OBJECTIVES : To identify the PRO tools that have been used to assess fatigue in studies published in PubMed since 1960.

METHODS : The heoro.com database collates abstracts relevant to quality of life and patient-reported outcomes from a daily systematic search of PubMed and indexes these based on a bespoke ontology of over 5,200 PRO instruments derived from this literature. We identified all PRO tools in the heoro.com ontology that have been categorised as relevant to the measurement of fatigue, and assessed the publications that had cited each instrument according to their frequency of use and the disease area and geographical setting of the studies.

RESULTS : The ontology included 41 separate instruments relevant to fatigue. Searching the heoro.com database for studies indexed to these tools identified 348 unique publications. The most frequently cited PRO tools were the Fatigue Severity Scale (FSS, 74 abstracts), the Multidimensional Fatigue Inventory (MFI, 72 abstracts) and the Functional Assessment of Chronic Illness Therapy- Fatigue (FACIT-F, 70 abstracts). Others include the Brief Fatigue Inventory, Fatigue Impact Scale, PROMIS Fatigue module, Fatigue Assessment Scale, Bell’s, Piper and Chalder’s scales and the Maastricht Questionnaire. The 348 papers measured fatigue in 76 different disease areas, the most common being cancer (86 abstracts), multiple sclerosis (50), rheumatoid arthritis (26) and hepatitis C (16). The studies included participants from 31 countries, in particular the USA (97 abstracts), the Netherlands (43), the UK (32) and Germany (26).

CONCLUSIONS : A wide range of instruments have been used to assess fatigue across many disease areas and geographical settings. On average, a new tool is reported in every 8.5 abstracts assessing fatigue. It is unclear whether this proliferation reflects a lack of awareness of the existence of these tools, their lack of availability to other researchers, or that they are not suitable for their use in a new disease.