There is significant disagreement between the IDS-iSYS and Roche Cobas assays for both reference markers. Consequently, the reference intervals for an adult, healthy population are different depending on the analysis method used. Therefore, repeated measurements of patient samples used for monitoring of treatment should be done on the same assay. Moreover, assay-specific reference intervals should be used. Harmonization of assays for BTM is highly warranted.

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Background: In obesity, which is a major contributor to insulin resistance and diabetes, the circulating level of S100A8/A9 (calprotectin) is elevated and declines after Roux-en-Y gastric bypass surgery (RYGB). However, studies on S100A8/A9 and the pathophysiological mechanisms in insulin resistance and diabetes are few and contradictory. Methods: We studied 48 subjects who underwent RYGB, comprising a non-diabetic control group and two diabetic groups in whom diabetes either regressed or persisted, 6-12 months post-surgically. S100A8/A9, interleukin 6 (IL-6) as well as other inflammatory and diabetes-related markers were measured pre- and post-surgically. Results: Significant and similar decreases of BMI were found in all groups. S100A8/A9 and IL-6 decreased significantly in the group with diabetes remission and in the control group, but not in the group with persistent diabetes. The relative changes in S100A8/A9 and IL-6 correlated significantly (r = 0.905, p = 0.005) only in the group with persistent diabetes. In contrast, leukocyte count and C-reactive protein correlated significantly to S100A8/A9 only in the control group. Conclusion: Our study is suggestive of S100A8/A9 and IL-6 being related to a persistent diabetes status post-surgically and of different pathophysiological mechanisms being involved in the post-surgical changes in the three groups, despite similar decreases in BMI.

This longitudinal study examined associations of bone mass with physical activity and vitamin D level over more than 6 years through puberty. A total of 663 participants (320 boys) with mean age 9.6 years at baseline (10-17 years at follow-up), underwent dual energy X-ray absorptiometry, anthropometry and blood samples for vitamin D at least twice during the study period (with three possible time-points). Physical activity was assessed using accelerometers at follow-up. A positive association was found between percent time spent at vigorous physical activity and total-body less head bone mineral content (β = 5.8, p = 0.002). The magnitude of this association increased with maturational development; thus physical activity may have a greater influence on bone mass in the more mature participants. The vitamin D levels were also positively associated with bone mass. A high degree of tracking was observed with changes in anthropometric Z scores predictive of deviation from tracking. No environmental factor predicted deviation from tracking.

declare that they have no conflict of interest. Highlights  Insulin resistance was inversely associated with bone mass in adolescent boys  The association in boys was not explained by differences in body composition or physical activity levels  No association between insulin resistance and bone mass was observed in adolescent girls.

Bone mass is highly influenced by pubertal onset, and pubertal stage should be considered when examining children's bone health. Because bone mass indices track from childhood into puberty, children with low bone mass may be at risk of developing osteoporosis later in life.