Feasibility of measurement of bone turnover markers in female patients with systemic lupus erythematosus

Abstract

ObjectiveTo investigate the feasibility of bone turnover markers for the assessment of bone metabolism in patients with systemic lupus erythematosus, according to the guidelines of the International Osteoporosis Foundation and the International Federation of Clinical Chemistry and Laboratory Medicine. MethodsThe study included 43 female systemic lupus erythematosus patients. Serum procollagen type I N propeptide, C-terminal telopeptide of type I collagen, osteocalcin, parathyroid hormone, 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3, anti-cardiolipin, anti-dsDNA, and anti-nucleosome levels were measured. ResultsProcollagen type I N propeptide and C-terminal telopeptide of type I collagen levels were elevated in systemic lupus erythematosus patients aged >45 in comparison to those aged <45, although with borderline significance (p=0.05, respectively). Correlations were found between bone turnover markers: the strongest being between procollagen type I N propeptide and osteocalcin (τ=0.69, p<0.05). Procollagen type I N propeptide and osteocalcin were found to be associated with parathyroid hormone (τ=0.3, τ=0.29, respectively, p<0.05). Age correlated with procollagen type I N propeptide (τ=0.23, p<0.05). Elevated procollagen type I N propeptide was found more frequently than elevated osteocalcin or C-terminal telopeptide of type I collagen, both in patients aged <45 (p=0.001) and >45 (p<0.001). No significant difference in procollagen type I N propeptide, osteocalcin or C-terminal telopeptide of type I collagen levels was found with respect to season, neither in the entire systemic lupus erythematosus group nor in the under-45 or over-45 groups. Previous glucocorticoid treatment was not associated with difference in bone turnover markers. ConclusionsIncreased bone turnover markers in systemic lupus erythematosus appear to predominantly reflect the pattern of bone remodeling related to age. Increased procollagen type I N propeptide is expected to be the most frequent outcome among bone turnover markers. Better diagnoses of bone disturbances with bone turnover markers performed in accordance with international reference standards need to be included in the approach to systemic lupus erythematosus patients, in addition to bone mineral density assessment.