In addition, apolipoprotein A-I (ApoA1) and cholesterol were observed to increase in SF of RA patients, yet decreases in SF of OA patients and serum levels of ApoA1 and total cholesterol (TC) were higher in OA in comparison with RA, psoriatic arthritis and normal control group [96], suggesting these lipid and apolipoprotein factors can be regarded as possible OA markers. Here, APOA1 is linked to psoriatic arthritis.