinese medical journals, manuscripts submitted to the Chinese Journal of Nursing were required to have a similarity index ≤ 20%, while the Practical Journal of Cardiac Cerebral Pneumal and Vascular Disease also suggested a similarity score ≤ 20%, especially for review papers. As the AMLC similarity index was corrected in our study, and comparative analysis between the AMLC similarity index and the corrected index showed that a D-value of 4.02 ± 10.43%, 15% was used as the criterion for defining suspected plagiarism.

The data were not normally distributed; therefore, non-parametric tests, such as Kruskal-Wallis and Mann-Whitney tests, were performed using SPSS 26.0.

The average similarity index for 2,469 representative Chinese medical papers was 8.03 ± 7.58%, and pharmacology and pharmacy papers had the highest average similarity index (8.67 ± 5.92%), followed by health management (8.50 ± 8.85%), while those on basic medicine had the lowest value (7.33 ± 8.00%). Kruskal-Wallis tests showed that the average similarity index was significantly different among the four fields (P < 0.001), and Mann-Whitney tests showed that the average similarity index for pharmacology and pharmacy papers was significantly higher than that in other fields, except health management (Table 1).

Over time, the trend in similarity indices for papers in different fields peaked in 2011–2013, followed by a decrease since 2014. Armen et al. (2017) also observed a peak of global interest in plagiarism in 2013. The Chinese government has strengthened its emphasis on academic ethics since 2013, and many policies and rules on the management of academic misconduct released by the Chinese Ministry of Education and Ministry of Science and Technology have now been officially implemented. For example, the Rules of Dissertation Plagiarism released by the Chinese Ministry of Education was officially implemented in January 2013, which details rules on dissertation plagiarism and the supervisor’s responsibility; it has a significant and comprehensive impact on the management of academic misconduct not just for dissertations, but also on the frequent withdrawal of Chinese international publications. Organizations such as the National Nature Science Foundation of China have also strengthened their intensity of punishment for academic misconduct, which effectively reduced the occurrence of academic misconduct. We observed that the similarity index for papers in different fields all decreased over time, except those on pharmacology and pharmacy, which increased from 2.80% before 2011 to 8.62% in 2020–2021 (Figure 1).

Figure 1.

Most medical papers in our study were research articles (1,828, 74.04%). The average similarity index for review articles (9.77 ± 10.28%) was significantly higher than that for research articles (7.41 ± 6.26%). Mann-Whitney tests showed the average similarity index for reviews on health management and public health and preventive medicine was significantly higher than that of research articles (P ≤ 0.001 and 0.05, respectively). However, there was no significant difference in basic medicine (Table 2).

In total, 143 papers had similarity indices ≥ 15%, accounting for 5.80% of all papers. The percentage of papers suspected of plagiarism in health management was the highest (7.31%), followed by pharmacology and pharmacy (6.99%), while that of public health and preventive medicine was the lowest (3.82%). These results were similar to those in Table 1; papers on health management and pharmacology and pharmacy were more likely to contain suspected plagiarism than the other two fields (Table 3).

In total, 70 review papers and 73 research papers had similarity indices ≥ 15%. Most reviews were on health management (85.71%), and as shown in Table 2, the similarity indices of review articles were significantly higher than those of research articles, especially in the field of health management; this may be a reason for the highest percentage of papers suspected of plagiarism in this field (Figure 2).

Figure 2.

Each paper containing suspected plagiarism was split into three sections: introduction/background, data/methods, and results/discussion. According to the distribution of sections containing duplication, we classified all papers into two groups: plagiarism in a single section and plagiarism in multiple sections. Table 4 shows that medical papers with plagiarism in multiple sections accounted for a larger percentage (90.21%) than those with plagiarism in a single section (9.79%); the distributions of the two groups in all four fields aligned with this.

Papers in basic medicine were more likely to contain duplication in the introduction/ background (94.12%) and results/discussion section (94.12%), followed by the data/ methods section (76.47%). Most of these contained duplication in all three sections. Basic medicine studies the mechanisms of how the human body operates and how diseases occur. These mechanisms are complex and diverse and are generally explained by several existing mechanisms. If the descriptions in these papers of the existing mechanisms were similar to previous papers, this may have caused a high similarity index. For example, a study on basic medicine analyzed the pathology of Turner’s syndrome from the perspective of chromosome karyotype, and most of the duplication in this paper was about the pathology of the X and Y chromosomes in Turner’s syndrome, which had already been proved by existing studies.

Papers on pharmacology and pharmacy were more likely to contain duplication in the data/methods section. They mostly contained duplication of materials, devices, or procedures as the descriptions of these parts were almost the same as papers with similar topics or samples. These parts were required to describe things in as much detail as possible, which may explain why so many papers in this field contained duplication in this section. All health management papers containing suspected plagiarism contained duplication in the results/discussion (100%), 83.33% contained duplication in the introduction/background; most were review papers, which require comprehensive analysis of existing studies or policies. This may explain why so many papers in this field contained duplication in this section. In total, 94.74% of papers on public health and preventive medicine contained duplication in the results/discussion section, most of which was description of the demographic characteristics of respondents (age, education, gender, etc.). Papers in this field shared the same or similar questionnaires, especially for those on similar research topics, which may explain why so many papers in this field contained duplication in this section (Table 5).