International Clinical Trials Registry Platform (ICTRP)

Clinical Trials in Children

How the search works

The ICTRP Search Portal identifies clinical trials in children by applying a set of filters specifically developed for this purpose. In reviewing the database, a significant portion registered trials now include age information. In order to better identify trials in children, the algorithm for searching has been revised.

In this algorithm, records will first be screened with an "age" filter. This filter will identify trials with searchable age information and flag records where participants include individuals between birth to 18 completed years. Following this, a second filter consisting of key terms will be applied to records without searchable age information and to all records from other registries. The CTC site will combine the results of these two filters.

The filter of key terms was created by firstly consulting child health experts who identified terms relevant to children and adolescents (including conditions and interventions). The Unified Medical Language System (UMLS) Metathesaurus was then used to identify synonyms and other relevant terms. This filter, of over 4000 key terms, has been used to identify children's trials since the launch of this website. Modifications have and will continue to be made in order to better identify children's trials.

Why is a two-step filter necessary?

The best way to identify clinical trials in children would be to search by age. Unfortunately, not all records on the ICTRP Search Portal contain age information in an easily searchable format. By using a two step algorithm, we are able to identify records of trials with searchable age information and then screen the set of records which do not by keywords. This increases our ability to correctly identify children's trials.

We hope that standards for data collection will be implemented in the near future (such as those being developed by CDISC), and that WHO Primary Registries will apply these standards and collect age information in a more searchable format.

How accurate is the filter?

Searching the complete text of registered records remains problematic. We expect that at least 80% of trials in children will be identified by the age filter, alone. The remainder must be identified by keywords. However, when trials are identified by keywords, the search may include trials that it should not or miss others. By making modifications to the filter based upon feedback of users, we hope to continue to improve its accuracy.

Please give us your feedback

If you have suggestions for improving the filter, or would like to see details of the search algorithm or the complete list of terms it includes, please contact us.

Search for trials

Search Filter for Clinical Trials in Children

Details are kept in the version history document


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This is the first phase of the ICTRP Clinical Trials in Children website. Expect content to grow and the search filter to be refined over time. Your feedback appreciated.

Contact Details


World Health Organization
Avenue Appia 20
1211 Geneva 27