Minimal Clinically Important Differences (MCID) for the Functional Assessment of Chronic Illness Therapy Fatigue Scale in Patients with Systemic Sclerosis

Abstract

(1) Background: Systemic sclerosis (SSc) is characterized by significant fatigue, causing diminished quality of life (QoL). The aim of this study was to examine fatigue levels and their associations with clinical factors and determine the minimal clinically important difference (MCID) value for the Functional Assessment of Chronic Illness Therapy Fatigue Scale (FACIT-FS). (2) Methods: A total of 160 SSc patients and 62 individuals without SSc were followed-up over a 12-month period by measuring the FACIT-FS and the Visual Analogue Scale and the Short Form 36 Vitality Score analyzing changes in exhaustion. (3) Results: Fatigue was strongly correlated with HRQoL, level of pain, emotional disorders, physical capability and functionality. The MCID values for FACIT-FS were calculated as -3 for deterioration and +4 for improvement after a 12-month follow-up. The predictors of improvement of fatigue from baseline parameters were the significant disease activity, the patients' poorer functionality and the short disease duration. Patients with scleroderma-related interstitial lung disease at baseline had approximately tripled risks for worsening fatigue. The independent influential factors regarding the changing of FACIT-FS were improving or worsening in the same direction in reference to physical condition, gastrointestinal and emotional factors. (4) Conclusions: Fatigue is a multi-dimensional symptom, which is strongly correlated to HRQoL. MCID values of FACIT-FS can be useful tools in monitoring the changes of HRQoL in clinical trials and in daily practice among patients with SSc.

Keywords: fatigue; fatigue scale; functional assessment of chronic illness therapy; health-related quality of life; minimal clinically important difference; systemic sclerosis.

Figure 1

The discriminating ability of the Functional Assessment of Chronic Illness Therapy Fatigue Scale calculated with ROC curves, and sensitivity and specificity of the minimal clinically important difference values regarding the Visual Analogue Scale for Fatigue for (a) worsened, (b) improved; and the Short Form 36 Vitality scores for (c) worsened, (d) improved, based on data of the 144 followed patients with systemic sclerosis. ROC, receiver operating characteristic curve; AUC, Area Under the Curve.

Figure 1

The discriminating ability of the Functional Assessment of Chronic Illness Therapy Fatigue Scale calculated with ROC curves, and sensitivity and specificity of the minimal clinically important difference values regarding the Visual Analogue Scale for Fatigue for (a) worsened, (b) improved; and the Short Form 36 Vitality scores for (c) worsened, (d) improved, based on data of the 144 followed patients with systemic sclerosis. ROC, receiver operating characteristic curve; AUC, Area Under the Curve.

Figure 2

Results of the Random Forest algorithm for the FACIT-FS changes to select the most important factors regarding alterations in levels of fatigue during 12-month follow-up in 144 followed patients with systemic sclerosis. (a) Potential predictors among the baseline parameters; (b) Influencing factors of the changes of the results FACIT -FS during the follow-up. Y axis represents the relative variable importance (Arbitrary unit). All variables beyond the red dashed line are considered as potential predictors. rEUSTAR AI, revised European Scleroderma Trials and Research Group Activity Index; CHFS, Cochin Hand Function Scale; Duration, Disease Duration Time; HAQ, Health Assessment Questionnaire Disability Index; mRSS, Modified Rodnan Skin Score; ILD, Interstitial Lung Disease; VAS, Visual Analogue Scale; FACIT-EWB, The Functional Assessment of Chronic Illness Therapy Emotional Well-Being; BMI, Body Mass Index; MMSE, Mini Mental State Examination; LVMI, Left Ventricular Mass Index; 6MWT, Six-minute Walk Test; lcSSc, limited cutaneous Systemic sclerosis; dcSSc, diffuse cutaneous Systemic sclerosis; UCLA GIT, University of California, Los Angeles Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument 2.0; Hgb, Hemoglobin; RP VAS, VAS for Raynaud’s Phenomena; Pinch, Pinch Strenght; LVEF, Left Ventricular Ejection Fraction; DLCO, Diffusing Capacity for Carbon Monoxide; MMT8; Manual Muscle Testing-8; DU VAS, VAS for Digital Ulcers; DAS28, Disease Activity Score 28; SF36-PCS, Short Form 36 Physical Component Summary; LVPWd, End-Diastolic Left Ventricular Posterior Wall thickness.

Figure 2

Results of the Random Forest algorithm for the FACIT-FS changes to select the most important factors regarding alterations in levels of fatigue during 12-month follow-up in 144 followed patients with systemic sclerosis. (a) Potential predictors among the baseline parameters; (b) Influencing factors of the changes of the results FACIT -FS during the follow-up. Y axis represents the relative variable importance (Arbitrary unit). All variables beyond the red dashed line are considered as potential predictors. rEUSTAR AI, revised European Scleroderma Trials and Research Group Activity Index; CHFS, Cochin Hand Function Scale; Duration, Disease Duration Time; HAQ, Health Assessment Questionnaire Disability Index; mRSS, Modified Rodnan Skin Score; ILD, Interstitial Lung Disease; VAS, Visual Analogue Scale; FACIT-EWB, The Functional Assessment of Chronic Illness Therapy Emotional Well-Being; BMI, Body Mass Index; MMSE, Mini Mental State Examination; LVMI, Left Ventricular Mass Index; 6MWT, Six-minute Walk Test; lcSSc, limited cutaneous Systemic sclerosis; dcSSc, diffuse cutaneous Systemic sclerosis; UCLA GIT, University of California, Los Angeles Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument 2.0; Hgb, Hemoglobin; RP VAS, VAS for Raynaud’s Phenomena; Pinch, Pinch Strenght; LVEF, Left Ventricular Ejection Fraction; DLCO, Diffusing Capacity for Carbon Monoxide; MMT8; Manual Muscle Testing-8; DU VAS, VAS for Digital Ulcers; DAS28, Disease Activity Score 28; SF36-PCS, Short Form 36 Physical Component Summary; LVPWd, End-Diastolic Left Ventricular Posterior Wall thickness.