Osteoporosis is a disease characterized by low bone density and a deterioration of bone microarchitecture that reduces bone strength and increases the risk of fracture. The hallmark of osteoporosis is the loss of both bone mineral and bone matrix. Although Bone mass density (BMD) is still the gold standard for the diagnosis of osteoporosis, but bone turnover markers (BTMs) can provide helpful information regarding the bone remodelling process. One of these relatively recent markers is the Tartrate-resistant acid phosphatase (TRACP). TRACP, which was first identified in human leukocytes, has 2 isoforms TRAP-5a derived from macrophages and dendritic cells and TRACP-5b secreted by osteoclasts. it is believed that TRACP-5b is a useful marker of osteoclast activity, even a marker for osteoclast number, as it is associated with osteoclast differentiation, activation and proliferation. Furthermore, it has the advantage of not being affected by renal dysfunction, nor food intake and has a weak diurnal variability. And this is why it has been used as one of the bone turnover markers in evaluating the efficacy of different anti-resorptive treatments in postmenopausal osteoporosis and in 2ry OP due to rheumatoid arthritis as well as in evaluating its specificity in identification of postmenopausal OP when compared to measurement of more expensive, relatively unavailable bone mineral density (BMD).So far, limited researches are available regarding the TRACP-5b level difference among 1ry OP (postmenopausal women) and 2ry OP (ex. RA, SpA).
Assessment of the TRACP-5b level in 1ry OP and 2ry OP such as RA and seronegative spondylitis, that may help in surrogating the use of BMD.