RESUMO
AIM: The objective of this study was to examine the time-varying relationship of chronic kidney disease-mineral bone disorder (CKD-MBD) related biochemical parameters (parathyroid hormone (PTH), calcium, phosphate) over a 12-month period. MATERIAL AND METHODS: Using data from a large US provider of dialysis services from 2010 through 2012, we constructed a cohort of adult patients receiving in-center hemodialysis who had biochemical parameters measured at both baseline and 12 months of follow-up. We used descriptive statistics to assess the overall distributions of the biochemical parameters at both measurements, to examine how patients transitioned between categories for each biochemical parameter, and to evaluate how the biochemical parameters changed with respect to each other. RESULTS: Among the 132,087 patients included in our analyses, the cross-sectional distributions for the combined categories of 150 - < 300 and 300 - < 600 pg/mL for PTH between the two measurements remained unchanged (67% of patients). For calcium and phosphate, the distributions across all categories also remained largely unchanged. Considering within-patient changes over time. however, a majority (74%) of patients who initially had a PTH < 150 pg/mL transitioned to a higher category, while a majority (56%) of patients who initially had a PTH > 600 pg/mL transitioned to a lower category. We observed that phosphate values on average directly trended with PTH values over the follow-up period. CONCLUSION: We found that while calcium showed relatively little variation, parallel bidirectional variation in PTH and phosphate over time was quite common among adult patients receiving hemodialysis. Optimal control of phosphate is likely to be dependent not only on consistent adherence to dietary restrictions and phosphate binders, but may additionally rely on adequate and sustained control of PTH.