Criteria to define rare diseases and orphan drugs: a systematic review protocol

Ghada Mohammed Abozaid, Katie Kerr, Amy McKnight, Hussain A. Al-Omar*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

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Introduction: Rare diseases (RDs) are often chronic and progressive life-threatening medical conditions that affect a low percentage of the population compared with other diseases. These conditions can be treated with medications known as orphan drugs (ODs). Unfortunately, there is no universal definition of RDs or ODs. This systematic review (SR) will identify the quantitative and qualitative criteria and the underlying rationale used internationally to define RDs and ODs. Methods and analysis: This protocol follows the conventions for the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (2015 guidelines). A SR will be conducted, including a search of the following databases: PubMed, MEDLINE, EMBASE, Scopus, Web of Science, GreyLit and OpenGrey. Eligible publications will be selected based on predetermined inclusion criteria. Extracted data will be analysed using thematic and content analyses of qualitative descriptors, whereas quantitative data will be analysed descriptively and reported in the form of frequencies and percentages. Ethics and dissemination: No ethical approval is required since this SR focuses on the secondary analysis of data retrieved from the scientific literature. The outcomes of this SR will be published as part of a PhD thesis, presented at conferences, and published in peer-reviewed journals. 

Original languageEnglish
Article numbere062126
Number of pages5
JournalBMJ Open
Issue number7
Publication statusPublished - 29 Jul 2022

Bibliographical note

Funding Information:
This systematic review is supported by the Medical Research Council's Northern Ireland Executive in support of the Northern Ireland Genomic Medicine Centre through the Belfast Health and Social Care Trust (award number: MC_PC_16018) and the Science Foundation Ireland and Department for the Economy, Northern Ireland partnership (award number: 15/IA/3152). Princess Nourah University, Riyadh, Saudi Arabia, is supporting this study through a PhD scholarship with no grant number. These funders played no role in the development of this protocol.

Publisher Copyright:


  • epidemiology
  • health economics
  • health policy

ASJC Scopus subject areas

  • Medicine(all)


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