MSTN and rheumatoid arthritis: The study performed by Murillo-Saich et al. found a myostatin cut-off point of ≥13 ng/mL to be a risk factor for presenting moderate/severe disease activity (OR = 2.93, 95% CI 1.13–7.61), with a sensitivity of 61%, indicating the possibility of positive myostatin results in patients with moderate/severe disease, and a specificity of 53%, indicating the possibility of negative myostatin results in RA patients with low activity/remission [61].