RESEARCH - Fatigue is a reliable, sensitive and unique outcome measure in RA

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Rheumatology Advance Access published online on September 22, 2009

Rheumatology, doi:10.1093/rheumatology/kep287

Fatigue is a reliable, sensitive and unique outcome measure in

rheumatoid arthritis

Minnock1, Kirwan2 and Barry Bresnihan1,3,4

1Rheumatology Rehabilitation, Our Lady's Hospice, Dublin, 2University

of Bristol Academic Rheumatology Unit, Bristol Royal Infirmary,

Bristol, 3St 's University Hospital and 4University College

Dublin, Dublin, UK.

Abstract

Objective. Fatigue is an important symptom in patients with RA.

Measurement of fatigue in clinical trials and in clinical practice

requires scales that are reproducible, sensitive to change and

practical. This study examined the reliability and sensitivity to

change of fatigue and its relative independence as an outcome measure

in RA.

Methods. Successive patients referred to the rheumatology clinic at St

's University Hospital and Our Lady's Hospice were evaluated.

Clinical assessments were undertaken at baseline and 3 months after

commencing TNF- blockade. Fatigue was measured using an 11-point

numeric rating scale (NRS). Sensitivity to change when compared with

current core set outcome measures was determined by calculation of the

standardized response mean (SRM). Multiple regression analysis was

employed to determine the independent variance of fatigue scores

relative to the core set.

Results. Forty-nine patients were evaluated. At baseline, mean (S.D.)

fatigue scores were 6.7 ± 2.1. At 3 months, fatigue scores had fallen

to 4.3 ± 2.6 (P < 0.001). Test–retest intraclass correlation

coefficient for the NRS was 0.79 (P < 0.008). Fatigue was ranked third

for relative sensitivity to change as shown by SRM: pain, 1.37; tender

joint count (TJC), 1.09; fatigue, 0.92; swollen joint count (SJC),

0.86; HAQ, 0.82; CRP, 0.69; and patient global health (GH), 0.25. The

relative independent variance in fatigue of 22% was higher than that

of the core set: TJC, 20%; pain, 19%; SJC, 16%; GH, 8%; HAQ, 7%; and

CRP, 8%.

Conclusions. This study demonstrates that measures of fatigue are

reliable and sensitive to change, and should be considered for

inclusion as a core outcome measure in RA.

http://rheumatology.oxfordjournals.org/cgi/content/abstract/kep287v1?papetoc

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