Fatigue Severity Scale (FSS)

About the FSS

Fatigue is prevalent as symptom in a variety of disorders and can have varying degrees of negative impact on the patient’s quality of life. The Fatigue Severity Scale (FSS) designed by Krupp et al. evaluates impact of fatigue through a short self-report questionnaire consisting in statements that help the patient rate the severity of their fatigue symptoms as related to fatigue impact on their daily activities and lifestyle.

1. My motivation is lower when I am fatigued.

2. Exercise brings on my fatigue.

3. I am easily fatigued.

4. Fatigue interferes with my physical functioning.

5. Fatigue causes frequent problems for me.

6. My fatigue prevents sustained physical functioning.

7. Fatigue interferes with carrying out certain duties and responsibilities.

8. Fatigue is among my three most disabling symptoms.

9. Fatigue interferes with my work, family, or social life.

Each of the nine items about fatigue from the FSS is scored on a Likert scale on which 7 is Strongly Agree and 1 is Strongly Disagree.

The sum of the 9 items is then divided by 9 to obtain the average response value, hence the FSS ranges from 1 to 7. The higher the score, the greater the severity of fatigue and the negative effect on the person’s activities.

The FSS is a commonly used self-report scales to measure fatigue severity and is designed to differentiate fatigue from clinical depression, since there are similarities in the response to both.

FSS validation

In a validation study conducted by Valko et al. on a swiss cohort of 454 healthy subjects, 188 patients with multiple sclerosis (MS), 235 patients with recent ischemic stroke, and 429 patients with sleep-wake disorders, the following FSS scores were obtained:

■ 66 ± 1.64 (mean ± SD) in patients with MS;

■ 90 ± 1.85 in patients after ischemic stroke;

■ 34 ± 1.64 in patients with sleep-wake disorders.

Scores were not found to correlate with gender, age or education. Item analysis showed excellent internal consistency (Cronbach’s Alpha: 0.88) and reliability whilst test-retest variability results were 2.94 ± 0.90 vs. 2.90 ± 0.74; P = 0.27.

References

Original reference

Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD. The fatigue severity scale. Application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol. 1989 Oct; 46(10):1121-3.

Validation

Valko PO; Bassetti CL; Bloch KE; Held U; Baumann CR. Validation of the fatigue severity scale in a swiss cohort. SLEEP 2008; 31(11):1601–1607.

Other references

Rossi D, Galant LH, Marroni CA. Psychometric property of fatigue severity scale and correlation with depression and quality of life in cirrhotics. Arq Gastroenterol. 2017. 54; 4: 344-348.