EFFICACY OF SIMULTANEOUS DETERMINATION OF BONE ALKALINE-PHOSPHATASE MASS CONCENTRATION IN SERUM AND URINARY-EXCRETION OF PYRIDINIUM CROSS-LINKS FOR DETECTION OF BONE METASTASES

Objectives: To examine the diagnostic validity of bone alkaline phosph atase (BAP) in serum (a marker of bone formation) and of urinary excre tion of pyridinium cross-links (PYR) (a marker of bone resorption) for detection of bone metastases. Design and Methods: Two heterogeneous i mmunoassays were employed for determination of BAP mass concentrations (Tandem(R)-R Ostase(TM)) in serum and urinary excretion of PYR (Colla gen Crosslinks(TM)) in a consecutive series of 89 tumor patients exami ned by bone scintigraphy with Tc-99m-methylene diphosphonate). Results : The discrimination power (as determined by Z score analysis) and the accuracy (as assessed by the area under the receiver-operating charac teristic curve) was higher for BAP (0.84) than for PYR (0.76). Combina tion of both markers yielded a further increase of accuracy (0.89). Th ere was a correlation (r = +0.422; p < 0.001) between the urinary excr etion of pyridinium cross-links and bone alkaline phosphatase mass con centrations in the whole 89 patients examined. In 14 (16%) of 89 patie nts bone alkaline phosphatase values were within the reference interva l in spite of total alkaline phosphatase activity being increased; thi s indicates a higher diagnostic specificity of bone alkaline phosphata se (compared with total alkaline phosphatase) with respect to detectio n of bone metastases. Conclusions: Simultaneous assessment of bone for mation by BAP and of bone resorption by PYR provides a suitable tool f or detection of bone metastases.