Serum crosslaps in comparison to serum osteocalcin and urinary bone resorption markers

In this study we evaluated the routine practice and clinical application of serum crosslaps to urinary-crosslaps. -N-telopeptide-related fraction of t ype 1 collagen, -deoxpyridinoline, -totalpyridinoline and serum osteocalcin . The utility of both the serum and urine immunoassays for bone formation a nd resorption marker were rested in a cohort of 593 female and male patient s from our outpatient clinic for osteology and rheumatology and compared to important osteoporosis risk factors like age, gender, E2 deficiency, bone density and chronic renal failure. The biochemical maker of bone formation, serum osteocalcin exhibit signific ant correlations to all five tested serum and urinary markers of bone resor ption (p < 0.0001) crosswise to all different groups of patients. The group of chronic renal failure patients showed no significant correlati on between the tested bone turnover parameters and the serum creatinine lev el except a significant increase and correlation for serum crosslaps and fo r the ratio of serum and urinary crosslaps. Associations between the age of the patients and the markers of bone turnover were rather poor. We found a significant, negative association between serum and urinary bone turnover markers and bone density and were interested, whether in patients with bone density < 2.5 SD an enhanced bone turnover could be detected in the same way as for E2 deficiency. Applying a discriminant analysis it was possible to discriminate between the patient with ED < 2.5 SD and those wit h ED > 1.0 SD with a sensitivity of 70% and a specificity of 65% using seru m crosslaps. In case of urinary crosslaps the discriminatory power was slig htly lower (sensitivity: 65.6%, specificity: 67.5%) and for serum osteocalc in the discriminatory power was negligible higher (sensitivity: 79%, specif icity: 56%). The highly significant correlation between the urinary and serum crosslinke d peptides by ELISA and serum osteocalcin supports the concept that these r espective indices of bone formation and resorption both in urine and serum reflect a coupled process in vivo with sensitivity and specificity to patho logical bone density, estrogen deficiency and chronic renal failure. (C) 20 01 The Canadian Society of Clinical Chemists. All rights reserved.