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Bone-specific alkaline phosphatase concentrations are less variable than those of parathyroid hormone in stable hemodialysis patients.

Sardiwal S, Gardham C, Coleman AE, Stevens PE, Delaney MP, Lamb EJ - Kidney Int. (2012)

Bottom Line: The within-individual coefficients of variance were calculated and used to derive the critical difference required to be certain that an observed change was significant.The coefficient of variance for bone ALP was significantly higher in hemodialysis patients compared to healthy individuals.The concentration of serial bone ALP measurements would need to change by 36% between any two measurements before it can be considered a significant change.

View Article: PubMed Central - PubMed

Affiliation: Clinical Biochemistry, East Kent Hospitals University NHS Foundation Trust, Kent and Canterbury Hospital, Canterbury, UK.

ABSTRACT
Abnormalities of bone mineral metabolism and vascular calcification are prevalent in patients with kidney failure. Clinical management is based on biochemical targets, in particular parathyroid hormone (PTH) concentrations, but this has many limitations including high biological variation. A possible alternative is bone-specific alkaline phosphatase (ALP); therefore, we evaluated the biological variation of this marker in patients undergoing hemodialysis. Bone ALP was measured in non-fasting serum samples taken twice a week over a 6-week period in 22 stable hemodialysis patients and 12 healthy volunteers. The within-individual coefficients of variance were calculated and used to derive the critical difference required to be certain that an observed change was significant. The coefficient of variance for bone ALP was significantly higher in hemodialysis patients compared to healthy individuals. Seven samples were required to estimate the homeostatic set point of bone ALP, within 10%, in a hemodialysis patient. The concentration of serial bone ALP measurements would need to change by 36% between any two measurements before it can be considered a significant change. Since the biological variation of bone ALP is less than half that reported for PTH, our study provides further support for the use of bone ALP as an alternative marker of bone mineral metabolism in the setting of chronic kidney disease-mineral and bone disorder.

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Related in: MedlinePlus

A box plot showing median (horizontal line), upper, and lower quartile (large rectangle), as well as range (represented by the whiskers), for serum bone alkaline phosphatase (bALP) concentration for hemodialysis (HD) patients (subjects 1–22) and the healthy volunteers (subjects 23–34). The dashed lines represent the upper reference limit (22.4 μg/l) for the assay used. Note that study numbers are the same as in our previously published study,7 enabling direct comparison with parathyroid hormone (PTH) variability and concentrations within subjects.
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fig1: A box plot showing median (horizontal line), upper, and lower quartile (large rectangle), as well as range (represented by the whiskers), for serum bone alkaline phosphatase (bALP) concentration for hemodialysis (HD) patients (subjects 1–22) and the healthy volunteers (subjects 23–34). The dashed lines represent the upper reference limit (22.4 μg/l) for the assay used. Note that study numbers are the same as in our previously published study,7 enabling direct comparison with parathyroid hormone (PTH) variability and concentrations within subjects.

Mentions: Figure 1 shows the individual median and range concentrations for bone ALP in all the study subjects. The CVI for bone ALP was significantly higher for the hemodialysis patients compared with the healthy volunteers (P<0.05), resulting in a greater number of specimens being required to estimate an individual's homeostatic set point and a higher critical difference (Table 2). No significant difference (P>0.05) in the CVI for bone ALP was observed between those patients who underwent dialysis in the morning (12.9%) and those who underwent dialysis in the afternoon (12.2%).


Bone-specific alkaline phosphatase concentrations are less variable than those of parathyroid hormone in stable hemodialysis patients.

Sardiwal S, Gardham C, Coleman AE, Stevens PE, Delaney MP, Lamb EJ - Kidney Int. (2012)

A box plot showing median (horizontal line), upper, and lower quartile (large rectangle), as well as range (represented by the whiskers), for serum bone alkaline phosphatase (bALP) concentration for hemodialysis (HD) patients (subjects 1–22) and the healthy volunteers (subjects 23–34). The dashed lines represent the upper reference limit (22.4 μg/l) for the assay used. Note that study numbers are the same as in our previously published study,7 enabling direct comparison with parathyroid hormone (PTH) variability and concentrations within subjects.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376309&req=5

fig1: A box plot showing median (horizontal line), upper, and lower quartile (large rectangle), as well as range (represented by the whiskers), for serum bone alkaline phosphatase (bALP) concentration for hemodialysis (HD) patients (subjects 1–22) and the healthy volunteers (subjects 23–34). The dashed lines represent the upper reference limit (22.4 μg/l) for the assay used. Note that study numbers are the same as in our previously published study,7 enabling direct comparison with parathyroid hormone (PTH) variability and concentrations within subjects.
Mentions: Figure 1 shows the individual median and range concentrations for bone ALP in all the study subjects. The CVI for bone ALP was significantly higher for the hemodialysis patients compared with the healthy volunteers (P<0.05), resulting in a greater number of specimens being required to estimate an individual's homeostatic set point and a higher critical difference (Table 2). No significant difference (P>0.05) in the CVI for bone ALP was observed between those patients who underwent dialysis in the morning (12.9%) and those who underwent dialysis in the afternoon (12.2%).

Bottom Line: The within-individual coefficients of variance were calculated and used to derive the critical difference required to be certain that an observed change was significant.The coefficient of variance for bone ALP was significantly higher in hemodialysis patients compared to healthy individuals.The concentration of serial bone ALP measurements would need to change by 36% between any two measurements before it can be considered a significant change.

View Article: PubMed Central - PubMed

Affiliation: Clinical Biochemistry, East Kent Hospitals University NHS Foundation Trust, Kent and Canterbury Hospital, Canterbury, UK.

ABSTRACT
Abnormalities of bone mineral metabolism and vascular calcification are prevalent in patients with kidney failure. Clinical management is based on biochemical targets, in particular parathyroid hormone (PTH) concentrations, but this has many limitations including high biological variation. A possible alternative is bone-specific alkaline phosphatase (ALP); therefore, we evaluated the biological variation of this marker in patients undergoing hemodialysis. Bone ALP was measured in non-fasting serum samples taken twice a week over a 6-week period in 22 stable hemodialysis patients and 12 healthy volunteers. The within-individual coefficients of variance were calculated and used to derive the critical difference required to be certain that an observed change was significant. The coefficient of variance for bone ALP was significantly higher in hemodialysis patients compared to healthy individuals. Seven samples were required to estimate the homeostatic set point of bone ALP, within 10%, in a hemodialysis patient. The concentration of serial bone ALP measurements would need to change by 36% between any two measurements before it can be considered a significant change. Since the biological variation of bone ALP is less than half that reported for PTH, our study provides further support for the use of bone ALP as an alternative marker of bone mineral metabolism in the setting of chronic kidney disease-mineral and bone disorder.

Show MeSH
Related in: MedlinePlus