[Diagnostic delay in rare diseases: systematic review.]

Background: The aims of the International Consortium for Rare Diseases Research (IRDiRC) include that the diagnosis of a known rare disease (RD) must be made within a year. The objective of this systematic review was to identify the scientific evidence about the time to diagnosis in patients affected by RDs and also to know if there is a diagnostic delay (more than one year) according to the objective set by the IRDiRC.

Methods: A systematic review was carried out according to PRISMA criteria in the PubMed, Scopus and Web of Science (WoS) databases. The quality of the articles was assessed using the STROBE statement.

Results: 17 articles were included. They were devoted to specific RDs, most of them metabolic diseases, neurological and disorders that affect immunity. The study designs were mainly cross-sectional, and two retrospective cohorts were also included. Most articles showed that it takes more than a year to get a diagnosis for these RDs.

Conclusions: Scientific literature quantifying the time to diagnosis is still scarce and no study addresses RDs as a whole. In most cases, it takes more than one year to obtain a diagnosis of a RD, so there is an obvious delay according to the objective set by the IRDiRC. Therefore, new advances in the RD field are necessary to reduce the time from the onset of symptoms to the accurate diagnosis.