Concurrent validity of handgrip strength between the jamar and bulb dynamometers in women with rheumatoid arthitis

Abstract Introduction: Rheumatoid arthritis (RA) is a progressive disease that causes deformation and constant joint damage. Handgrip strength (HGS) has been used by several health professionals in clinical practice as a mechanism for assessing muscle strength and overall performance. Objective: To perform the concordance analysis of handgrip strength measurements using a pneumatic dynamometer (Bulb) and a hydraulic dynamometer (Jamar) in women with rheumatoid arthritis. Method: The HGS measurements by the two dynamometers followed the norms of the American Society of Hand Therapists. The concordance between measurements was performed by the Bland-Altman method. Significance level was 5%. Results: In total, 41 women (60.63 ± 8.35 years) participated in the study. Analysis showed that the measures between the two dynamometers were not concordant (bias = 9.04, p < 0.01), there was a linear relationship between the difference of the measures and the mean (r = 0.73, p < 0.01), and the limits of agreement were very extensive (−2.74 to 20.81). Conclusion: Assuming that the rheumatoid arthritis compromises the hands, with a consequent decrease in HGS, further exploration of the subject is suggested in future studies to define the best measure for clinical practice at the different levels of health care. However, since there are many different dynamometers, we suggest to better explore the agreement between the measurements obtained by them in populations under different conditions.