Validation of a Dutch translation of the fibromyalgia impact questionnaire.
OBJECTIVE
To validate a Dutch translation of the fibromyalgia impact questionnaire (FIQ).


METHODS
Data were taken from two randomized clinical trials on Spa treatment and venlafaxine in fibromyalgia (FM). Participants completed the Dutch FIQ and a set of validated questionnaires for general health (RAND-36), depression (Beck depression inventory, BDI), pain (McGill pain questionnaire, MPQ) and fatigue (checklist individual strength, CIS). Internal consistency within the FIQ item 'physical functioning' was studied using Cronbach's alpha. Test-retest reliability was studied with intra-class-correlation (ICC) in a subsample of 76 control subjects over a 3 month period without specific intervention. Construct validity was evaluated by correlating the FIQ to other questionnaires. Sensitivity to change was studied using standardized response means (SRM).


RESULTS
The study sample consisted of 213 women and 11 men (mean age 47 yrs, mean disease duration 11 yrs). Cronbach's alpha for the item 'physical functioning' was 0.91, indicating high internal consistency. Test-retest reliability was acceptable, with ICC ranging from 0.45 for 'morning tiredness' to 0.71 for 'physical function'. FIQ correlated significantly with the RAND-36, with Spearman's rho ranging from -0.60 to -0.70 for items measuring the same concept. Similar patterns of correlation were seen with MPQ, BDI and CIS. Sensitivity to change was sufficient, with SRM after Spa treatment ranging from 0.3 for 'work days missed' to 0.9 for 'days felt good'. Similar SRM were found in the venlafaxine trial for patients reporting general improvement.


CONCLUSIONS
The Dutch FIQ is a valid instrument for measuring health status in FM, showing sufficient reliability, construct validity and responsiveness.
Zijlstra
T R
TR
Department of Rheumatology, Medisch Spectrum Twente Hospital, The Netherlands. tr.zijlstra@worldonline.nl
Taal
E
E
van de Laar
M A F J
MA
Rasker
J J
JJ
D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D018687:Antidepressive Agents, Second-Generation / Q000627:therapeutic use; D001452:Balneology; D003431:Cross-Cultural Comparison; D003511:Cyclohexanols / Q000627:therapeutic use; D004311:Double-Blind Method; D005260:Female; D005356:Fibromyalgia / Q000534:rehabilitation* / Q000628:therapy; D006305:Health Status Indicators; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D000069470:Venlafaxine Hydrochloride
D018687:Antidepressive Agents, Second-Generation; D003511:Cyclohexanols; D000069470:Venlafaxine Hydrochloride