Standardized grip strength as an outcome measure in early rheumatoid arthritis

Abstract

Objectives: Patients with rheumatoid arthritis (RA) suffer progressive loss of hand function and have weaker hand grip than the healthy population. In this study we aimed to validate hand grip strength standardized by age and gender (z score) against currently accepted clinical measures of disease activity.

Method: Electronic records of patients with a diagnosis of RA seen between April 2007 and December 2011 were screened for the documentation of tender and swollen joint counts, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), along with patient global activity score and grip strength. Bilateral grip strengths were converted to z scores on the basis of previously published age- and gender-corrected normative data for grip strength. The z scores were then correlated against components of disease activity scores.

Results: Ninety patients diagnosed with RA had been seen 602 times within 2 years of diagnosis. Hand grip data were available for 204 visits. There was a statistically significant inverse correlation between grip strength z scores and the tested variables. The sensitivity and specificity of a hand grip z score of −1.5 for predicting remission were, respectively, 70% and 76% for the right hand and 82% and 69% for the left hand.

Conclusions: Hand grip testing and subsequent conversion to z scores corrected for age and gender correlate with disease activity in early RA. We have shown that the grip strength z scores can discriminate between various disease states, and the strength seems to return to near normative data when the disease is in remission.