Background In studies of rheumatoid arthritis (RA), patient reported outcomes or surrogate variables, such as radiographic joint damage, are often used as long term endpoints. Assessment of objective measures of function, such as standardized grip force evaluation, may be an important addition to longitudinal RA studies.

Objectives To investigate grip force in patients with early RA, compare this to age- and sex specific reference values, and assess changes over time.

Methods An inception cohort of patients with early RA (symptom duration <12 months), recruited in 1995-2005 from a defined area, was investigated. Patients were followed according to a structured program, with follow-up visit at 6, 12 and 24 months, as well as 5 and 10 years after inclusion. The clinical examinations were performed by the same rheumatologist. Grip force (newtons, N) was measured using the electronic instrument Grippit (AB Detektor, Gothenburg, Sweden). For the present study, peak grip force values of each hand were evaluated and compared to the expected, based on age- and sex-specific reference values from healthy subjects in the literature (1). The paired t-test was used for this comparison and for analysis of changes in grip force between visits.

Results A total of 223 patients with early RA (71% women, mean age 60 years, 62% RF positive, 57% anti-CCP2 positive) were investigated. At baseline, the mean peak grip force was 128.4 N [standard deviation (SD) 91.2] for the right hand and 122.5 N (SD 83.8) for the left hand, which was significantly lower than the corresponding expected values [306.4 N (SD 95.4) (p<0.001), and 294.4 (SD 95.4) (p<0.001)]. Similar grip force impairment compared to the expected was noted in males and females. Patients were managed according to usual care, with no pre-specified protocol for pharmacotherapy or rehabilitation. Low disease activity (LDA; DAS28<3.2) was attained in 47% at 5 years, and 25% were in clinical remission (DAS28<2.6). Grip force improved significantly from inclusion to the 12 month visit [mean change: 36.1 N; 95% confidence interval (CI) 26.6 -45.6 for the right hand, and 30.2 N; 95% CI 21.3-39.1 for the left hand], but there was no consistent change between the 1-year and 5-year follow-up evaluations (mean change: 5.1 N; 95% CI -7.7 to 18.0, and 7.0 N (95% CI -5.3 to 19.4, respectively) or through the 10-year visit. At 5 years, grip force in the right hand was lower than expected overall (mean 168.0 N vs 284.2 N; p<0.001) and also among those in LDA (mean 218.7 N vs 305.7 N; p<0.001), and those in clinical remission (mean 251.2 N vs 320.5 N; p=0.008). Similar differences were observed for the left hand at 5 years.

Conclusions In this study of early RA, grip force improved during the first year and remained stable thereafter. Patients in LDA or clinical remission at 5 years still had significantly reduced grip force. This suggests that further efforts to improve hand function are important in early RA.

References

1. Nilsen T et al. Scand J Occup Ther 2012;19:288-296.

Disclosure of Interest None declared