UCSF

This study examines the psychometric properties of the Lee Fatigue and Energy Scales (visual analog version) using a Rasch model application. The relationship between fatigue and energy is also described for a convenience sample of 102 women with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) who completed the Lee Fatigue and Energy Scales in the morning and evening. Both scales were assessed for internal scale validity, unidimensionality, and uniform differential item functioning in relation to morning and evening ratings. Analyses confirmed that both the Fatigue and Energy Scales demonstrated evidence of internal scale validity and unidimensionality. Mean fatigue measures were also higher in the evening than in the morning and mean energy measures were higher in the morning than in the evening (both p<0.001), indicating that time of day is an important consideration. Fatigue and energy measures were moderately correlated with each other in the morning but not in the evening. The concepts of energy and fatigue were inversely related, but not polar opposites in this sample. Fatigue and energy may therefore be distinct constructs that should not be used interchangeably, either in measurement or when interpreting outcomes for research or clinical purposes.