Objective:
To investigate the feasibility of bone turnover markers (BTMs) for the assessment of bone metabolism in patients with systemic lupus erythematosus (SLE), according to the guidelines of the International Osteoporosis Foundation and the International Federation of Clinical Chemistry and Laboratory Medicine.
Methods:
The study included 43 female SLE patients. Serum pro-collagen type I N propeptide (PINP), C-terminal telopeptide of type I collagen (CTX), osteocalcin, PTH, 25(OH)D, anti-cardiolipin, anti-dsDNA, and anti-nucleosome levels were measured.
Results:
PINP and CTX levels were elevated in SLE patients aged > 45 in comparison to those aged < 45, although with borderline significance (p = 0.05, respectively). Correlations were found between BTMs: the strongest being between PINP and osteocalcin (τ= 0.69, p < 0.05). PINP and osteocalcin were found to be associated with PTH (τ = 0.3, τ = 0.29, respectively, p < 0.05). Age correlated with PINP (τ= 0.23, p < 0.05). Elevated PINP was found more frequently than elevated osteocalcin or CTX, both in patients aged < 45 (p = 0.001) and > 45 (p < 0.001). No significant difference in PINP, osteocalcin or CTX levels was found with respect to season, neither in the entire SLE group, nor in the under-45 or over-45 groups. Previous glucocorticoid treatment was not associated with difference in BTMs.
Conclusions:
Increased BTMs in SLE appear to predominantly reflect the pattern of bone remodeling related to age. Increased PINP is expected to be the most frequent outcome among BTMs. Better diagnoses of bone disturbances with BTMs performed in accordance with international reference standards need to be included in the approach to SLE patients, in addition to bone mineral density assessment.
Bone turnover; Systemic lupus erythematosus; Procollagen; Osteocalcin; Vitamin D
