Turkish Version of the Chalder Fatigue Scale: An Investigation of Its Psychometric Properties in Healthy Young Adults
Conditions: Fatigue, Healthy
Sponsor: Hacettepe University

Official Title of the Study:  
Turkish version of the Chalder Fatigue Scale: An investigation of its psychometric 
properties in healthy young adults 
 
 
NCT number: 03969667 
 
Document Date: May 21, 2020 
 
Document Type: Study Protocol and Statistical Analysis Plan 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Study Protocol and Statistical Analysis Plan 
This research was carried out in 2 stages. The first stage of the research was to develop the 
Turkish version of the Chalder Fatigue Scale (CFS), and the second stage was to examine the 
psychometric properties of the scale. 
Stage 1: Adaptation of the CFS into Turkish 
Adaptation of the CFS into Turkish was completed in 6 steps and the procedures was 
described below. 
Step 1-Translation: Two bilingual Turkish translators participated; one of them was a 
physiotherapist who knows the instrument, and the other one was English linguist who had 
no professional relation with the medical field, nor information about the CFS. They carried 
out the translation of the CFS from English into Turkish independently, generating the 
translated versions (T1 and T2). 
Step 2-Synthesis: The two translators and the researchers discussed the T1 and T2. After the 
two translated versions were compared, they synthesized the versions into one translated 
version (T12) by reaching an agreement. 
Step 3-Back translation: Two native English speaker with fluent Turkish language, who were 
not familiar to the original instrument, carried out the back translation of the T12 from 
Turkish into English so the re-translated versions (TR1 and TR2) were formed.  
Step 4-Expert committee review: A committee of the researchers and the translators 
compared the original CFS with five translated versions (T1, T2, T12, TR1, TR2), obtained 
in the first 3 steps, to check whether all instruments were similar. The consensus index 
among the judges was calculated as ≥ 80% for each of the items in scale. The committee 
verified the items adequate in accordance with following equivalencies: semantic, idiomatic, 
experimental, and conceptual. Then, the translators and researchers agreed on the prefinal 
Turkish version of the CFS (pCFS-T) 
Step 5-Pretesting: The pCFS-T was tested on 56 volunteer healthy young adults. While 
answering the scale, the participants asked to evaluate the comprehensibility of the items 
according to three-point likert scale (clearly/partially/not understandable). The aim of this 
strategy was to establish whether the pCFS-T was intelligible for this population. After the 
pretesting, it was determined that the all participants rated each of the items in the scale as 
‘clearly understandable’. 
Step 6- Final Version: All the reports and forms submitted the original developer and then 
she approved that a reasonable translation had been achieved certainly. Thus, the final 
version of the CFS (CFS-T) was eventually generated as in pCFS-T. 

Stage 2: Investigating Psychometric Properties of the Chalder Fatigue Scale-Turkish 
Investigation of reliability 
Test-retest reliability and internal consistency of the scale were examined. In order to 
determine the test-retest reliability, CFS was administered to individuals, at least 3 days and at 
most 7 days after the test. In the retest session, only CFS was applied to individuals. Cronbach 
Alpha for internal consistency and Intraclass Correlation Coefficient for test-retest reliability 
was used in the statistical analysis. 
Investigation of validity 
In our study, criterion and construct validity of CFS were investigated. The criterion validity 
of the scale was investigated with concurrent validity and predictive validity. To test the 
concurrent validity of the Chalder Fatigue Scale, its relationship with the Checklist Individual 
Strength (CIS) fatigue scale was examined. To test the predictive validity of the CFS, the 
ability of the scale to detect fatigued individuals who determined with CIS cut off score was 
examined with Receiver Operating Characteristics curve. The construct validity of the scale 
was investigated with Explanatory Factor Analysis, Confirmatory Factor Analysis and 
hypothesis testing. The hypothesis tests were applied to determine the relationship between 
CFS and Visual Analogue Scale, Beck Depression Scale, Pittsburg Sleep Quality Index, 
Nottingham Health Profile. In order to investigate the known group validity of the scale, a 
hypothesis test was applied to discriminate the scores of men and women with Mann-Whitney 
U test. To analyze all relationships, Spearman Correlation Coefficient was used.