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Bone isoenzyme of serum alkaline phosphatase and serum inorganic phosphate in metabolic bone disease of prematurity
Author(s) -
Backström MC,
Kouri T,
Kuusela AL,
Sievänen H,
Koivisto AM,
Ikonen RS,
Mäki M
Publication year - 2000
Publication title -
acta paediatrica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 115
eISSN - 1651-2227
pISSN - 0803-5253
DOI - 10.1111/j.1651-2227.2000.tb00395.x
Subject(s) - medicine , alkaline phosphatase , bone mineral , endocrinology , metabolic bone disease , bone density , forearm , bone disease , dual energy x ray absorptiometry , phosphate , chemistry , surgery , biochemistry , osteoporosis , enzyme
We wanted to improve detection of low bone mineral density in preterm infants by combining serum measurements of total alkaline phosphatase, its bone‐type isoenzyme and serum inorganic phosphate in a prospective design. The subjects were 43 preterm infants. Total and bone isoenzyme activity of alkaline phosphatase was determined at 3 wk chronological age and at 3 and 6 mo corrected age. The main outcome measure, apparent bone mineral density (BMAD) at the distal forearm and forearm shaft, was assessed by dual energy X‐ray absorptiometry at 3 and 6 mo corrected age. An apparent density below 95 mg/cm 3 at 3 mo corrected age was considered to indicate bone disease, based on the distribution of BMAD values of children with non‐complicated courses of prematurity. At 3 mo corrected age, total alkaline phosphatase activities exceeding 900 IU/l revealed low bone mineral density with 88% sensitivity and 71% specificity. Measurements of bone isoenzyme activity did not improve diagnostic performance. Serum inorganic phosphate levels below 1.8 mmol/l reflected low bone density with high specificity (96%), but the sensitivity was only 50%. Conclusion: A combination of the criteria “serum total alkaline phosphatase activity above 900 IU/l” and “serum inorganic phosphate concentrations below 1.8 mmol/l” yielded a sensitivity of 100% at a specificity of 70%. This was the best available screening method for low bone mineral density in preterms.