Comparing the contents of patient-reported outcome measures for fatigue: EORTC CAT Core, EORTC QLQ-C30, EORTC QLQ-FA12, FACIT, PRO-CTCAE, PROMIS, Brief Fatigue Inventory, Multidimensional Fatigue Inventory, and Piper Fatigue Scale

BACKGROUND: To assess fatigue in cancer patients, several patient-reported outcome measures (PROMs) are available that differ in content. To support the selection of suitable measures for specific applications and to evaluate possibilities of quantitative linking, the present study provides a content comparison of common fatigue measures, scales, and item banks. We included the EORTC CAT Core, EORTC QLQ-FA12, EORTC QLQ-C30, FACIT-F, PROMIS Fatigue (Cancer item bank v1.0), Brief Fatigue Inventory (BFI), Multidimensional Fatigue Inventory (MFI-20), Piper Fatigue Scale (PFS-12), and PRO-CTCAE.

METHODS: All items of the included measures were linked to the International Classification of Functioning, Disability and Health (ICF). Additionally, they were categorized as assessing general, physical, emotional, or cognitive fatigue. Descriptive statistics were used to display the contents covered in each measure and to allow for a qualitative comparison.

RESULTS: The measures consist of 160 items in total and covered primarily contents of the ICF components 'Body functions', 'Activities and participation', and 'Environmental Factors'. Most ICF codings refer to 'b1300 Energy level' (9-67% of the codings per instrument; 47% of all coded content). Within the broad categorization of types of fatigue, most items were classified as general fatigue (33-100% of the codings per instrument; 49% of the overall item pool). While the EORTC CAT Core focuses exclusively on physical and general fatigue, FACIT and BFI additionally assess emotional fatigue. The EORTC QLQ-FA12, PROMIS, MFI-20, and PFS-12 cover all fatigue components, including cognitive fatigue.

DISCUSSION: The review provides an in-depth content comparison of PROMs assessing cancer-related fatigue. This can inform the selection of suitable measures in different clinical contexts. Furthermore, it will inform quantitative analyses to facilitate comparison of scores obtained with different PROMs.