CALCA and Arthritis: In addition, clinical studies of individuals, which are positive for anti-CCP antibodies, but have no arthritis or clinical symptoms yet, have shown that lesions with subclinical inflammation in bone and bone marrow (Matthijssen et al., 2019) or early erosions (Brinck et al., 2018; Wouters et al., 2020), which are detectable only by magnetic resonance imaging (MRI), often precede development of arthritis.