Background Rheumatoid arthritis (RA) is a chronic inflammatory disease that primarily affects the joints, leading to disability. There are tools such as the HAQ for assessing the patient's disability but few studies associate this parameter to objective measurements. Biomechanical studies are an effective tool for determining functional capacity, so it would be useful to correlate them with other disability evaluation tools such as HAQ, as well as disease activity parameters.
Objectives To analyze the correlation between biomechanical studies of the hand with disability, disease activity and structural damage in RA patients.
Methods We have included 81 RA patients. The DAS28 score was used as a measure of disease activity and HAQ as a disability indicator, evaluated at the same time as the biomechanical study. Structural damage was measured using the Van der Heijde-Sharp score. Hand muscle strength was measured with a hand-held dynamometer. The data were analyzed using linear regression, robust regression and logistic regression.
Results We included 81 RA patients with DAS28 scores ranging between 1.25 and 7.61, and HAQ scores between 0 and 3. The erosion score was 0-51 (mean of 0 for both hands) and grip strength between 0-52 (means of 6 for right hand and 4 for the left). Using a biomechanical assessment, the disability and relative strength index (RSI) percent values are shown in the table.
Biostatistical analysis shows that for every point that the HAQ increases in the hand, there is an increase of about 5% in RSI and 2% in percentage of disability with a p-value less than 0.0001. There is also a statistically significant direct relationship between the increase in the DAS28 score and increasing LSI and hand disability. In addition, a statistically significant positive relationship is seen between LSI and disability, with structural damage, grip strength and erosions in the hand.
Conclusions There is a direct relationship between increased disability as assessed by biomechanical parameters with increasing HAQ scores, as well as disease activity and structural damage in RA patients. This result shows that disability can be measured more objectively in clinical practice since there is a correlation between the HAQ score, disease activity and structural damage to the hand on biomechanical measurements.
Disclosure of Interest None declared