Results dissemination from completed clinical trials conducted at German university medical centers remained delayed and incomplete. The 2014-2017 cohort

Ethics domains in full health technology assessment reports: an attempt to begin mapping the field

INTRODUCTION

Health technology assessment (HTA) reports are written for healthcare decision makers, particularly in relation to reimbursement/pricing, and are intended to assess clinical effectiveness, safety, and cost. Four additional domains are further considered in what is called a "full HTA": ethical, legal, social, and organizational aspects. The ethical aspects have long been the subject of debate regarding how they should be processed. It would be important if the following questions could be answered: Who publishes full HTA reports and how? Which methods are used in the ethics domain? What kind of results do they produce? However, such a "mapping of the field" turns out to be difficult. Despite the existence of international HTA registers, we were not able to compile a comprehensive sample of full HTA reports. Therefore, the aim of our study was rather to explore a) substantially: Which information can be expected to be (easily) found, which can only be obtained with considerable effort, and which remain (for the time being) in the dark? And b) methodologically: Is it possible to do meaningful meta-research in this field?

METHODS AND RESULTS

In the attempt to explore the possibilities of meta-research, we were able to track down and analyze thirty-nine full HTA reports from six countries.

CONCLUSIONS

While not representative of the whole field, this analysis shows the possibilities and challenges to meta-research, but nonetheless also provides some substantial insight into the characteristics of such reports, with a particular focus on the methods used to process ethical aspects.

Improving research transparency with individualized report cards: A feasibility study in clinical trials at a large university medical center

BACKGROUND

Research transparency is crucial for ensuring the relevance, integrity, and reliability of scientific findings. However, previous work indicates room for improvement across transparency practices. The primary objective of this study was to develop an extensible tool to provide individualized feedback and guidance for improved transparency across phases of a study. Our secondary objective was to assess the feasibility of implementing this tool to improve transparency in clinical trials.

METHODS

We developed study-level "report cards" that combine tailored feedback and guidance to investigators across several transparency practices, including prospective registration, availability of summary results, and open access publication. The report cards were generated through an automated pipeline for scalability. We also developed an infosheet to summarize relevant laws, guidelines, and resources relating to transparency. To assess the feasibility of using these tools to improve transparency, we conducted a single-arm intervention study at Berlin's university medical center, the Charité - Universitätsmedizin Berlin. Investigators (n = 92) of 155 clinical trials were sent individualized report cards and the infosheet, and surveyed to assess their perceived usefulness. We also evaluated included trials for improvements in transparency following the intervention.

RESULTS

Survey responses indicated general appreciation for the report cards and infosheet, with a majority of participants finding them helpful to build awareness of the transparency of their trial and transparency requirements. However, improvement on transparency practices was minimal and largely limited to linking publications in registries. Investigators also commented on various challenges associated with implementing transparency, including a lack of clarity around best practices and institutional hurdles.

CONCLUSIONS

This study demonstrates the potential of developing and using tools, such as report cards, to provide individualized feedback at scale to investigators on the transparency of their study. While these tools were positively received by investigators, the limited improvement in transparency practices suggests that awareness alone is likely not sufficient to drive improvement. Future research and implementation efforts may adapt the tools to further practices or research areas, and explore integrated approaches that combine the report cards with incentives and institutional support to effectively strengthen transparency in research.

Results reporting for clinical trials led by medical universities and university hospitals in the nordic countries was often missing or delayed

OBJECTIVES

To systematically evaluate timely reporting of clinical trial results at medical universities and university hospitals in the Nordic countries.

STUDY DESIGN AND SETTING

In this cross-sectional study, we included trials (regardless of intervention) registered in the European Union (EU) Clinical Trials Registry and/or ClinicalTrials.gov, completed 2016-2019 and led by a university with medical faculty or university hospital in Denmark, Finland, Iceland, Norway, or Sweden. We identified summary results posted at the trial registries and conducted systematic manual searches for results publications (eg, journal articles, preprints). We present proportions with 95% confidence intervals (CI) and medians with interquartile range (IQR).

PROTOCOL

https://osf.io/wua3r.

RESULTS

Among 2112 included clinical trials, 1650 (78.1%, 95% CI 76.3%-79.8%) reported any results during our follow-up; 1097 (51.9%, 95% CI 49.8%-54.1%) reported any results within 2 years of the global completion date; and 48 (2.3%, 95% CI 1.7%-3.0%) posted summary results in the registry within 1 year. The median time from global completion date to results reporting was 690 days (IQR 1103). 856/1681 (50.9%) of ClinicalTrials.gov registrations were prospective. Denmark contributed approximately half of all trials. Reporting performance varied widely between institutions.

CONCLUSION

Missing and delayed results reporting of academically led clinical trials are a pervasive problem in the Nordic countries. We relied on trial registry information, which can be incomplete. Institutions, funders, and policymakers need to support trial teams, ensure regulation adherence, and secure trial reporting before results are permanently lost.

PLAIN LANGUAGE SUMMARY

Reporting of results from clinical trials is necessary for evidence-based clinical decision-making. We followed up reporting of clinical trials in the Nordic countries sponsored by medical universities and university hospitals. Of 2112 studies completed 2016-2019 in two major trials registries, about half reported results in any form within 24 months, and more than one in five did not report results at all. These results show that there is a need for improvement in the reporting of Nordic clinical trials.

Barriers and best practices to improving clinical trials transparency at UK public research institutions: A qualitative interview study

OBJECTIVES

Since 2017, the UK government has made concerted efforts to ensure the dissemination of clinical trials conducted at public research institutions. This study aims to understand how stakeholders within these institutions responded to these pressures and modified internal policies and processes while identifying best practices and barriers to improved transparency practice.

METHODS

Research governance and trial management staff from UK public research institutions (i.e., Universities and NHS Trusts) in England, Scotland and Wales participated in semi-structured interviews. Interviews were analysed using thematic analysis, aided by the framework method.

RESULTS

Between November 2020 and July 2021, 14 individual participants were recruited from 11 different institutions. They worked in research governance, administration, and management. Almost universally, new policies and procedures have been established to ensure investigators are aware of, and supported in, fulfilling their transparency commitments, however challenges remain. Trials of medicinal products, as the most closely regulated research, consequently received the most attention. National professional networks aid in sharing knowledge and best practice within this community.

CONCLUSIONS

Investment in the institutional governance of transparency is essential to achieving optimal transparency practices. Universities and hospitals share responsibility for ensuring research is performed and reported to regulatory standards. Facing political pressure, public research institutions in the UK have made efforts to improve their transparency practice which can provide key insights for similar efforts elsewhere.

Availability of results of clinical trials registered on EU Clinical Trials Register: cross sectional audit study

Objective

To identify the availability of results for trials registered on the European Union Clinical Trials Register (EUCTR) compared with other dissemination routes to understand its value as a results repository.

Design

Cross sectional audit study.

Setting

EUCTR protocols and results sections, data extracted 1-3 December 2020.

Population

Random sample of 500 trials registered on EUCTR with a completion date of more than two years from the beginning of searches (ie, 1 December 2018).

Main outcome measures

Proportion of trials with results across the examined dissemination routes (EUCTR, ClinicalTrials.gov, ISRCTN registry, and journal publications), and for each dissemination route individually. Prespecified secondary outcomes were number and proportion of unique results, and the timing of results, for each dissemination route.

Results

In the sample of 500 trials, availability of results on EUCTR (53.2%, 95% confidence interval 48.8% to 57.6%) was similar to the peer reviewed literature (58.6%, 54.3% to 62.9%) and exceeded the proportion of results available on other registries with matched records. Among the 383 trials with any results, 55 (14.4%, 10.9% to 17.9%) were only available on EUCTR. Also, after the launch of the EUCTR results database, median time to results was fastest on EUCTR (1142 days, 95% confidence interval 812 to 1492), comparable with journal publications (1226 days, 1074 to 1551), and exceeding ClinicalTrials.gov (3321 days, 1653 to undefined). For 117 trials (23.4%, 19.7% to 27.1%), however, results were published elsewhere but not submitted to the EUCTR registry, and no results were located in any dissemination route for 117 trials (23.4%, 19.7% to 27.1).

Conclusions

EUCTR should be considered in results searches for systematic reviews and can help researchers and the public to access the results of clinical trials, unavailable elsewhere, in a timely way. Reporting requirements, such as the EU's, can help in avoiding research waste by ensuring results are reported. The registry's true value, however, is unrealised because of inadequate compliance with EU guidelines, and problems with data quality that complicate the routine use of the registry. As the EU transitions to a new registry, continuing to emphasise the importance of EUCTR and the provision of timely and complete data is critical. For the future, EUCTR will still hold important information from the past two decades of clinical research in Europe. With increased efforts from sponsors and regulators, the registry can continue to grow as a source of results of clinical trials, many of which might be unavailable from other dissemination routes.

Dissemination of Registered COVID-19 Clinical Trials (DIRECCT): a cross-sectional study

BACKGROUND

The results of clinical trials should be completely and rapidly reported during public health emergencies such as COVID-19. This study aimed to examine when, and where, the results of COVID-19 clinical trials were disseminated throughout the first 18 months of the pandemic.

METHODS

Clinical trials for COVID-19 treatment or prevention were identified from the WHO ICTRP database. All interventional trials with a registered completion date ≤ 30 June 2021 were included. Trial results, published as preprints, journal articles, or registry results, were located using automated and manual techniques across PubMed, Google Scholar, Google, EuropePMC, CORD-19, the Cochrane COVID-19 Study Register, and clinical trial registries. Our main analysis reports the rate of dissemination overall and per route, and the time from registered completion to results using Kaplan-Meier methods, with additional subgroup and sensitivity analyses reported.

RESULTS

Overall, 1643 trials with completion dates ranging from 46 to 561 days prior to the start of results searches were included. The cumulative probability of reporting was 12.5% at 3 months from completion, 21.6% at 6 months, and 32.8% at 12 months. Trial results were most commonly disseminated in journals (n = 278 trials, 69.2%); preprints were available for 194 trials (48.3%), 86 (44.3%) of which converted to a full journal article. Trials completed earlier in the pandemic were reported more rapidly than those later in the pandemic, and those involving ivermectin were more rapidly reported than other common interventions. Results were robust to various sensitivity analyses except when considering only trials in a "completed" status on the registry, which substantially increased reporting rates. Poor trial registry data on completion status and dates limits the precision of estimates.

CONCLUSIONS

COVID-19 trials saw marginal increases in reporting rates compared to standard practice; most registered trials failed to meet even the 12-month non-pandemic standard. Preprints were common, complementing journal publication; however, registries were underutilized for rapid reporting. Maintaining registry data enables accurate representation of clinical research; failing to do so undermines these registries' use for public accountability and analysis. Addressing rapid reporting and registry data quality must be emphasized at global, national, and institutional levels.

An observational study on the adherence to study registrations in German interventional and observational studies from various fields

Background

The registration of studies, especially in the case of clinical trials, is required by the declaration of Helsinki and the policies of various scientific journals. However, numerous analyses have found considerable discrepancies between published articles and accompanying trial registrations. The aim of this study is to assess such discrepancies for a sample of studies with recruiting locations in Germany. Additionally, the association between the adherence to registrations and possible involvement of Coordinating Centers for Clinical Studies (KKS) as well as Universities of Excellence was tested.

Methods

For a sample of 376 interventional or observational study registrations, we found 115 published articles. Subsequently, we searched for discrepancies in the study design, the key inclusion criteria, the interventions, the blinding, and a primary and a secondary outcome.

Results

We found discrepancies in 26% of all studies, most frequently in the secondary outcomes, where 16.5% of the secondary outcomes per study that were registered in most detail had discrepancies. When running regression models for adherence discrepancies, the only variable that had a statistically significant association with better adherence was registration on ClinicalTrials.gov. The association of potential involvement of a KKS with adherence ratings was positive, too, but statistically insignificant.

Conclusions

In summary, the amount of discrepancies between registrations and published articles remains elevated.

Reporting of retrospective registration in clinical trial publications: a cross-sectional study of German trials

OBJECTIVE

Prospective registration has been widely implemented and accepted as a best practice in clinical research, but retrospective registration is still commonly found. We assessed to what extent retrospective registration is reported transparently in journal publications and investigated factors associated with transparent reporting.

DESIGN

We used a dataset of trials registered in ClinicalTrials.gov or Deutsches Register Klinischer Studien, with a German University Medical Center as the lead centre, completed in 2009-2017, and with a corresponding peer-reviewed results publication. We extracted all registration statements from results publications of retrospectively registered trials and assessed whether they mention or justify the retrospective registration. We analysed associations of retrospective registration and reporting thereof with registration number reporting, International Committee of Medical Journal Editors (ICMJE) membership/-following and industry sponsorship using χ² or Fisher exact test.

RESULTS

In the dataset of 1927 trials with a corresponding results publication, 956 (53.7%) were retrospectively registered. Of those, 2.2% (21) explicitly report the retrospective registration in the abstract and 3.5% (33) in the full text. In 2.1% (20) of publications, authors provide an explanation for the retrospective registration in the full text. Registration numbers were significantly underreported in abstracts of retrospectively registered trials compared with prospectively registered trials. Publications in ICMJE member journals did not have statistically significantly higher rates of both prospective registration and disclosure of retrospective registration, and publications in journals claiming to follow ICMJE recommendations showed statistically significantly lower rates compared with non-ICMJE-following journals. Industry sponsorship of trials was significantly associated with higher rates of prospective registration, but not with transparent registration reporting.

CONCLUSIONS

Contrary to ICMJE guidance, retrospective registration is disclosed and explained only in a small number of retrospectively registered studies. Disclosure of the retrospective nature of the registration would require a brief statement in the manuscript and could be easily implemented by journals.

Leveraging Open Tools to Realize the Potential of Self-Archiving: A Cohort Study in Clinical Trials

While open access (OA) is growing, many publications remain behind a paywall. This limits the impact of research and entrenches global inequalities by restricting access to knowledge to those that can afford it. Many journal policies allow researchers to make a version of their publication openly accessible through self-archiving in a repository, sometimes after an embargo period (green OA). Unpaywall and Shareyourpaper are open tools that help users find OA articles and support authors to legally self-archive their papers, respectively. This study leveraged these tools to assess the potential of green OA to increase discoverability in a cohort of clinical trial results publications from German university medical centers. Of the 1897 publications in this cohort, 46% (n = 871/1897, 95% confidence interval (CI) 44% to 48%) were neither openly accessible via a journal or a repository. Of these, 85% (n = 736/871, 95% CI 82% to 87%) had a permission to self-archive the accepted or published version in an institutional repository. Thus, most of the closed-access clinical trial results in this cohort could be made openly accessible in a repository, in line with World Health Organization (WHO) recommendations. In addition to providing further evidence of the unrealized potential of green OA, this study demonstrates the use of open tools to obtain actionable information on self-archiving at scale and empowers efforts to increase science discoverability.

Empirical studies on how ethical recommendations are translated into practice: a cross-section study on scope and study objectives

BACKGROUND

Empirical research can become relevant for bioethics in at least two ways. First, by informing the development or refinement of ethical recommendations. Second, by evaluating how ethical recommendations are translated into practice. This study aims to investigate the scope and objectives of empirical studies evaluating how ethical recommendations are translated into practice.

METHODS

A sample of the latest 400 publications from four bioethics journals was created and screened. All publications were included if they met one of the following three criteria: (1) evaluative empirical research, (2) non-evaluative empirical research and (3) borderline cases. For all publications categorized as evaluative empirical research we analyzed which objects (norms and recommendations) had been evaluated.

RESULTS

234 studies were included of which 54% (n = 126) were categorized as non-evaluative empirical studies, 36% (n = 84) as evaluative empirical studies, and 10% (n = 24) as borderline cases. The object of evaluation were aspirational norms in 5 of the 84 included evaluative empirical studies, more specific norms in 14 (16%) studies and concrete best practices in 65 (77%) studies. The specific best practices can be grouped under five broader categories: ethical procedures, ethical institutions, clinical or research practices, educational programs, and legal regulations.

CONCLUSIONS

This mapping study shows that empirical evaluative studies can be found at all stages in the translational process from theory to best practices. Our study suggests two intertwined dimensions for structuring the field of evaluative/translational empirical studies in bioethics: First, three broader categories of evaluation objects and second five categories for types of best practices.

TRIAL REGISTRATION

The methodology used was described in a study protocol that was registered publicly on the Open Science Framework ( https://osf.io/r6h4y/ ).

[Transparency in clinical research: What contribution does the new EU Regulation 536/2014 make?]

Clinical studies can be more or less transparent in four areas: (a) study registration, (b) results reporting, (c) data/code sharing, and (d) study-related documents. This discussion paper explains the extent to which the EU Regulation 536/2014 (Clinical Trials Regulation - CTR) has already positively impacted the area of results reporting in interventional drug trials and how it can improve the availability of study-related documents for independent research in the future.As this positive trend exists only for the area of results reporting and for the subset of interventional drug trials addressed by the CTR so far, a problematic two-class transparency seems to be developing that distinguishes between clinical studies addressed by the CTR and the other clinical studies. Independently of the CTR, academic institutions, funders, and ethics committees should therefore address all four abovementioned areas of transparency in all clinical studies. Monitoring the implementation of transparency in clinical studies would be an important first step in order to specify the need for action. An innovation in the context of transparency of clinical trials could also arise from the fact that the new EU Portal Clinical Trials Information System (CTIS) according to the CTR makes study-related informed consent documents, study protocols, and the investigator's brochures more transparent. This would for the first time open up the opportunity of independent research and quality assurance on issues of informed consent and harm-benefit assessment in clinical research.

Publication rates in small German trials remained low five years after trial completion

OBJECTIVE

To investigate publication rates in small trials and to explore which factors are associated with publication rates in small trials, including sample size, the type and number of primary and secondary outcomes.

STUDY DESIGN AND SETTING

We studied a subgroup of 'small' trials from a pre-existing dataset (IntoValue), containing German trials completed between 2009 and 2017. Small trials were defined as phase II-III, III and IV trials with 150 or fewer participants. We performed an updated publication search and collected additional data from online trial records.

RESULTS

Out of 499 trials, 325 (65%) trials published their results in a journal article or dissertation. Median time-to-publication was 3.41 years (95% CI: 3.04-4.10). Planned sample size was not associated with publication rates, but the difference between planned and achieved sample size was (per 10% unsuccessfully recruited participants, HR = 0.95, 95% CI: 0.91-1.00). Phase III vs. II-III trials, studied intervention (device vs. other) and clearly vs. unclearly defined primary outcomes predicted a higher likelihood of earlier publication.

CONCLUSION

About 35% of small trials in Germany remain unpublished, even after an extensive follow-up period of over 9 years. Publication rates are low and were associated with sample size, trial phase and type of intervention.

Measurement challenges and causes of incomplete results reporting of biomedical animal studies: Results from an interview study

Background

Existing evidence indicates that a significant amount of biomedical research involving animals remains unpublished. At the same time, we lack standards for measuring the extent of results reporting in animal research. Publication rates may vary significantly depending on the level of measurement such as an entire animal study, individual experiments within a study, or the number of animals used.

Methods

Drawing on semi-structured interviews with 18 experts and qualitative content analysis, we investigated challenges and opportunities for the measurement of incomplete reporting of biomedical animal research with specific reference to the German situation. We further investigate causes of incomplete reporting.

Results

The in-depth expert interviews revealed several reasons for why incomplete reporting in animal research is difficult to measure at all levels under the current circumstances. While precise quantification based on regulatory approval documentation is feasible at the level of entire studies, measuring incomplete reporting at the more individual experiment and animal levels presents formidable challenges. Expert-interviews further identified six drivers of incomplete reporting of results in animal research. Four of these are well documented in other fields of research: a lack of incentives to report non-positive results, pressures to ‘deliver’ positive results, perceptions that some data do not add value, and commercial pressures. The fifth driver, reputational concerns, appears to be far more salient in animal research than in human clinical trials. The final driver, socio-political pressures, may be unique to the field.

Discussion

Stakeholders in animal research should collaborate to develop a clear conceptualisation of complete reporting in animal research, facilitate valid measurements of the phenomenon, and develop incentives and rewards to overcome the causes for incomplete reporting.

Adoption of World Health Organization Best Practices in Clinical Trial Transparency Among European Medical Research Funder Policies

Importance

Research funders can reduce research waste and publication bias by requiring their grantees to register and report clinical trials.

Objective

To determine the extent to which 21 major European research funders' efforts to reduce research waste and publication bias in clinical trials meet World Health Organization (WHO) best practice benchmarks and to investigate areas for improvement.

Design, Setting, and Participants

This cross-sectional study was based on 2 to 3 independent assessments of each funder's publicly available documentation and validation of results with funders during 2021. Included funders were the 21 largest nonmultilateral public and philanthropic medical research funders in Europe, with a combined budget of more than US $22 billion.

Exposures

Scoring of funders using an 11-item assessment tool based on WHO best practice benchmarks, grouped into 4 broad categories: trial registries, academic publication, monitoring, and sanctions. Funder references to reporting standards were captured.

Main Outcomes and Measures

The primary outcome was funder adoption or nonadoption of 11 policy and monitoring measures to reduce research waste and publication bias as set out by WHO best practices. The secondary outcomes were whether and how funder policies referred to reporting standards. Outcomes were preregistered after a pilot phase that used the same outcome measures.

Results

Among 21 of the largest nonmultilateral public and philanthropic funders in Europe, some best practices were more widely adopted than others, with 14 funders (66.7%) mandating prospective trial registration and 6 funders (28.6%) requiring that trial results be made public on trial registries within 12 months of trial completion. Less than half of funders actively monitored whether trials were registered (9 funders [42.9%]) or whether results were made public (8 funders [38.1%]). Funders implemented a mean of 4 of 11 best practices in clinical trial transparency (36.4%) set out by WHO. The extent to which funders adopted WHO best practice items varied widely, ranging from 0 practices for the French Centre National de la Recherche Scientifique and the ministries of health of Germany and Italy to 10 practices (90.9%) for the UK National Institute of Health Research. Overall, 9 funders referred to reporting standards in their policies.

Conclusions and Relevance

This study found that many European medical research funder policy and monitoring measures fell short of WHO best practices. These findings suggest that funders worldwide may need to identify and address gaps in policies and processes.

Results publications are inadequately linked to trial registrations: An automated pipeline and evaluation of German university medical centers

BACKGROUND/AIMS

Informed clinical guidance and health policy relies on clinicians, policymakers, and guideline developers finding comprehensive clinical evidence and linking registrations and publications of the same clinical trial. To support the finding and linking of trial evidence, the World Health Organization, the International Committee of Medical Journal Editors, and the Consolidated Standards of Reporting Trials ask researchers to provide the trial registration number in their publication and a reference to the publication in the registration. This practice costs researchers minimal effort and makes evidence synthesis more thorough and efficient. Nevertheless, trial evidence appears inadequately linked, and the extent of trial links in Germany remains unquantified. This cross-sectional study aims to evaluate links between registrations and publications across clinical trials conducted by German university medical centers and registered in ClinicalTrials.gov or the German Clinical Trials Registry. Secondary aims are to develop an automated pipeline that can be applied to other cohorts of trial registrations and publications, and to provide stakeholders, from trialists to registries, with guidance to improve trial links.

METHODS

We used automated strategies to download and extract data from trial registries, PubMed, and results publications for a cohort of registered, published trials conducted across German university medical centers and completed between 2009 and 2017. We implemented regular expressions to detect and classify publication identifiers in registrations, and trial registration numbers in publication metadata, abstracts, and full-texts.

RESULTS

In breach of long-standing guidelines, 75% (1,418) of trials failed to reference trial registration numbers in both the abstract and full-text of the journal article in which the results were published. Furthermore, 50% (946) of trial registrations did not contain links to their results publications. Seventeen percent (327) of trials had no links, so that associating registration and publication required manual searching and screening. Overall, trials in ClinicalTrials.gov were better linked than those in the German Clinical Trials Registry; PubMed and registry infrastructures appear to drive this difference. Trial registration numbers were more likely to be transferred to PubMed metadata from abstracts for ClinicalTrials.gov trials than for German Clinical Trials Registry trials. Most (78%, 662/849) ClinicalTrials.gov registrations with a publication link were automatically indexed from PubMed metadata, which is not possible in the German Clinical Trials Registry.

CONCLUSIONS

German university medical centers have not comprehensively linked trial registrations and publications, despite established recommendations. This shortcoming threatens the quality of evidence synthesis and medical practice, and burdens researchers with manually searching and linking trial data. Researchers could easily improve this by copy-and-pasting references between their trial registrations and publications. Other stakeholders could build on this practice, for example, PubMed could capture additional trial registration numbers using automated strategies (like those developed in this study), and the German Clinical Trials Registry could automatically index publications from PubMed.

Registration quality and availability of publications for clinical trials in Germany and the influence of structural factors

INTRODUCTION

Analyses of clinical trial registries (CTRs) offer insights into methodological problems of published research studies, e.g., non-publication and outcome-switching. Here, we use CTRs as a tool to evaluate clinical studies conducted in Germany and test how their registration quality is associated with time and structural factors: Coordinating Centers for Clinical Trials (KKS) and Universities of Excellence.

METHODS

We searched ClinicalTrials.gov, the DRKS, and the ICTRP for clinical trials recruiting participants in Germany. As a measure for the methodological quality, we assessed the proportion of trials that were pre-registered. In addition, the registration quality and availability of publications relating to the trials were manually assessed for a sample (n = 639). Also, the influence of the structural factors was tested using regression models.

RESULTS

We identified 35,912 trials that were conducted in Germany. 59% of trials were pre-registered. Surprisingly, Universities of Excellence had lower pre-registration rates. The influence of KKS was unclear and also difficult to test. Interventional trials were more likely to be pre-registered. Registration quality improved over time and was higher in interventional trials. As of early 2021, 49% of trials that started until the end of 2015 have published scientific articles. 187 of 502 studies on ClinicalTrials.gov for which we found published articles did not reference any in the registry entry.

DISCUSSION

The structural predictors did not show consistent relationships with the various outcome variables. However, the finding that the study type and time were related to better registration quality suggests that regulatory regimes may have an impact. Limitations of this non-pre-registered study were that no modifications to registry entries were tracked and the coarse measure of KKS involvement.