Background There is some data to suggest that bone mineral density is lower in patients with ankylosing spondylitis. The mechanism could be increased matrix metalloproteinase 3 (MMP-3) activity and/or lower inhibitor levels (TIMP).
Objectives To compare bone mineral density of ankylosing spondylitis patients with published Indian standards. Also to compare MMP-3/TIMP ratio with controls.
Methods Patients who fulfilled modified New York criteria and gave consent were recruited. Bone mineral density was done using a Hologic DXA system. These were compared to published Indian standards (ICMR) of healthy young individuals (1). Levels of MMP-3 and TIMP in serum were determined using ELISA in both patients as well as 20 healthy controls (RnD Duo Set). Statistical analysis was done by using student t test for difference in means, correlation by pearsons correlation. Values are in mean (±SD).
Results 48 patients (M: F=46:2) of ankylosing spondylitis with age 33.7 (±10.1) years were enrolled. Disease duration was 11.2 (±6.0) years and duration of diagnosis 3.3 (±4.1) years. Mean BASDAI was 3.5 (±2.0), BASFI 3.2 (±2.3) and BASMI 2.3 (±2.3). Bone mineral density in patients compared to published Indian standards was not different in the spine (0.907±0.39, 0.976±0.105g/cm2, p=0.34) or forearm (0.604±0.063, 0.611±0.052 g/cm2, p=0.35) but was lower in the hip (0.846±0.130, 0.988±0.131 g/cm2, p=0.02). In patients as compared to controls, both serum MMP-3 (90.5±95.8, 55.9±37.1 ng/ml, p=0.04) and TIMP levels were higher (622.8±551.1, 296.5±114.2 ng/ml, p<0.001). However, there was no difference in the MMP-3/TIMP ratio (0.20±0.22, 0.20±0.14, p=0.95). Among patients, there was a negative correlation between the BMD of the hip and MMP/TIMP (r=-0.29, p=0.04) and BMD of forearm with MMP3/TIMP (r=-0.43, p=0.002). But there was a positive correlation with the BMD spine (r=0.41, p=0.003). There was no significant correlation between the ESR or BASDAI with MMP-3, TIMP or MMP-3/TIMP ratio.
Conclusions There is mild reduction of bone mineral density only in the hip in patients of ankylosing spondylitis compared to published Indian standards. Although both MMP-3 and TIMP are higher in patients, there is no difference in the MMP3/TIMP ratio compared to controls.
New Delhi: ICMR: Published by Director General; 2010. Population based reference standards of Peak Bone Mineral Density of Indian males and females – an ICMR multi-center task force study; pp. 1–24.
Disclosure of Interest None Declared