The Revised Fibromyalgia Impact Questionnaire (FIQR): validation and psychometric properties

Abstract

Introduction: The Fibromyalgia Impact Questionnaire (FIQ) is a commonly used instrument in the evaluation of fibromyalgia (FM) patients. Over the last 18 years, since the publication of the original FIQ, several deficiencies have become apparent and the cumbersome scoring algorithm has been a barrier to widespread clinical use. The aim of this paper is to describe and validate a revised version of the FIQ: the FIQR.

Methods: The FIQR was developed in response to known deficiencies of the FIQ with the help of a patient focus group. The FIQR has the same 3 domains as the FIQ (that is, function, overall impact and symptoms). It differs from the FIQ in having modified function questions and the inclusion of questions on memory, tenderness, balance and environmental sensitivity. All questions are graded on a 0-10 numeric scale. The FIQR was administered online and the results were compared to the same patient's online responses to the 36-Item Short Form Health Survey (SF-36) and the original FIQ.

Results: The FIQR was completed online by 202 FM patients, 51 rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) patients (31 RA and 20 SLE), 11 patients with major depressive disorder (MDD) and 213 healthy controls (HC). The mean total FIQR score was 56.6 +/- 19.9 compared to a total FIQ score of 60.6 +/- 17.8 (P < 0.03). The total scores of the FIQR and FIQ were closely correlated (r = 0.88, P < 0.001). Each of the 3 domains of the FIQR correlated well with the 3 related FIQ domains (r = 0.69 to 0.88, P < 0.01). The FIQR showed good correlation with comparable domains in the SF-36, with a multiple regression analysis showing that the three FIQR domain scores predicted the 8 SF-36 subscale scores. The FIQR had good discriminant ability between FM and the 3 other groups; total FIQR scores were HC (12.1 +/- 11.6), RA/SLE (28.6 +/- 21.2) and MDD (17.3 +/- 11.8). The patient completion time was 1.3 minutes; scoring took about 1 minute.

Conclusions: The FIQR is an updated version of the FIQ that has good psychometric properties, can be completed in less than 2 minutes and is easy to score. It has scoring characteristics comparable to the original FIQ, making it possible to compare past FIQ results with future FIQR results.

Figure 1

Histograms of FIQ and FIQR showing distributions of total scores. (a) The distribution profile of the total Revised Fibromyalgia Impact Questionnaire (FIQR) scores in 202 fibromyalgia (FM) patients. (b) The distribution profile of the total Fibromyalgia Impact Questionnaire (FIQ) scores. There is a slight negative skewness for both distributions. The FIQR Shapiro-Wilk skewness coefficient (W) is 0.978, and the FIQ Shapiro-Wilk skewness coefficient (W) is 0.980.

Figure 2

A scatterplot of the total score for the Revised Fibromyalgia Impact Questionnaire (FIQR) and the Fibromyalgia Impact Questionnaire (FIQ) on all 202 fibromyalgia subjects (r = 0.88, P < 0.001).

Figure 3

The total Revised Fibromyalgia Impact Questionnaire (FIQR) scores of the 202 fibromyalgia (FM) patients compared with the scores for the 213 healthy controls, 51 patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE), and 11 patients with major depression. *Note: a concomitant diagnosis of FM was an exclusion criterion for inclusion of RA/SLE and major depressive disorder (MDD) subjects. SE, standard error.

Figure 4

A plot of the mean scores for the four new symptoms added to the Revised Fibromyalgia Impact Questionnaire (memory, tenderness, balance, and environmental sensitivity) against each of the four groups: fibromyalgia (FM), rheumatoid arthritis/systemic lupus erythematosus (RA/SLE), healthy, and major depressive disorder (MDD).