Fatigue Assessment Scale (FAS)

Fatigue is a major problem in a wide range of (chronic) diseases and is the most frequently described symptom and is globally recognised as a disabling symptom. Fatigue is defined as “an experience of tiredness, dislike of present activity, and unwillingness to continue”, or as a “disinclination to continue performing the task at hand and a progressive withdrawal of attention” from environmental demands.

As a gradual and cumulative process, fatigue reflects vigilance decrement and decreased capacity to perform, along with subjective states that are associated with this decreased performance. It is a general psychophysiological phenomenon that diminishes the ability of the individual to perform a particular task by altering alertness and vigilance, together with the motivational and subjective states that occur during this transition. Consequently, there is reduced competence and willingness to develop or maintain goal directed behaviour aimed at adequate performance.

This scale can be useful in tracking fatigue over time in the context of psychiatric conditions, physical illness or chronic fatigue syndrome.

The total score ranges from 10 to 50, with a higher score indicating more severe fatigue.

A normative percentile for the total score is calculated based on an adult sample (Michielsen et al., 2003), indicating how the respondent scored in relation to a typical pattern of responding for adults. For example, a percentile of 90 indicates the individual has more fatigue than 90 percent of the normal population.

Scores above 22 represent significant fatigue (De Vries et al., 2004), which corresponds to a normative percentile of 65. A horizontal dotted line is indicated on the Total Percentile graph for this cutoff score.

A description of the fatigue experienced is presented for the total score where:

• less than 22 indicates “normal” (i.e. healthy) levels of fatigue
• between 22 and 34 indicates mild-to-moderate fatigue
• 35 or more indicates severe fatigue (Hendricks et al., 2018).

There are two subscales:

1. Mental fatigue (sum of items 3, 6, 7, 8, and 9) – a measure of the cognitive impacts of fatigue for the client (e.g. lack of motivation, problems beginning tasks, problems thinking).
2. Physical fatigue (sum of items 1, 2, 4, 5 and 10) – a measure of the physical impacts of fatigue for the client (e.g. physical exhaustion, lack of energy).

The FAS has an internal consistency of .90 (Michielsen, De Vries, & Van Heck, 2003). Results on the scale also correlated highly with the fatigue-related subscales of other measures like the Checklist Individual Strength (Vercoulen et al., 1999).

For 351 adults between the ages of 21 and 65 who worked 20 or more hours per week, the mean score was 19.26 (SD = 6.52) (Michielsen et al., 2003).

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