i dont underdtand this Results The plasma vit D levels were 18 μg/L (8-38) in the AS group, 20 μg/L (4-92.3) in the uSpA group and 24.3 μg/L (7.2-76.8) in the control group. The plasma vit D levels of the AS patients were significantly lower than those of the patients in the control group (p=0.004). The men in the AS group had significanly lower vit D levels than those in the control group (p=0.005). On the other hand, the women in the uSpA group had significanly lower vit D levels than those in the control group (p=0.011). The vit D levels were inversely related to both erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in the AS patients (p=0.002, R=-0.428; p<0.001, R=-0.592, respectively). This correlation was not demonstrated in the uSpA patients. The vit D levels were not found to correlate with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) levels in either the AS or uSpA patients.