Psychometric properties of fatigue severity scale in Chinese systemic lupus erythematosus patients

Abstract

Background Fatigue is the most common symptom in Systemic Lupus Erythematosus (SLE) patients. Many fatigue instruments have been used in SLE, with Fatigue Severity Scale (FSS) mostly adopted. However, fatigue instruments haven’t been tested in the Chinese SLE population. The aim of our study was to test the psychometric properties of FSS in Chinese SLE patients. Methods A cross-sectional study was conducted. 201 patients diagnosed with SLE were enrolled in the study with convenience sampling. Fatigue score, depression score and vitality subscale score of SF-36 were collected. Floor and ceiling effects were tested. Factor analysis was conducted. Reliability and validity of FSS were also tested. Results Floor (4.50%) and ceiling (4.00%) effects were minimal. One factor was extracted, explaining 61.80% of total variance. When item1 and item 2 were deleted, one factor explained 69.54% of variance, and Cronbach’s Alpha increased from 0.92 to 0.93. Intraclass correlation coefficient (ICC) was 0.94. Fatigue correlated with both depression ( r = 0.52, P < 0.01) and vitality ( r = − 0.55, P < 0.01), indicating acceptable construct validity for original FSS. When item 1 and 2 were removed, the correlation coefficient between 7-item FSS and vitality increased ( r = − 0.58, P < 0.01), while correlation coefficient between 7-item FSS and depression remained the same ( r = 0.52, P < 0.01). Known-groups validity was verified by that patients with depression showed higher fatigue score both for 9-item ( Z = -5.56, P < 0.001) and 7-item FSS ( Z = -5.70, P < 0.001). Conclusions 9-item FSS is a reliable instrument and can be used to assess fatigue problem in Chinese SLE patients, and 7-item FSS also demonstrated good psychometric properties in the same participants.

Validation of three-item Fatigue Severity Scale for patients with substance use disorder: a cohort study from Norway for the period 2016-2020

“…The explanations for this might be related to similar phrasing and wording, as well as the order of items 2 and 3, which might affect patients' perception and interpretation, and increase their confusion. Moreover, the unidimensional FSS-9 factor model was in line with models reported in other studies that have validated the FSS-9 [2,20,27]. In those studies, however, small study populations have been a persistent issue, contributing to a potential risk of overlooking underlying multidimensional models [2,27].…”

“…The reliability analyses showed high internal consistency for the FSS-9 and FSS-3, and the internal consistency only decreased from 0.94 to 0.87 when reducing the number of items from ten (FSS-9 + VAFS) to three (FSS-3). A homogenous and substantially equal internal consistency was also found in studies evaluating the FSS-9 in other chronic diseases such as stroke [3], HCV infection [1], and multiple sclerosis [15], as well as studies that have shortened the FSS from nine to seven items [13,14,27]. Unlike other populations, patients with SUDs may have a broad spectrum of mental and physical diseases that could interfere with the patients' experiences of fatigue and how they respond to the fatigue scales [28,29].…”

Validation and Shortening Questionnaires Used in Surveys and Trials on Populations with Substance use Disorders: A Method using the Fatigue Severity Scale

“…Unidimensional factor models are frequently reported when validated FSS on other populations, including the general populations [16,23,30]. However, previous studies have noted that multidimensional models in con rmatory factor analysis could be missed due to small study populations [16,30]. Our ndings on a large population on people with SUDs con rmed that one single factor for analyzing FSS-3 matched the observations adequately.…”

“…A homogenous and substantial equal internal consistency was also found in studies evaluating FSS-9 in other chronic diseases such as stroke [15], hepatitis C virus infection [13], and multiple sclerosis [29]. A shortened FSS on seven items has also been validated on patients with systemic lupus erythematosus, HIV, or stroke to have minimal change on reliability compared to the FSS-9 [19,21,30]. Unlike other populations, people with SUDs may have a broad specter of mental and physical diseases that could interfere with the people's experience of fatigue from measurement to another [31,32].…”

“…The explanations could be that the Norwegian version had substantially similar wording of items two and three (Supplementary table 2), as well as the order of items in the questionnaire that affected people's perception of them. Unidimensional factor models are frequently reported when validated FSS on other populations, including the general populations [16,23,30]. However, previous studies have noted that multidimensional models in con rmatory factor analysis could be missed due to small study populations [16,30].…”