Osteocalcin, iPTH, Alkaline Phosphatase and Hand X-Ray Scores as Predictive Indices of Histomorphometric Parameters in Renal Osteodystrophy

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Abstract
To evaluate the relationship between hyperparathyroid bone X-ray lesion, biochemical parameters and bone histology in chronic renal failure, 59 patients (52 ± 14.9 years; Crs 4.7 ± 2.2 mg/dl, mean ± SD) on conservative treatment and 103 (48 ± 14 years) on hemodialysis (from 48.4 ± 36.7 months) were studied. Right-hand X-ray was carried out for evaluation of the scores (0–3) of acroosteolysis (score A) and subperiosteal resorption (score B). Serum iPTH, osteocalcin and alkaline phosphatase (AP) were measured. In addition in a subset of 53 patients, 30 in predialysis and 23 in dialysis, a bone biopsy was performed for histomorphometry. In predialysis the scores A and B correlated with bone GLA protein (BGP) (p < 0.001), iPTH (p < 0.01), AP (p < 0.05) and osteoid surface (p < 0.05 and 0.01 respectively). In hemodialysis the same level of significant correlation (p < 0.001) was found between the scores and the three humoral parameters. Score A correlated with active osteoblastic surface and active resorption surface while score B correlated with active osteoblastic surface (p < 0.01), osteoid surface and active resorption surface (p < 0.05). Multiple regression analysis carried out to establish the predictive variables of bone histologic lesions (active resorption surface and active osteoblastic surface) singled out BGP in predialysis and AP and the two scores in dialysis. We conclude that serum BGP, as compared to PTH and AP, prevails as a valid marker of hyperparathyroid bone lesion in predialysis, while in dialysis it does not seem to add further information to that carried by other variables. On practical grounds bone histology cannot be satisfactorily predicted by noninvasive methods, especially in hemodialysis.