VALIDATION DATA

MEASUREMENT PROPERTIES
Limitations	>=5 European languages (English)
Observations

1. RELIABILITY

A. Internal Consistency

Tested

Cronbach's (Describe)

Internal consistency showed an alpha coefficient of 0.82 for the total items of the FIQ; alpha =0.79 for the 8 items, without the 2 items concerning work, and alpha = 0.86 for the 9 sub-items of the physical function.

B. Reliability intraobserver or test-retest

Tested

Continuous scores: intraclass
correlation coefficient (ICC)
Dichotomus: Cohen kappa (Describe)

According to the original Burckhardt paper (1991) test-retest reliability correlations (Pearson´s r) for each item of the FIQ ranged from an average of 0.56 for pain to 0.95 for physical function over the six 1-week intervals.

In a paper by Rivera et ál (2004) we found the following table that depicts the test-retest reliability. Showing Spearman correlation coefficients between FIQ items performed with a difference of 1 week. All coefficients reached statistical significance for a p<0.01.

	Correlation Coefficient
Physical function	0.79
Days feel good	0.68
VAS pain	0.75
VAS fatigue	0.66
VAS morning tiredness	0.61
VAS stiffness	0.60
VAS anxiety	0.58
VAS depression	0.67
Total FIQ	0.85
Work missed days	0.83
Job Ability	0.76

C. Reliability interobserver or Measurement error

Not Tested

Standard error of measurement (SEM),
smallest detectable change (SDC) or
Limits of agreement (LoA) (Describe)

2. VALIDITY

A. Content validity: face validity

Not Tested

Expert opinion (relevance and
comprehensiveness) (Describe)

B. Construct Validity:
Structural validity

Tested

Hypotheses-testing

Not Tested

Cross-cultural validity

Tested

Brief Description

Bennett (2005) shows a summary of 7 translations of the FIQ in terms of their operating characteristics.

Each of these translations, with the exception of one, tested the construct validity with the HAQ or AIMS. All translations provided data on test-retest reliability. All but two assessed internal consistency with a Cronbach's alpha statistic. Overall, the translations performed with a validity, consistency and test-retest reliability similar to the original English original version.

First autor	Country	Internal Consistency	Test Retest	Concurrent validity assessment tested against
Offenbaecher	German	0.92	0.62-1.0	HAQ, SF-36
Bae	Korean	ND	0.53-0.96	HAQ
Kim	Korean	0.8	0.46-0.78	HAQ, SCLR-90
Perrot	French	ND	0.04-0.84	SF-36, AIMS, GHQ
Rivera	Spanish	0.82	0.61-0.85	HAQ, SF-36, SCLR-90
Samer	Turkish	0.72	0.81	HAQ
Satzi-Puttinimer	Italian	0.9	0.74-0.95	HAQ, SF-36
Buskila	Hebrew	0.93	0.8-0.96	tender point count, dolorimetry
Hedin	Swedish	0.83	0.5-0.95	AIMS

C. Criterion validity

Tested

Comparison with a 'gold standard' Continuous scores:
correlations, ROC curves Dichotomus:
Sensitivity & Specificity (Describe)

Validity testing of FIQ is hard to find good evidence because the fibromyalgia syndrome lacks the type of objective criteria (gold standard) available for some other rheumatic diseases such as rheumatoid arthritis. However, AIMS scale has been set as sort of gold standard, as it was being used since 1991 in other rheumatology pathologies. FIQ pain, depression, and anxiety visual analogs and GIF physical functioning item were all moderately to highly correlate with the comparable AIMS scales.

Based on Burkhardt (1991) paper the correlations between the items on the FIQ and the comparable scale of the AIMS are indicative of some degree of convergent construct validity of both instrument.

Items	Impact Analog (n=64)*	Syndrome activity (n=64)*	Tender points (n=13)***	Tender points (n=25)**
Physical function	0.30	0.49	0.40	0.61
Feel good	0.29	0.57	0.09	0.40
Work missed	0.17	0.47	0.64	0.74
Job ability	0.31	0.63	0.15	0.36
Pain	0.48	0.83	0.37	0.38
Fatigue	0.37	0.48	0.28	0.22
Morning tiredness	0.34	0.48	0.28	0.14
Stiffness	0.31	0.50	0.39	0.36
Anxiety	0.25	0.28	0.43	0.21
Depression	0.29	0.31	0.34	0.23

* All coefficients in these 2 columns are significant at the p=0.05 level with the exception of the score for work missed on the first column.

** First three coefficients in the column are statistically significant.

*** none of the coefficients in this column are statiscally significant.

1. Correlation analysis demonstrated that the FIQ physical functioning item had a highly significant correlation of .67 with the AIMS lower extremity physical functioning component.

2. Pain, depression and anxiety analog scales also showed highly correlations of 0.69, 0.73 and 0.76 with their respective AIMS scales.

In general, fibromyalgia patients have higher FIQ scores than patients with regional pain, chronic widespread pain, and migraine. In a study of post mastectomy pain, those patients with pain localized to the incisional site had a total FIQ score of 20.9 ± 13.2 compared to a score of 52.0 ± 15.1 (p<0.001) in patients describing widespread pain (BURCKARDTS, JONES K D: Effects of chronic widespread pain on the health status and quality of life of women after breast cancer surgery. Health Qual Life Outcomes 2005;3:30).

In a community study of 100 fibromyalgia patients compared to other pain conditions, the fibromyalgia patients had a total FIQ score of 61.2 compared to a score of 41.6 in patients with other pain conditions (p < 0.00001) (WHITE KP, SPEECHLEY M, HARTH M, OSTBY E T: Comparing self-reported function and work disability in 100 community cases of fibromyalgia syndrome versus controls in London, Ontario: the London Fibromyalgia Epidemiology Study. Arthritis Rheum 1999; 42: 76-83.)

Montoya (2001) studied the influence of social support and emotional context on pain processing and magnetic brain responses in 18 fibromyalgia patients and 18 controls who had migraine. The total FIQ score in fibromyalgia was 52.23 ± 17.87 versus 35.82 ± 26.28 in the migraine controls (< 0.01).