Validation of grip strength as a measure of frailty in rheumatoid arthritis

Rheumatoid arthritis (RA) patients often exhibit finger/wrist joint symptoms and reduced grip strength. This study aimed to validate grip strength as a measure of frailty in RA patients. Subjects were 424 female RA patients (mean age ± standard deviation, 66.8 ± 14.5 years). Frailty was defined as a score of ≥ 8 points on the Kihon Checklist (KCL). Finger/wrist joint symptoms were defined based on tender or swollen joints. Associations between frailty and grip strength were determined using receiver operating characteristic (ROC) curve analysis and multivariable logistic regression analysis. There were 179 subjects with frailty (42.2%). Multivariable logistic regression analysis revealed that frailty was significantly associated with grip strength independently of finger/wrist joint symptoms. In ROC curves, cut-off scores of grip strength for frailty in subjects without and with finger/wrist joint symptoms were 17 kg (sensitivity, 62.1%; specificity, 69.0%) and 14 kg (sensitivity, 63.2%; specificity, 73.0%), respectively. The results of the present study suggest that grip strength in female RA patients is associated with frailty, with a cut-off score of 17 kg (equivalent to Cardiovascular Health Study criteria, < 18 kg) when RA patients have no finger/wrist joint symptoms. However, when RA patients have finger/wrist joint symptoms, it may be considered to reduce the cut-off score of grip strength.