Fatigue Severity Scale

Fatigue is essentially a subjective experience and often hard to measure even though it can be a major source of disablement (Belmont et al. 2006; Dittner et al. 2004). Individuals who sustain a TBI, regardless of the level of injury, often report fatigue as a constant or recurrent problem post injury (Belmont et al. 2006; Borgaro et al. 2005). Ziino and Ponsford (2005) found activities that required mental or physical effort often resulted in increased levels of fatigue.

The Fatigue Severity Scale (FSS) is a self-report questionnaire designed to assess disabling fatigue in all individuals (Krupp et al. 1989). The scale was designed to investigate fatigue/function measures, that is, the connection between fatigue intensity and functional disability (Dittner et al. 2004; Taylor et al. 2000). The FSS, which consists of nine questions, uses a 7-point Likert scale ranging from strongly disagrees to strongly agree (see below). The scores from each question are totalled with lower scores indicating less fatigue in everyday life. The total score for the FSS is calculated as the average of the individual item responses. Although the FSS was originally designed to assess fatigue in individuals with multiple sclerosis, it has been found to be sensitive to fatigue in those with a TBI (Ziino & Ponsford 2005).

Table: Characteristics of the Fatigue Severity Scale

Advantages. The FSS scale is a self-report scale that is easy to administer and can be completed quickly with minimal effort (Burger et al. 2010; LaChapelle & Finlayson 1998). The scale can be accessed and downloaded for free from www.saintalphonsus.org/documents/boise/sleep-Fatigue-Severity-Scale.pdf.

Limitations. Although the overall score of the FSS is beneficial in comparing between groups, the individual questions are not able to do so (LaChapelle & Finlayson 1998). Because no two fatigue scales measure the same construct, it is strongly recommended that the user understand what aspect of fatigue they want to assess and why, whether or not a unidimensional or multidimensional scale should be used, and whether the scale would be beneficial to the population of interest (Dittner et al. 2004). Another major concern with the scale is the use of a 7-point Likert scale (completely disagree to completely agree). It is believed that ≥6 categories on any rating scale obscures the distinction between the categories. The collapsing of the options to three (i.e., disagree, neutral, agree) may improve the measure (Burger et al. 2010). The FSS has not been found to be a good instrument for measuring cognitive levels of fatigue (Amtmann et al. 2012). 

 

Summary-Fatigue Severity Scale

Interpretability: The FSS has been shown to be a valid and reliable scale for several populations including the ABI population (Ziino & Ponsford 2005). Regardless, the scores on the FSS are easy to interpret and are used to assess patients for fatigue post injury. Items on the scale can be open to interpretation as the word fatigue may mean something different to each individual (Burger et al. 2010).

Acceptability: The scale has been shown to be both valid and reliable with a variety of populations. It has been shown to have good internal consistency and is sensitive to change in fatigue levels over time.

Feasibility: The FSS is a self-administered scale that does not require any training to use and is available in several languages.

 

Table: Fatigue Severity Scale Evaluation Summary

Reliability

Validity

Responsiveness

Rigor

Results

Rigor

Results

Rigor

Results

Floor/ceiling

+++

 

++ (TR)

++ (IC)

+++

++

+

+

+

NOTE: +++=Excellent; ++=Adequate; +=Poor; N/A=insufficient information; TR=Test re-test; IC=Internal Consistency; IO=Interobserver; Varied (re. floor/ceiling effects; mixed results).