Four-item fatigue screen: replacing the Brief Fatigue Index

To develop a shorter and less burdensome cancer-related fatigue (CRF) questionnaire, the Four-Item Fatigue Scale (FIFS) was tested for validity against the Brief Fatigue Index (BFI).

On day 1, patients with cancer completed the BFI and FIFS in a random order and the reverse on day 7. Sixty-five patients were needed for an 80% power and a Spearman correlation of .7 or greater. The FIFS was compared with the BFI in fatigue severity and changes in fatigue over time. Bonferroni corrections were made for multiple comparisons with International Classification of Diseases, Tenth Revision (ICD-10) fatigue criteria.

Seventy-nine patients were enrolled, 65 patients completed both surveys. Spearman correlation between FIFS and BFI for day 1 was 0.69 (95% confidence interval [CI] 0.50-0.87) and 0.73 (95% CI 0.56-0.90) 1 week later. Fatigue severity did not predict survival with either questionnaire. Brief Fatigue Index severity correlated with ICD-10 items 1, 3, 7, and 10B. Regression analysis showed that on day 7 BFI correlated with ICD-10 items 1, 7, and 10. When the model was adjusted for day 1, only the ICD-10 item 5 correlated well in BFI over 1 week. The ICD-10 items 7 and 10 significantly correlated with day 1 FIFS fatigue changes over 7 days after adjustment for FIFS baseline score.

Four-Item Fatigue Scale has concurrent validity for fatigue using the BFI. The FIFS and BFI correlated modestly over time. Certain ICD-10 items correlated with CRF severity depending on the questionnaire.