Urinary free deoxypyridinoline by chemiluminescence immunoassay: analytical and clinical evaluation

¹ Department of Pathology and Laboratory Medicine, Division of Laboratory Medicine, Albany Medical College, Albany, NY 12208.

² Clinical Biochemistry, Freeman Hospital, Newcastle upon Tyne NE7 7DN, United Kingdom.

³ Henry Ford Hospital, Detroit, MI 48202.

⁴ Department of Medicine, Division of Endocrinology and Metabolism, University of Heidelberg, Bergheimerstrasse 58, D-69115 Heidelberg, Germany.

⁵ Musculo Skeletal Unit, Freeman Hospital, Newcastle upon Tyne NE7 7DN, United Kingdom.
^a Author for correspondence. Fax 518-262-4337.

We evaluated an automated chemiluminescence immunoassay (CLIA) developed for the measurement of urinary free deoxypyridinoline (DPD). The new DPD method by CLIA is based on the competition of DPD with particle-bound pyridinoline for a limited amount of monoclonal mouse anti-DPD antibody. Total imprecision (CV) was 3.2–9.0% at 30–270 nmol/L. Regression analysis of urinary DPD concentration (second morning-void) measured by CLIA (y) and enzyme immunoassay (EIA) for adult volunteers (n = 449) with and without bone disease revealed a best fit equation of: y = 1.08 ± 0.03x - 1.15 ± 0.98 nmol/L (r = 0.964, S_yx = 14 nmol/L). CLIA and EIA methods were correlated with HPLC measurement of urinary free DPD (r = 0.846 and 0.871, respectively). For healthy adults, the creatinine-normalized excretion of DPD (mean ± SD) measured by CLIA for 61 men (4.1 ± 1.2 µmol DPD/mol creatinine) and 76 premenopausal women (5.3 ± 1.8 µmol DPD/mol creatinine) did not differ significantly (P >0.05) from DPD excretion measured by EIA, and both immunoassays showed a significant gender difference (P <0.001) in reference intervals. In a clinical trial, DPD excretion (µmol DPD/mol creatinine) measured by CLIA differed substantially from the reference population for 54 untreated pagetic (12.7 ± 8.0 SD), 255 untreated osteoporotic (7.5 ± 4.1), 21 osteomalacic (12.4 ± 8.5), 17 primary hyperparathyroid (9.4 ± 4.4), and 14 secondary hyperparathyroid (9.2 ± 5.1) patients. Clinical sensitivities of the CLIA and EIA methods range from 38% to 80% in bone disorders and limit the use of the DPD measurement in disease detection. DPD excretion after pamidronate treatment in a subgroup of the pagetic patients fell dramatically as assessed by CLIA or EIA. We conclude that the automated CLIA method for DPD is a convenient and reliable method that may aid in the evaluation and management of bone disease and is applicable to high volume testing in the routine clinical laboratory.

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