Background/Purpose: Rheumatoid arthritis (RA) is
characterized by inflammation of the joints and fatigue. Although many studies
have identified risk factors for RA-associated fatigue, few studies have comprehensively
examined the role of C – reactive protein (CRP) on fatigue. We investigated the
association of CRP on fatigue using the Patient Reported Outcomes Measurement
Information System (PROMIS) in a cohort of patients with RA.

Methods:
 RA
subjects enrolled in the University of Pittsburgh Rheumatoid Arthritis
Comparative Effectiveness Registry (RACER) and who completed the PROMIS29
questionnaire were included (N=180). RA specific risk factors (disease activity
measured by the Clinical Disease Activity Index [CDAI], physical function, RA
treatment [conventional Disease Modifying Anti-Rheumatic Drugs (DMARD), anti –
tumor necrosis factor [TNF], other biologics, disease duration, pain level),
non-RA risk factors (sleep, anxiety, depression, Charlson comorbidity index) as
well as CRP  were assessed using descriptive statistics to summarize the
distribution of the variables. Fatigue identified by PROMIS29 was the primary
outcome.  Spearman correlations and univariate analyses were first conducted
to evaluate associations with fatigue. Multiple linear regression analyses were
performed to investigate whether CRP is an independent predictor of fatigue.
Mediation analysis was performed to explore if there is any indirect
relationship between CRP level and factors associated with fatigue.

Results:   Mean (±SD) subject age was 63.9
(±12.2) years with disease duration of 7.7 (± 0.8) years. Univariate analyses
identified 7 covariates (age, CDAI score, global pain intensity, physical
function, sleep, anxiety, depression) initially as potential predictors of
fatigue. In multivariate analyses, physical function, sleep, and depression
were independently associated with fatigue, but CRP or RA treatments did not
have significant association with fatigue. (Table.1) CRP was inversely
correlated with physical function (ρ
= -0.23, p=0.016). However, there was no mediation effect between CRP and
physical function in association with fatigue.

Conclusion:    Out study suggests
that poor sleep, decreased physical function, and depression have significant
effect on fatigue. CRP level was not associated with fatigue directly or
indirectly.