SERUM BONE ALKALINE-PHOSPHATASE IS SUPERIOR TO PLASMA-LEVELS OF BONE-MATRIX PROTEINS FOR ASSESSMENT OF BONE METABOLISM IN PATIENTS RECEIVING RENAL-TRANSPLANTS

The plasma concentrations of two bone matrix proteins (osteocalcin, os teonectin) were monitored in 56 samples from 14 patients receiving ren al transplants and the values compared with serum bone alkaline phosph atase mass concentrations and osteotropic hormone levels (parathyroid hormone, calcitriol). There were no significant changes in the concent rations of plasma osteonectin at any time after transplantation, as co mpared with the values before transplantation (P > 0.1). None of the p lasma samples showed osteonectin levels above the reference interval. There was a weak but significant relationship between platelet counts and plasma osteonectin levels (r = + 0.322; P < 0.05). Osteocalcin sho wed a marked decrease of the values 1 week following transplantation a s compared with the values before transplantation without further chan ge of the values 1 and 3 months after transplantation (P > 0.5) wherea s 3 months after transplantation bone alkaline phosphatase levels were higher than before transplantation (P < 0.05). Multiple regression an alysis (performed with data from 42 samples obtained after transplanta tion) revealed serum creatinine as an independent predictor of plasma osteocalcin whereas serum calcitriol was an independent predictor of s erum bone alkaline phosphatase (P < 0.05). No correlation was observed between serum calcitriol/plasma parathyroid hormone on the one hand a nd plasma osteocalcin on the other (P > 0.05). After transplantation t here was a lack of correlation between serum bone alkaline phosphatase mass concentrations and plasma osteocalcin values (P > 0.05). In conc lusion, serum bone alkaline phosphatase should be preferred to bone ma trix proteins for the assessment of bone metabolism in patients receiv ing renal transplants: (a) bone alkaline phosphatase - but not osteoca lcin - is significantly correlated with calcitriol and adequately refl ects increased bone formation after renal transplantation; (b) interpr etation of osteocalcin values is severely hampered by their strong cor relation with serum creatinine concentrations; (c) plasma osteonectin determinations are not useful for monitoring bone formation. (C) 1997 Elsevier Science B.V.