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Article Review/Hyperlink
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Urena P, Hruby M, Ferreira A, Ang KS, de Vernejoul MC
Plasma total versus bone alkaline phosphatase as markers of
bone turnover in hemodialysis patients
J Am Soc Nephrol
(Mar) 7:506-512 1996

The authors investigated whether bone specific alkaline phosphatase
could differentiate patients with high bone turnover from those with
low turnover. Evaluation of 42 chronic hemodialysis patients included
plasma determinations of intact parathyroid hormone (IRMA- Nichols
assay), total alkaline phosphatase (automated method), and bone
specific alkaline phosphatase (IRMA, Ostase-Hypritech, Belgium), as
well as a transiliac bone biopsy for quantitative histomorphometry.
Patients were separated into groups according to type of bone disease
observed on biopsy; high turnover, normal or low-turnover, and
adynamic. Thirty-two patients had a high turnover lesion, while 1 had
adynamic bone disease and 9 had normal or low turnover lesion. Those
with high turnover had significantly higher plasma bone alkaline
phosphatase and PTH levels than those with normal or low turnover
disease whereas total alkaline phosphatase was not significantly
different between the 2 groups. Bone formation and resorption were
highly correlated with all the biochemical parameters, however, bone
alkaline phosphatase was better correlated with bone formation rate
than the total alkaline phosphatase and PTH. Plasma bone alkaline
phosphatase level greater than 20 ng/mL had the best sensitivity,
specificity and predictability for the diagnosis of high turnover bone
disease. The combination of a bone alkaline phosphatase greater than
20 ng/mL and PTH greater than 200 pg/mL essentially excluded patients
with normal or low turnover bone disease.
Comment: Despite the improvement of PTH assays and the
development of newer markers of bone formation and resorption, many
patients still require bone biopsy for diagnosis of their bone
disorder and help direct therapy. The recent development of
monoclonal antibodies against bone-specific alkaline phosphatase has
resulted in the development of sensitive immunoassays for
bone-specific alkaline phosphatase which has been demonstrated to be a
more reliable marker of bone turnover than total alkaline phosphatase.
Utilizing a newly developed IRMA assay for bone alkaline phosphatase
the authors demonstrated increased specificity and sensitivity of this
marker for differentiating high from low turnover in a group of
dialysis patients. Although bone alkaline phosphatase may become
useful for clinical use, its widespread application could not be
justified from this study. Only 10 of the patients evaluated had
normal or low turnover. Of these 10, 7 had IRMA PTH levels less 150
pg/mL, levels in which vitamin D therapy is usually initiated and a
biopsy would generally not be indicated as these patients would have
normal or decreased bone turnover. As indicated by a recent report by
Malluche and colleagues
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