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

Gustav Nilsonne, Susanne Wieschowski, Nicholas J Devito, Maia Salholz-Hillel, Love Ahnström, Till Bruckner, Katarzyna Klas, Tarik Suljic, Samruddhi Yerunkar, Natasha Olsson, et al.

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## To cite this version:

Gustav Nilsonne, Susanne Wieschowski, Nicholas J Devito, Maia Salholz-Hillel, Love Ahnström, et al. Results reporting for clinical trials led by medical universities and university hospitals in the Nordic countries was often missing or delayed. Journal of Clinical Epidemiology, 2025, pp.111710. 10.1016/j.jclinepi.2025.111710. hal-04975620

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Submitted on 29 Sep 2025

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ORIGINAL RESEARCH

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

Gustav Nilsonne<sup>a,b,c,*</sup>, Susanne Wieschowski<sup>c</sup>, Nicholas J. DeVito<sup>d</sup>, Maia Salholz-Hillel<sup>c</sup>,

Love Ahnström<sup>a</sup>, Till Bruckner<sup>a,e,f</sup>, Katarzyna Klas<sup>g</sup>, Tarik Suljic<sup>h</sup>, Samruddhi Yerunkar<sup>c</sup>,

Natasha Olsson<sup>a,i</sup>, Carolina Cruz<sup>j</sup>, Karolina Strzebonska<sup>g</sup>, Lars Småbrekke<sup>k</sup>,

Mateusz T. Wasylewski<sup>g</sup>, Johan Bengtsson<sup>l</sup>, Martin Ringsten<sup>m</sup>, Aminul Schuster<sup>n</sup>,

Tomasz Krawczyk<sup>g</sup>, Themistoklis Paraskevas<sup>o</sup>, Eero Raittio<sup>p,q</sup>, Luca Herczeg<sup>r</sup>,

Jan-Ole Hesselberg<sup>s</sup>, Sofia Karlsson<sup>t</sup>, Ronak Borana<sup>u</sup>, Matteo Bruschettini<sup>v,m</sup>, Shai Mulinari<sup>w</sup>,

Karely Lizárraga<sup>x</sup>, Maximilian Siebert<sup>y</sup>, Nicole Hildebrand<sup>c</sup>, Shreya Ramakrishnan<sup>z,aa</sup>,

Perrine Janiaud<sup>ab,ac</sup>, Emmanuel Zavalis<sup>ad,y</sup>, Delwen Franzen<sup>c</sup>, Kim Boesen<sup>ae</sup>,

Lars G. Hemkens<sup>ac,ab</sup>, Florian Naudet<sup>af,ag</sup>, Sofie Possmark<sup>ah</sup>, Rebecca M. Willén<sup>ai,aj</sup>,

John P.A. Ioannidis<sup>y,ak</sup>, Daniel Strech<sup>c</sup>, Cathrine Axfors<sup>y,ab,al,am,an,ao</sup>

Funding: CA reports funding for this project by the Knut and Alice Wallenberg Foundation through the Wallenberg Foundation Postdoctoral Scholarship Program at Stanford (KAW 2019.0561). FN reports funding outside this project from the French National Research Agency (ANR-17-CE36-0010), the French ministry of health and the French ministry of research; being work package leader in the OSIRIS project (Open Science to Increase Reproducibility in Science) with funding from the

European Union's Horizon Europe research and innovation programme (grant agreement No. 101094725); and being work package leader for the doctoral network MSCA-DN SHARE-CTD (HORIZON-MS-CA-2022-DN-01 101120360), funded by the EU.

* Corresponding author. Department of Clinical Neuroscience, Karolinska Institutet, Tomtebodavägen 18A, 171 77 Stockholm, Sweden.

E-mail address: gustav Nilsonne@ki.se (G. Nilsonne).

<footnote><sup>a</sup>Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden</footnote>

<footnote><sup>b</sup>Department of Psychology, Stockholm University, Stockholm, Sweden</footnote>

<footnote><sup>c</sup>QUEST Center for Responsible Research, Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Berlin, Germany</footnote>

<footnote><sup>d</sup>Bennett Institute for Applied Data Science, Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, Oxfordshire, UK</footnote>

<footnote><sup>e</sup>UiT The Arctic University of Norway, Tromsø, Norway</footnote>

<footnote><sup>f</sup>TranspariMED, Stockholm, Sweden</footnote>

<footnote><sup>g</sup>Research Ethics in Medicine Study Group (REMEDY), Jagiellonian University Medical College, Krakow, Poland</footnote>

<footnote><sup>h</sup>Faculty of Medicine, University of Sarajevo, Sarajevo, Bosnia and Herzegovina</footnote>

<footnote><sup>i</sup>Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden</footnote>

<footnote><sup>j</sup>Universidad de Guadalajara, Guadalajara, Mexico</footnote>

<footnote><sup>k</sup>Faculty of Health Sciences, Department of Pharmacy, UiT The Arctic University of Norway, Tromsø, Norway</footnote>

<footnote><sup>l</sup>Department of Medical Sciences, Uppsala University, Uppsala, Sweden</footnote>

<footnote><sup>m</sup>Cochrane Sweden, Department of Research and Education, Skåne University Hospital, Lund University, Lund, Sweden</footnote>

<footnote><sup>n</sup>School of Life Sciences, University of Westminster, London, UK</footnote>

<footnote><sup>o</sup>Department of Internal Medicine, University Hospital of Patras, Patras, Greece</footnote>

<footnote><sup>p</sup>Department of Dentistry and Oral Health, Aarhus University, Aarhus, Denmark</footnote>

<footnote><sup>q</sup>Institute of Dentistry, University of Eastern Finland, Kuopio, Finland</footnote>

<footnote><sup>r</sup>Independent Researcher</footnote>

<footnote><sup>s</sup>Department of Psychology, University of Oslo, Oslo, Norway</footnote>

<footnote><sup>t</sup>Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden</footnote>

<footnote><sup>u</sup>XLRI Jamshedpur, Jamshedpur, India</footnote>

<footnote><sup>v</sup>Division of Paediatrics, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden</footnote>

<footnote><sup>w</sup>Department of Sociology, Lund University, Lund, Sweden</footnote>

<footnote><sup>x</sup>University Center of Health Sciences (Centro universitario de ciencias de la salud, CUCS), University of Guadalajara, Guadalajara, Mexico</footnote>

<footnote><sup>y</sup>Meta-research Innovation Center at Stanford (METRICS), Stanford University, Stanford, CA, USA</footnote>

<footnote><sup>z</sup>Academy of Scientific and Innovative Research, Ghaziabad, India</footnote>

<footnote><sup>aa</sup>Indian Institute of Public Health, Hyderabad, India</footnote>

<footnote><sup>ab</sup>Research Center for Clinical Neuroimmunology and Neuroscience Basel (RC2NB), University Hospital Basel and University of Basel, Basel, Switzerland</footnote>

<footnote><sup>ac</sup>Department of Clinical Research, University Hospital Basel, and University of Basel, Basel, Switzerland</footnote>

<footnote><sup>ad</sup>Department of Learning Informatics Management and Ethics, Karolinska Institutet, Stockholm, Sweden</footnote>
Accepted 29 January 2025; Published online 1 February 2025

**Abstract**

**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. © 2025 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

**Keywords:** Trial registration; Publication bias; Metascience; Clinical trials; Evidence-based medicine; Missing results

**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.

**1. Background**

Clinical trials are a cornerstone of evidence-based medicine. Completing trials is hard work and requires a joint investment of time and resources by multiple stakeholders. Patients agree to participate and contribute their sensitive information with the premise that results may inform decision-making. Incomplete or delayed reporting impedes this goal and is a preventable research waste [1]. The large extent of incomplete and delayed reporting has prompted guidelines and mandates for trial registration and public disclosure

of results at official registries (for example, the European Union Clinical Trials Register (EUCTR) and ClinicalTrials.gov in the United States), by the World Health Organization (WHO), authorities, and funders [2–6]. Still, compliance is modest, and many registered studies never have their results uploaded in registries [7–9].

Medicinal products trials in the European Union (EU) are legally mandated by the EU clinical trials regulation to be registered in the EUCTR [10]. From 2023 onward, EUCTR is replaced with the Clinical Trial Information System (CTIS); https://euclinicaltrials.eu. In parallel,

<footnote>ªeResearch Center for Clinical Neuroimmunology and Neuroscience Basel (RC2NB), University Hospital Basel and, University of Basel, Basel, Switzerland</footnote>

<footnote>ª¹University Rennes, CHU Rennes, Inserm, Centre d'investigation clinique de Rennes (CIC1414), service de pharmacologie clinique, Institut de recherche en santé, environnement et travail (Irset), UMR S 1085, EHESP, Rennes 35000, France</footnote>

<footnote>ªgInstitut Universitaire de France, Paris, France</footnote>

<footnote>ahCompliance & Data Office, Karolinska Institutet, Stockholm, Sweden</footnote>

<footnote>a¹Department of Criminology and Police Work, Linnaeus University, Växjö, Sweden</footnote>

<footnote>a)Institute for Globally Distributed Open Research and Education (IGDORE), Gothenburg, Sweden</footnote>

<footnote>akDepartment of Medicine, Stanford University, Stanford, CA, USA</footnote>

<footnote>a¹Department of Epidemiology and Population Health, Stanford University, Stanford, California, USA</footnote>

<footnote>amDepartment of Biomedical Data Science, Stanford University, Stanford, CA, USA</footnote>

<footnote>anDepartment of Statistics, Stanford University, Stanford, California, USA</footnote>

<footnote>a)Department for Women's and Children's Health, Uppsala University, Uppsala, Sweden</footnote>
**What is new?**

**Key findings**

* Many Nordic registered clinical trials were re-reported late or not at all.

* Almost 1 in 4 trials remained unreported at the end of our search period.

* About half of registered trials had reported results 2 years after completion.

* Only 2.3% of trials posted summary results in the registry 1 year after completion.

* Many trials were registered retrospectively.

**What this adds to what was known?**

* This is the first systematic follow-up of registration and reporting of Nordic clinical trials.

* Results are consistent with findings from elsewhere, including Germany, the United Kingdom, and the United States.

**What is the implication and what should change now?**

* Nordic institutions need to support their researchers to improve registration and reporting of clinical trials.

* Nordic funders and policy makers need to improve policies and follow-up to ensure timely reporting of clinical trial results.

applications should be made to the relevant national medicines agency. The approval for marketing in the United States necessitates registration also at [ClinicalTrials.gov](https://ClinicalTrials.gov). Furthermore, EU clinical trials are legally mandated to submit summary results to the registry as soon as the summary results are available and no later than 12 months after completion [10]. The contents of summary results are defined by the EU clinical trials regulation and include trial characteristics and main outcomes. Besides the legal mandate codified in the EU clinical trials regulation, the WHO and the Declaration of Helsinki both require timely reporting of clinical trials [11,12]. The WHO joint statement on public disclosure of results from clinical trials recommends that summary results be posted on the registry within 12 months of study completion and a journal article be published within 24 months [11].

As public sector institutions and sponsors for clinical investigations, universities and university hospitals have a particular responsibility to ensure that their trials are fully and timely reported. In the United States, Germany, Poland, and Canada, benchmarking investigations have shown that

institutional activity in this regard is commonly below expectations [13–19]. Previous evaluations of summary results reporting of Nordic clinical trials in the EUCTR indicated worrisome performance [20–24]. However, those evaluations relied on summary results of trials on medicinal products reported in the EUCTR and did not attempt to find results published in journals. In this project, we therefore sought to provide a more comprehensive benchmark for all the Nordic countries, enabling comparisons with earlier studies.

We aimed to systematically evaluate the reporting of results from registered clinical trials at all Nordic medical universities and university hospitals. Our project expands the thorough manual search approach developed and validated in the respective German IntoValue project [15,16,25,26] for [ClinicalTrials.gov](https://ClinicalTrials.gov). We further include the EUCTR, the main mandated registry of Nordic medicinal product trials, and we incorporate methods and insights from the EU trials tracker [8] (as further described and expanded upon by DeVito [27]) and the Dissemination of Registered COVID-19 Clinical Trials (DIRECCT) project [28,29].

**2. Methods**

This cross-sectional meta-research study followed a pre-specified protocol ([https://osf.io/wua3r](https://osf.io/wua3r), Nov 8, 2022) that can be consulted for full method details, with amendments in [Appendix Tables 1](https://osf.io/wua3r/) and is reported according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) [30].

**2.1. Eligibility criteria**

We included clinical trials that were led by any university with a medical faculty (medical university) or university hospital in the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) and completed in 2016–2019 as per their registration in the EUCTR or at [ClinicalTrials.gov](https://ClinicalTrials.gov). Other locally used registries not internationally recognized as trial registries were not considered (eg, ResearchWeb, “Cancer studies in Sweden”, or Open Science Framework) [6,31,32]. University hospitals may be a conglomerate of several smaller hospitals, for example, Copenhagen University Hospital [33,34]. Similarly for Stockholm, we included Danderyd Hospital and Stockholm South General Hospital (Södersjukhuset), as they are university-affiliated. Trials were included regardless of phase, population, intervention, comparator, or outcome. We considered a trial to be “led by” the medical university or university hospital if the institution was listed in the EUCTR as sponsor or at [ClinicalTrials.gov](https://ClinicalTrials.gov) as lead sponsor and/or responsible party [35]. We excluded trials led by an administrative region (eg, “Region Skåne”) and trials withdrawn without enrollment. For eligible trials
present in both registries, we preferred EUCTR information for being the mandatory registry but used [ClinicalTrials.gov](http://ClinicalTrials.gov) data on status or completion dates if these were more recently updated.

As results publications, we included peer-reviewed scientific publications, preprints, doctoral theses, or published congress abstracts, with >500 words, as shorter abstracts would not be likely to permit comprehensive results reporting. The publication had to be matched to an eligible clinical trial regarding design, indication or population, intervention or treatment, and comparator if applicable. Also, the publication's primary outcome measure (or first mentioned outcome) had to be listed as an outcome measure in the registration, whether as primary or not. Our goal was to identify correct matches and not to evaluate discrepancies in primary outcome reporting.

As summary results, we included summaries posted in the EUCTR or [ClinicalTrials.gov](http://ClinicalTrials.gov) directly as tabular results, or in a file (for example, Clinical Study Report synthesis, as observed in previous work) but not links to external files or publications outside the registration page (this only occurred in two cases). We also included EUCTR results sections without analysis results but with a plausible justification (eg, low enrollment), as in previous work [27].

## 2.2. Data collection

### 2.2.1. EUCTR

We retrieved the latest dataset for the EU trials tracker [8,36] of EUCTR trials on Nov 27, 2022, with data from Nov 7, 2022. Trials registered in the EUCTR can have EudraCT protocols, one for each EU or European Economic Area country where the trial is conducted and a results section. Trials without a EudraCT protocol were not present in the dataset (ie, not uploaded or not publicly available). We accessed automatically extracted data from EUCTR country protocols and results sections (Appendix Table 2) from a custom web scraper by the EU trials tracker team [36]. Automatically identified results sections were manually verified for eligibility as summary results. Global completion dates were preferred from results sections for being the most recently updated.

### 2.2.2. [ClinicalTrials.gov](http://ClinicalTrials.gov)

We downloaded the Aggregate Analysis of [ClinicalTrials.gov](http://ClinicalTrials.gov) dataset (http://aact.ctti-clinicaltrials.org/) on Nov 27, 2022, with data from Nov 9, 2022. We automatically excluded observational studies, duplicated entries, and identified the sample with a search string for medical universities and university hospitals (Appendix Table 3). We adapted code from the IntoValue project [25,37] to extract variables (Appendix Table 2), for example, whether a trial had summary results posted at the registry.

## 2.3. Manual data extraction

Our comprehensive systematic manual search for publications, by two independent reviewers per trial, followed a stepwise process (Appendix Fig 1). First, we identified results publications linked at the registration website. Second, we searched Google with the main trial ID (ie, EudraCT number or National Clinical Trial ID; then other trial IDs if present, one at a time) and screened the first page (minimum 10 hits). Third, if no publication was so far identified, we performed another Google search with two combinations of terms from the registry (eg, title, principal investigator, intervention, disease, or other). Publication dates were extracted automatically through PubMed (for articles with PubMed IDs) and otherwise manually from the publication, preferring the earliest date among multiple available dates or eligible publications. Discrepancies regarding the earliest eligible results publication for each trial were solved by one reviewer with access to the two independent extractions and comments and uncertainties discussed with another reviewer. We publicly share our dataset with all identified potentially eligible results publications (https://github.com/cathrineaxfors/nordic-trial-reporting).

To pilot and refine the extraction forms, two reviewers (S.W. and C.A.) independently analyzed a random set of 10 trials. For training, all reviewers initially analyzed the same 10 trials, with personal feedback after checking agreement against S.W. and C.A. Reviewers repeated the training on another random set of five trials if the agreement was <100% for the existence of any eligible results publication, or if they found fewer eligible publications for >20% of trials. This occurred in 6/31 reviewers (19%).

## 2.4. Statistical analysis

Descriptive statistics for primary outcomes are presented for the total sample, per country, and per accountable institution (Appendix Table 3). Trials with multiple accountable institutions were counted for each one. The following four primary outcomes were prespecified: (a) Any results reported within 2 years of completion: number and percent, with 95% confidence interval (CI) using Wilson score, of registered clinical trials that shared results either in a publication or as summary results in the trials registry within 2 years after global completion, as the upper limit of what is mandated or ethically expected (given the WHO joint statement on reporting of clinical trials in journals) [2,4]. (b) Summary results reported within 1 year of completion: number and percent, with 95% confidence interval using Wilson score, of registered clinical trials that have summary results posted within 12 months after completion (corresponding to the time frame mandated by the EU clinical trials regulation to upload summary results in the EUCTR). For trials at [ClinicalTrials.gov](http://ClinicalTrials.gov), we apply the same timeline for consistency and to illustrate adherence to best practices [2]. (c) No results reported: Number and
percent (with 95% CI using Wilson score) of registered clinical trials that remained unreported. (d) *Time to reported results:* We calculated median time (and IQR) from trial completion (last patient's last visit for all outcomes) to the reporting of summary results or results publication, whichever occurred first, taking into account differential follow-up. This is also illustrated with a Kaplan-Meier curve. For unpublished trials, we censored the timeline at the latest date that searches were performed for that trial.

We report the following three secondary outcomes: (a) Participants in trials that are unreported (planned number) and reported (actual number, or if missing, planned number) according to registry information. (b) Prospective registration: percent (with 95% CI using Wilson score) of clinical trials that are registered before the start date of the study. This outcome is also illustrated with a Kaplan-Meier curve (time to registration after trial start). It was only calculated for trials registered at ClinicalTrials.gov, since EUCTR entries are made by national regulators [27]. (c) Number and percent of medicinal products trials identified at ClinicalTrials.gov, excluding

intervention category “dietary supplements” and phase I trials, which do not have a cross-registration in the EUCTR.

We also explored subgroup analyses for the following binary primary outcomes: (a) country (Denmark, Finland, Iceland, Norway, and Sweden); (b) intervention type (medicinal products vs other interventions); (c) single-center vs multicenter trials; (d) industry-sponsored vs other trials; and (e) enrollment (smallest, medium, and largest tertile), as given in registry, whether actual or planned. We applied posthoc statistical significance testing (Pearson's chi-squared test), Bonferroni-corrected for the number of tests (n = 15, ie, *P* < .05/15).

Sensitivity analyses were performed to explore the robustness of results for the binary primary outcomes: (a) randomized controlled trials only; (b) trials registered in the EUCTR (with or without cross-registration); (c) trials registered only at ClinicalTrials.gov; (d) excluding trials with missing status or status “unknown”; (e) recalculating institutional results only counting trials for an institution if it was the sole sponsor or listed first among sponsors; (f) using primary completion date instead of global; and (g) trials

<figure><img src="image_3.png" /><figcaption>**Figure 1.** Flowchart for the search process. Note. European Union Clinical Trials Register (EUCTR) trials were identified in the European Union (EU) trials tracker dataset (which excludes EUCTR records without any linked EudraCT protocol). ClinicalTrials.gov trials were identified in the Aggregate Analysis of ClinicalTrials.gov dataset (after excluding duplicate records and observational studies). Automatic screening for cross-registrations was done in the statistical program R (and manually verified). Manual search for cross-registration IDs was done in all results publications. Additional manual searches for cross-registrations were done for all EUCTR-registered trials and for ClinicalTrials.gov-registered medicinal product trials. Cross-registered records were merged to use the most updated information. Summary results were manually verified for all EUCTR trials to exclude trials withdrawn without any enrollment.</figcaption></figure>
<table><caption>**Table 1.** Characteristics of included trials (N = 2112)</caption><thead><tr><th>Trial characteristic<sup>a</sup></th><th>All trials,<br/>N = 2112</th><th>Trials registered in the EUCTR<br/>(with or without<br/>ClinicalTrials.gov),<br/>n = 431</th><th>Trials registered only at<br/>ClinicalTrials.gov,<br/>n = 1681</th></tr></thead><tbody><tr><td>Country</td><td></td><td></td><td></td></tr><tr><td>Denmark</td><td>1019 (48.2)</td><td>255 (59.2)</td><td>764 (45.4)</td></tr><tr><td>Finland</td><td>230 (10.9)</td><td>55 (12.8)</td><td>175 (10.4)</td></tr><tr><td>Iceland</td><td>10 (0.5)</td><td>3 (0.7)</td><td>7 (0.4)</td></tr><tr><td>Norway</td><td>328 (15.5)</td><td>33 (7.7)</td><td>295 (17.5)</td></tr><tr><td>Sweden</td><td>525 (24.9)</td><td>85 (19.7)</td><td>440 (26.2)</td></tr><tr><td>Registry<sup>b</sup></td><td></td><td></td><td></td></tr><tr><td>Registered in the EUCTR</td><td>431 (20.4)</td><td>431 (100)</td><td>N/A</td></tr><tr><td>Registered at ClinicalTrials.gov</td><td>2007 (95.0)</td><td>326 (75.6)</td><td>1681 (100)</td></tr><tr><td>Intervention type<sup>c</sup></td><td></td><td></td><td></td></tr><tr><td>Medicinal product</td><td>675 (32.0)</td><td>431 (100)</td><td>244 (14.5)</td></tr><tr><td>Not medicinal product</td><td>1437 (68.0)</td><td>N/A</td><td>1437 (85.5)</td></tr><tr><td>Design (missing, n = 3)</td><td></td><td></td><td></td></tr><tr><td>Randomized controlled</td><td>1515 (71.7)</td><td>304 (70.5)</td><td>1211 (72)</td></tr><tr><td>Nonrandomized</td><td>594 (28.1)</td><td>127 (29.5)</td><td>467 (27.8)</td></tr><tr><td>Masking (missing, n = 8)</td><td></td><td></td><td></td></tr><tr><td>Open label</td><td>1157 (54.8)</td><td>245 (56.8)</td><td>912 (54.3)</td></tr><tr><td>Any masking</td><td>947 (44.8)</td><td>186 (43.2)</td><td>761 (45.3)</td></tr><tr><td>Sponsor type<sup>d</sup></td><td></td><td></td><td></td></tr><tr><td>Industry or mixed</td><td>158 (7.5)</td><td>22 (5.1)</td><td>136 (8.1)</td></tr><tr><td>Only nonindustry</td><td>1954 (92.5)</td><td>409 (94.9)</td><td>1545 (91.9)</td></tr><tr><td>Phase</td><td></td><td></td><td></td></tr><tr><td>I</td><td>65 (3.1)</td><td>12 (2.8)</td><td>53 (3.2)</td></tr><tr><td>I-II</td><td>30 (1.4)</td><td>11 (2.6)</td><td>19 (1.1)</td></tr><tr><td>II</td><td>196 (9.3)</td><td>149 (34.6)</td><td>47 (2.8)</td></tr><tr><td>II-III</td><td>21 (1.0)</td><td>8 (1.9)</td><td>13 (0.8)</td></tr><tr><td>III</td><td>61 (2.9)</td><td>39 (9)</td><td>22 (1.3)</td></tr><tr><td>IV</td><td>240 (11.4)</td><td>196 (45.5)</td><td>44 (2.6)</td></tr><tr><td>Not given</td><td>1499 (71.0)</td><td>16 (3.7)</td><td>1483 (88.2)</td></tr><tr><td>Multicentric</td><td></td><td></td><td></td></tr><tr><td>Yes</td><td>526 (24.9)</td><td>136 (31.6)</td><td>390 (23.2)</td></tr><tr><td>No (monocentric)</td><td>1586 (75.1)</td><td>295 (68.4)</td><td>1291 (76.8)</td></tr><tr><td>Enrollment (actual or anticipated;<br/>missing, n = 1)</td><td></td><td></td><td></td></tr><tr><td>1-100</td><td>1463 (69.3)</td><td>318 (73.8)</td><td>1145 (68.1)</td></tr><tr><td>100-500</td><td>515 (24.4)</td><td>100 (23.2)</td><td>415 (24.7)</td></tr><tr><td>&gt;500</td><td>133 (6.3)</td><td>13 (3)</td><td>120 (7.1)</td></tr><tr><td>Completion year<br/>(actual or anticipated)</td><td></td><td></td><td></td></tr><tr><td>2016</td><td>515 (24.4)</td><td>107 (24.8)</td><td>408 (24.3)</td></tr><tr><td>2017</td><td>532 (25.2)</td><td>134 (31.1)</td><td>398 (23.7)</td></tr><tr><td>2018</td><td>556 (26.3)</td><td>91 (21.1)</td><td>465 (27.7)</td></tr><tr><td>2019</td><td>509 (24.1)</td><td>99 (23.0)</td><td>410 (24.4)</td></tr></tbody></table>

(Continued)
<table><caption>**Table 1. Continued**</caption><thead><tr><th>Trial characteristic<sup>a</sup></th><th>All trials,<br/>N = 2112</th><th>Trials registered in the EUCTR<br/>(with or without<br/>ClinicalTrials.gov),<br/>n = 431</th><th>Trials registered only at<br/>ClinicalTrials.gov,<br/>n = 1681</th></tr></thead><tbody><tr><td>Status</td><td></td><td></td><td></td></tr><tr><td>Completed</td><td>1675 (79.3)</td><td>349 (81.0)</td><td>1326 (78.9)</td></tr><tr><td>Terminated</td><td>149 (7.1)</td><td>61 (14.2)</td><td>88 (5.2)</td></tr><tr><td>Unknown status</td><td>288 (13.6)</td><td>21 (4.9)</td><td>267 (15.9)</td></tr></tbody></table>

EUCTR: European Union Clinical Trials Register.

Percentages may exceed 100 because of rounding.

a Total count may differ between categories because of missing data (number missing shown if > 0).

b Subcategories are not mutually exclusive.

c Medicinal product trials included all EUCTR trials, and ClinicalTrials.gov trials with the labels drug, biological, genetic, or combination product; non-medicinal product trials included ClinicalTrials.gov trials with the labels behavioral, device, diagnostic test, dietary supplement, procedure, radiation, or other.

d Among lead or collaborating sponsors.

registered only at ClinicalTrials.gov that had an actual completion date (not anticipated).

### 3. Results

We included 2112 registered trials led by 54 Nordic medical universities and university hospitals (Fig 1). Twenty-two trials were co-led by two different eligible

institutions. Most trials were on nondrug interventions, for which phase allocation was generally not applicable (Table 1). Predominant characteristics were academic-only sponsorship, small size (n < 100), and single-center organization. Denmark was the major contributor of clinical trials with 48% of the total Nordic output. In the manual searches for results publications (Nov 21, 2022–March 23, 2023), for 75% of trials, both reviewers found no publication or identified the same earliest

<figure><img src="image_4.png" /><figcaption>**Figure 2.** Share of trials with any results reporting (summary results or results publications) at the end of follow-up and within 2 years of completion. Note. CIs calculated with Wilson score (using modified Wilson score if the numerator, or the denominator minus numerator, was less than 3).</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Figure 3.** Time to first reported results (summary results or results publication, total sample, *N* = 2112). Note. For 174 trials (8.2%), results were reported before the completion date. The lowest point of the Kaplan-Meier curve is not the same as the overall proportion that remained unpublished (21.9%) since the curve shows the proportion of unpublished trials among those followed up to that specific point. The curve is restricted to 84 months due to limited data beyond this follow-up (3 trials, one of which had a publication at 85 months).</figcaption></figure>

publication; for 13%, both found at least one publication, but the earliest among these was not the same; and for 11%, one reviewer found a publication and not the other. Among trials with a results publication, the earliest publication was most often a journal article (1574/1,601, 98.3%) and rarely a preprint (18/1,601, 1.1%) or another type (9/1,601, <1%; letter to the editor, *n* = 4, doctoral thesis,

<figure><img src="image_6.png" /><figcaption>**Figure 4.** Reporting of trial results per Nordic country. Note. CIs calculated with Wilson score (using modified Wilson score if the numerator, or the denominator minus the numerator, was <3).</figcaption></figure>

*n* = 3, conference abstract, *n* = 2). Half of the earliest publications were linked at a registry (790/1,601, 49.3%). The other half were found only through our systematic Google search (768/1601 48%) or cross-referenced in a linked publication (43/1,601, 2.7%).

### 3.1. Primary outcomes

Just more than half of all trials were reported within 2 years of completion (1097/2112, 51.9%, 95% CI 49.8%–54.1%), most often only as a journal article (946/1097). Few trials had summary results posted in a trial registry within 1 year of completion (48/2112, 2.3%, 95% CI 1.7%–3%). At any time, across a follow-up time of 2.9–7.1 years after completion, summary results were still uncommon (296/2,112, 14.0%, 95% CI 12.6%–15.6%) and just over three-fourths of the trials reported any results, whether as summary results or a results publication (1650/2112 trials, 78.1%, 95% CI 76.3%–79.8%). A median of 22.7 months passed between the completion and first results reporting (690 days, IQR 1103 days). The performance of individual institutions varied widely (Fig 2; Appendix Tables 4–7). Time to first results reporting is displayed in Figure 3 and per country in Appendix Figure 2. For 174 trials, results were reported before the global completion date (ie, the day before or earlier).

### 3.2. Secondary outcomes

Unreported trials (*n* = 462) had a median planned sample size of 42 (IQR 80, range 1–15,030), with a potential total of 83,489 individuals (Denmark *n* = 51,020, Finland *n* = 5,878, Iceland *n* = 1573, Norway *n* = 11,972, and Sweden *n* = 13,046). For reported trials, (*n* = 1650), the median sample size (actual or planned) was 58 (IQR 116.75, range 2–150,000), with a total of 865,781. Prospectively registered trials among those only registered at ClinicalTrials.gov were overall 50.9% (856/1681) and varied widely between institutions (Appendix Fig 3, Appendix Table 8). Another 14% (*n* = 236) were registered within 60 days and 35% (*n* = 589) more than 60 days, after their start (Appendix Fig 4). Among trials registered at ClinicalTrials.gov likely falling under the requirement for registration in the EUCTR (nonphase-I medicinal products trials), less than two-thirds were found in the EUCTR also (195/333, 58.6%, 95% CI 53.2%–63.7%).

### 3.3. Subgroup analyses

Denmark presented the highest percentage of reported trials among the Nordic countries (Fig 4) and Norway the lowest. Large trials (vs small trials) were more likely to be reported at all, and within 2 years of completion; and medicinal product trials (vs nonmedicinal product trials) were more likely to have summary results. We found no differences per multicenter status or industry-sponsored status (Appendix Table 9).
### 3.4. Sensitivity analyses

Reporting was better for EUCTR-registered trials and worse for only ClinicalTrials.gov-registered trials than the overall sample (Appendix Table 10). Reporting of any results, and within 2 years of completion, was higher among completed trials than those terminated or with unknown status (Appendix Table 10). Other sensitivity analyses were consistent with the main results (Appendix Tables 10–13).

## 4. Discussion

### 4.1. Summary of findings

Only 52% of clinical trials led by Nordic medical universities or university hospitals were reported in adherence to WHO recommendations [11]. Timely summary results reporting in the registries was rare, with only 2% of registrations showing results 12 months after completion. Among EUCTR registrations, for which this practice is now mandatory, the proportion was 8%. For 22% of trials (planned to involve 83,489 participants), no results could be located regardless of time limit. Contrary to established recommendations, almost half of registrations were made retrospectively, limiting their usefulness [38,39]. Among trials registered at ClinicalTrials.gov, those likely falling under the requirement for registration in the EUCTR, short of two-thirds, were also found in the EUCTR. These results show that registration and reporting of clinical trials in the Nordic countries can be considerably improved.

### 4.2. Comparison to earlier research

Overall, results from the present project are similar to earlier findings in other settings. The IntoValue project followed up reporting of trials from German university medical centers, registered in ClinicalTrials.gov or in the German Clinical Trials Register (DRKS) [14–17]. Our present results are similar to theirs, where out of 1658 trials completed in 2014–2017, 43% published results either as summary results or in journal articles within 24 months after completion, and 5 years after completion, 70% of the trials were published [15]. In Canada, a follow-up of 6720 trials on ClinicalTrials.gov from 2009 to 2019 showed that 59% were registered prospectively, and 39% reported summary results in the registry [19]. This proportion is considerably higher than in the present study, mainly because they included many industry-sponsored studies, among which summary results reporting was more common. Of trials registered 2009–2014, 55% were subsequently published in an academic journal [19]. In Poland, among 305 interventional clinical trials at academic medical centers registered on ClinicalTrials.gov and completed 2009–2013, 80% had been published as articles or posted summary results in 2019 [18]. Results were posted within a year of study completion and/or published within 2 years

of study completion for 43% of trials. In the United States, a sample of 400 trials from ClinicalTrials.gov was followed up for 36 months, and results were found for 61% of trials either in the registry or on PubMed [40].

### 4.3. Strengths and limitations

A strength of this project is that extensive online manual searches were carried out to track results publications, inspired by and further developing previous methods [14–17]. Investigators were trained with sample searches, and two independent investigators performed searches for each trial, relying not only on trial identifiers but also on other characteristics. Although some results publications may still have been missed, we believe that a high coverage has been reached. A further strength is the careful manual work to identify and validate cross-registrations.

The following limitations should be noted. This project relied on information in trial registries, which can be incomplete and not updated since the initial entry. For instance, completion date and enrollment numbers can reflect what was estimated at the start, rather than actual numbers. A recent study of registered Covid-19 trials found that registrations with actively updated completion status showed a higher proportion of results reported compared to others [41]. We did not contact primary investigators nor sponsors to verify trial status; however, a survey in a sample of German registered trials showed only minor changes after status verification by the primary investigator [42]. The planned number of participants in unreported trials is likely an overestimation compared to final enrollment [43,44], but the lack of results for their trials still reflects extensive research waste. The registries contain a heterogeneous sample of trials, some of which are intended to inform clinical practice and some of which are closer to basic research.

In the EUCTR, registration dates and start dates have particular limitations [27]. While all trials on the EUCTR should be prospectively registered as they would need approvals tied to their registration before starting, it is impossible to tell from the registration when a trial actually started. Also, primary completion dates (with respect to primary outcome) are not generally registered, and we instead had to use global completion dates (last patient's last recorded data point). For trials with long follow-up of secondary outcomes, this may be much later and contributes to explaining the proportion of trials reported before their completion date. Using a stricter cutoff, numbers for timely reporting may be even lower. We expect many trials to erroneously appear as ongoing although they are actually completed or terminated [45]; for Norway, this affects a particularly large proportion of trials [24]. Timely reporting may have been overestimated, if trials without status update are less likely to have reported results. In contrast to the EUCTR, ClinicalTrials.gov lists anticipated completion dates, which allowed us to include trials without an active status update. However, since some of these trials may be still ongoing, this may partly explain the difference in the
results between the two registries. In our sensitivity anal-
ysis among ClinicalTrials.gov-registered trials with
“actual” completion dates, results were in-between.

Cross-registration of trials in our examined registries varied in extent and content overlap. If some were without overlapping or similar titles, we may have missed them and hence double-counted some trials. These might appear un-reported if summary results were posted in one registration and not the other. Information in cross-registrations was often inconsistent in terms of key study dates and status. We chose to merge cross-registrations to use the most up-dated information.

Not all trials are registered, and those not registered may
be more likely to also not be reported [27,46]. Trials that
were not prospectively registered may have had a higher
likelihood of becoming registered if the investigators were
in the process of reporting. Also, we did not scrutinize the
quality of the reporting nor the alignment with registered
outcomes. These reasons may contribute to overestimating
the proportion of meaningfully reported trials.

4.4. *Implications and future perspectives*

Nordic academic sponsors need to improve clinical trials registration and reporting. Joint work is needed by multiple stakeholders to enable continuous monitoring of clinical trials reporting and to align resource allocation with best practices. The Nordic Trial Alliance Working Group on Transparency and Registration has recommended institutions to implement standard operating procedures to support their researchers and ensure complete registration and reporting [47]. Resources summarizing how universities can improve clinical trial reporting are also compiled online (eg, https://www.transparimed.org/resources). Possible solutions are already implemented by some sponsoring institutions, for example, as recently reported by one Nordic institution (Karolinska Institutet) with dedicated support staff for trial registration and active follow-up of reporting [48]. In Germany, efforts are ongoing to involve trial funders in creating and implementing strategies for increased reporting [49], and other examples on lobbying activities or infrastructural support structures exist in the United States and United Kingdom [50–52].

There may be several reasons for slow or missing report-
ing of clinical trials [27]. Trials may be underfunded, and
institutional support may be lacking, leaving the individual
researcher with the sole responsibility for trial reporting.
Summary results posting can be difficult for researchers un-
familiar with registry interfaces and procedures. Reporting
of results in journals typically requires manuscripts to pass
editorial and/or peer review, a process largely outside of the
researcher's control. More fundamentally, current models
for assessing academic merits may not be well-aligned with
transparent reporting [53]. Researchers may perceive jour-
nal publications and journal impact factors as the main
criteria for funding and promotion. This misalignment

may be to the detriment of reporting summary results in
registries or reporting negative results or those contrary to
established opinion and therefore more difficult to publish
in journals. These obstacles highlight the role of preprints
as a vehicle for rapid and unhindered dissemination of
research results. Assessments of the merit of articles report-
ing clinical trials could be improved by taking into account
whether studies were prospectively registered and results
were reported in a timely and complete manner [54].

5. Conclusion

We found considerable room for improvement of registra-
tion and reporting of Nordic clinical trials. Late and incom-
plete reporting reduces the accuracy and validity of the
evidence base used for clinical decision-making and hampers
the advancement of knowledge. Future extensions should be
made for industry-sponsored trials [55] and trials in other reg-
istries. Joint action by stakeholders is needed, especially at
the initiative of academic institutions, to support, monitor,
and incentivise trials registration and timely reporting.

CRediT authorship contribution statement

**Gustav Nilsonne:** Writing – original draft, Methodol-
ogy, Conceptualization. **Susanne Wieschowski:** Writing
– review & editing, Methodology, Investigation, Conceptu-
alization. **Nicholas J. DeVito:** Writing – review & editing,
Software, Methodology, Conceptualization. **Maia Salholz-**
**Hillel:** Writing – review & editing, Software,
Methodology, Conceptualization. **Love Ahnström:**
Writing – review & editing, Investigation. **Till Bruckner:**
Writing – review & editing, Methodology, Investigation,
Conceptualization. **Katarzyna Klas:** Writing – review &
editing, Investigation, Conceptualization. **Tarik Suljic:**
Writing – review & editing, Investigation. **Samruddhi**
**Yerunkar:** Writing – review & editing, Investigation,
Conceptualization. **Natasha Olsson:** Writing – review &
editing, Investigation. **Carolina Cruz:** Writing – review
& editing, Investigation. **Karolina Strzebonska:** Writing
– review & editing, Investigation, Conceptualization. **Lars**
**Småbrekke:** Writing – review & editing, Investigation,
Conceptualization. **Mateusz T. Wasylewski:** Writing – re-
view & editing, Investigation. **Johan Bengtsson:** Writing –
review & editing, Investigation. **Martin Ringsten:** Writing
– review & editing, Investigation, Conceptualization. **Ami-**
**nul Schuster:** Writing – review & editing, Investigation,
Conceptualization. **Tomasz Krawczyk:** Writing – review
& editing, Investigation. **Themistoklis Paraskevas:**
Writing – review & editing, Investigation, Conceptualiza-
tion. **Eero Raittio:** Writing – review & editing, Investiga-
tion, Conceptualization. **Luca Herczeg:** Writing – review
& editing, Investigation. **Jan-Ole Hesselberg:** Writing –
review & editing, Investigation, Conceptualization. **Sofia**
**Karlsson:** Writing – review & editing, Investigation.
**Ronak Borana:** Writing — review & editing, Investigation.
**Matteo Bruschettini:** Writing — review & editing, Investigation, Conceptualization.
**Shai Mulinari:** Writing — review & editing, Investigation, Conceptualization.
**Karely Lizárraga:** Writing — review & editing, Investigation.
**Maximilian Siebert:** Writing — review & editing, Investigation.
**Nicole Hildebrand:** Writing — review & editing, Investigation, Conceptualization.
**Shreya Ramakrishnan:** Writing — review & editing, Investigation.
**Perrine Janiaud:** Writing — review & editing, Investigation, Conceptualization.
**Emmanuel Zavalis:** Writing — review & editing, Investigation.
**Delwen Franzen:** Writing — review & editing, Investigation.
**Kim Boesen:** Writing — review & editing, Conceptualization.
**Lars G. Hemkens:** Writing — review & editing, Conceptualization.
**Florian Naudet:** Writing — review & editing, Conceptualization.
**Sofie Possmark:** Writing — review & editing, Conceptualization.
**Rebecca M. Willén:** Writing — review & editing, Conceptualization.
**John P.A. Ioannidis:** Writing — review & editing, Methodology, Conceptualization.
**Daniel Strech:** Writing — review & editing, Methodology, Conceptualization.
**Cathrine Axfors:** Writing — original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.

Declaration of competing interest

There are no competing interests for any author.

Acknowledgments

The title page and author contributions section of this
document was made using the free open-source tool tenz-
ing, https://rollercoaster.shinyapps.io/tenzing/.

Supplementary data

Supplementary data to this article can be found online at
[https://doi.org/10.1016/j.jclinepi.2025.111710](https://doi.org/10.1016/j.jclinepi.2025.111710).

Data availability

All code is available at: https://github.com/cathrineax
fors/nordic-trial-reporting On Github there are other links
to the raw data.

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