VALIDATION DATA

In terms of normative data, the mean (SD) score in healthy adults (n = 1615) was 14.2 (4.6), compared with 24.4 (5.8) in patients with chronic fatigue syndrome (CFS) and 18.2 (6.1) in patients with FMS (n = 361 and n = 30, respectively). Many studies use the 14-item CFQ draft (score range 0-42), giving an average global fatigue score in 120 patients with systemic lupus erythematosus (SLE) of 22 (interquartile range [IQR] 16-28). Using the 14-item CFQ draft with an aggregated fifth response option (score range 0-56), the overall median fatigue in 51 patients with primary Sjögren’s syndrome (SS) was 37 (IQR) vs. 28 (IQR) in 51 control subjects (P < 0.01).

Cronbach's α was calculated in 274 general practice (GP) patients for the 14 draft items, 0.88 to 0.90 for pulling out different items one at a time (excellent values), and 0.84 and 0.82 for two domain scores (physical and mental, respectively; also excellent values). For the final version of 11 items, Cronbach's α was 0.89 in GP patients (n = 274), 0.92 in patients with CFS (n = 361), and 0.88 in a survey of GP assistants (n = 1.615). In one study that included rheumatological patients Cronbach's α was 0.93 and 0.92 for the group of patients with CFS (n = 141) and the group of patients with autoimmune diseases (n =162), respectively.

The reliability value of the test-retest, measured using the correlation coefficient of the Spearman range, was 0.55 (P < 0.001), a fair value 

The items were generated by experts, and the final 11-item CFQ covers a range of physical and mental fatigue problems and produces a domain score for each

A CFQ score of 29 of 33 discriminates patients with CFS from the general population in 96% of cases. In SLE, with the draft 14-item CFQ, mean fatigue was significantly different between patients (23.5, SEM 0.9; n = 93) and control subjects (15.0, SEM 0.6; n = 41). However, no differences were found in total CFQ or physical and mental domains between control subjects and patients with SLE or primary SS, and patients with RA alone differed from control subjects in physical fatigue (P < 0.05). In SLE, preliminary CFQ scores of 14 items were moderately associated with two measures of disease activity, the Systemic Lupus Activity Measure and the European Consensus Lupus Activity Measure (r = 0.36-0.4), and aerobic capacity (r = −0.33). In chronic upper extremity pain (n = 73), the CFQ was moderately associated with pain disability (r = 0.44) and pain intensity (r = 0.32)