Chronic Fatigue in Sarcoidosis

Primary outcomes

1. Fatigue Severity

   Time frame: 1 day of study participation

   Measured by a Fatigue questionnaire that has frequently been used in cohorts of sarcoidosis patients, the Multidimensional Fatigue Inventory (MFI).

   It consists of 20 items. For each item a score of 1 to 5 is possible, resulting in a total score of 20-100. Higher scores indicate a higher level of fatigue. In this study fatigue is diagnosed in patients with a total score of >53 based on the 75th percentile of norm values as primary developed by Kuhnt et al and used in several studies with cohorts of sarcoidosis patients.

2. Fatigue

   Time frame: 1 day of study participation

   In addition to the MFI the Fatigue Assessement Scale (FAS) is performed. It is frequently used in cohorts of sarcoidosis patients. With its 10 Items the possible total score varies from 10 to 50, higher scores indicate more fatigue.

3. Impact of fatigue on health-related quality of life

   Time frame: 1 day of study participation

   Assessed by the Fatigue Impact Scale (FIS). It includes 40 items resulting in a total score from 0 to 160. Higher values indicate more fatigue.

4. Cognitive functioning and underlying neural correlates

   Time frame: 1 day of study participation

   Assessed by an n-back task measuring working memory and (sustained) attention during functional magnetic resonance imaging.

   Reaction times and hit rates are measured.

5. Sarcoidosis disease activity

   Time frame: 1 day of study participation

   Is assessed by s-IL2-receptor (U/ml), ACE-polymorphism (mU/L) and Neopterin (nmol/L) values from a blood sample. Higher values indicate a higher sarcoidosis disease activity.

6. Lung function assessement

   Time frame: 1 day of study participation

   Whole body plethysmography is performed according to current recommendations. Parameters measured include total lung capacity (% predicted), vital capacity (% predicted), FEV1 (% predicted) and DLCO (% predicted).

7. Exercise Capacity

   Time frame: 1 day of study participation

   Assessed by a standardised six-minute walking test. Walking distance the patient achieves within six minutes is assessed.

8. Quality of life (self-assessment)

   Time frame: 1 day of study participation

   Assessed by the World Health Organization quality of Life Questionnaire, short form (WHO-QOL-BREF). The included Items assess aspects of quality of life in different domains: physical health domain, psychologic health domain, social relationships domain, environmental health domain, global domain. Domain scores are scaled in a positive direction, therefore higher scores denote higher quality of life. Scores from 0 to 100 are possible in each domain.

9. Depression (self-assessment)

   Time frame: 1 day of study participation

   Patients are asked to perform the ADS (Allgemeine Depressionsskala). A total score from 0 to 60 points is possible, while higher scores indicate more signs and symptoms of depression.

10. Depression (third-party-assessment)

    Time frame: 1 day of study participation

    Assessed by the Hamilton Depression Scale (HAMD). A total score of 0 to 62 points is possible with higher scores indicating more signs and symptoms of depression.

11. Anxiety

    Time frame: 1 day of study participation

    Assessed by the State-Trait-Anxiety-Inventory (STAI). It consists of two subscales, each including 20 items. For each subscale there is a possible score from 20 to 80 points with higher scores indicating more anxiety.

12. Executive functioning

    Time frame: 1 day of study participation.

    Assessed by the Trail-Making-Test (TMT-A and -B). Time necessary for completion of the task is measured, shorter periods of time indicate a better executive functioning in terms of attention.