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From publication bias to lost in information: why we need a central public portal for clinical trial data
  1. Beate Wieseler,
  2. Natalie McGauran
  1. Institute for Quality and Efficiency in Health Care, Köln, Germany
  1. Correspondence to Dr Beate Wieseler, Drug Assessment Department, Institute for Quality and Efficiency in Health Care, Köln, Germany; beate.wieseler{at}

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The availability of clinical trial records has increased markedly. This article outlines the challenges faced in information retrieval for evidence syntheses and provides a proposal for ensuring efficient and complete access to clinical trial records, namely, the establishment of a central, worldwide public portal.

Information retrieval for a health technology assessment (HTA) report

The aim of information retrieval for evidence syntheses is to identify as many relevant studies and study results as possible; detailed requirements exist for the methods to be applied, including the sources to be searched.1 In 2019, the German HTA agency, the Institute for Quality and Efficiency in Health Care (IQWiG), conducted an HTA on biologicals in rheumatoid arthritis.2 3 One hundred and eighteen relevant studies were identified for which 682 relevant documents, which were sometimes difficult to assign to a specific study, were retrieved from various sources (table 1).

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Table 1

Summary of relevant studies and documents considered in an HTA report on biologicals in rheumatoid arthritis*

Even for a large HTA agency like IQWiG, the task of identifying and processing these numerous documents was challenging. Such an extensive effort for a single HTA is unsustainable, but returning to incomplete and selective study information is not an option.

Reporting clinical trials

This situation represents the result of a long development: the starting point was publication bias in scientific journals,4 the traditional form of reporting clinical trials. The resulting controversies accelerated data transparency initiatives propagating trial registration and the reporting of summary results.5 However, even though mandatory implementation in several countries markedly improved reporting, deficits still exist,6 7 which triggered calls to release more extensive clinical trial data such as clinical study reports (CSRs). These documents are traditionally used to inform regulatory decision making and were previously …

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