Diagnostic odyssey for rare diseases: exploration of potential indicators

There are estimated to be between 5000 to 8000 rare diseases, defined as a life-threatening or chronically / debilitating disease that affects five people or fewer in 10,000. Examples include Cystic fibrosis, Duchenne muscular dystrophy and Marfan syndrome. The majority of rare diseases have a genetic origin. Of the more than three million people in the UK who may have a rare disease, half of new cases are identified in children. Because these diseases are so rare, there can be long delays before a final diagnosis is obtained, which can have serious consequences for the health of patients as they may receive sub-optimal care and support. Genomics offers the potential for much faster and cheaper diagnosis of genetically-based rare diseases.

The UK has developed a Strategy for Rare Diseases which seeks to address, among other issues, this delay in diagnosis. Since no system has yet been developed to measure or monitor changes in the time of diagnosis for most rare diseases, PIRU was asked to determine whether a system could be developed for monitoring the "diagnostic odyssey" of rare diseases, that is, the medical journey travelled by patients towards a correct diagnosis.

The team carried out:

• a review of 66 studies of 40 rare diseases to establish how the diagnostic odyssey had been investigated in the UK and elsewhere;

• a review of databases that monitored the time to diagnosis in other conditions that can have prolonged diagnostic odysseys (cancers and diabetes);

• a review of five categories of databases that offered opportunities to provide information about rare diseases diagnostic odysseys: generic hospital databases; primary care databases; rare diseases databases; specialist department databases; and the National Congenital Anomaly & Rare Disease Registration Service;

• interviews with 22 experts in the field of rare diseases.

The recommendations from this project were that: 

• monitoring of the odyssey should be retrospective in design and focus on a 'basket' of tracer diseases; 

• primary care data should form the foundation, initially restricted to data from primary care research databases; 

• the foundation provided by primary care data should be enhanced and validated by the addition of data from three other sources: rare diseases databases; specialist department databases; and patient/parent surveys; 

• these proposals should be subject to widespread consultation among all those with an interest in and expert knowledge of the clinical, diagnostic and management of these conditions; 

• whatever course of action is subsequently decided upon will need to be rigorously tested in pilot studies of two or three rare diseases.