Clinical Validation of a New Immunoradiometric Assay for Intact Human Osteocalcin

Abstract

The purpose of this study was to estimate clinical validity of a new available immunoradiometric assay for circulating intact human BGP (N-tact Osteo SP) by measuring this protein in a large number of normal subjects and patients with the most common metabolic bone diseases. One hundred normal subjects were studied in order to obtain our normal ranges (4.9 +/- 1.7 ng/ml). The mean values found in 28 patients with primary hyperparathyroidism (17.5 +/- 22.8 ng/ml, P < 0.001), 15 glucocorticoid-treated patients (1.9 +/- 1.5, P < 0. 001), 10 patients with hypoparathyroidism (1.5 +/- 0.7, P < 0.001), 9 with hyperthyroidism (8.3 +/- 3.8, P < 0.001), 8 with skeletal metastases (7.2 +/- 2.3, P < 0.001), and 4 with humoral hypercalcemia of malignancy (2.42 +/- 1.91, P < 0.005) were significantly different from mean values found in normal subjects. Mean decrease of serum osteocalcin T-score values was significantly greater when evaluated by N-tact Osteo SP assay in 15 steroid-treated patients (-1.4 +/- 1.0) and 19 primary hyperparathyroid (PHPT) patients (3.6 +/- 1.9), compared with the mean values obtained with the Elsa-Osteo assay (-0.67 +/- 1.2, P < 0. 002 and 4.3 +/- 2.8, P < 0.04, respectively). We found significant correlations between the global skeletal uptake of 99mTc-methylendiphosphonate and serum BGP levels assayed by both N-tact Osteo SP (P < 0.01) and Elsa-Ost-Nat assay (P < 0.05). Our results indicate that this new immunoradiometric assay for the intact human osteocalcin has the potential for good discrimination between normal subjects and patients with both low and high bone turnover. Furthermore, our findings emphasize the fact that, in the absence of available standardized commercial assays, one should rely on only one assay because different results are obtained by different assays under different clinical conditions.

Normocalcaemic hypoparathyroidism: prevalence and effect on bone status in older women. The OPUS study

“…A few studies have shown that bone turnover marker levels are frankly low or low‐normal in patients with hypoparathyroidism compared to normal subjects, and these findings are consistent with histomorphometric analysis. In particular, double tetracycline labelling of bone biopsy specimens has demonstrated that dynamic skeletal indices are suppressed in hypoparathyroid patients .…”

“…Furthermore, despite significant changes in bone turnover, teriparatide did not provide any significant BMD improvement in hypoparathyroidism . In particular, after 3 years of twice daily PTH treatment, BMD and bone mineral content (BMC) at the lumbar spine, femoral neck and whole body remained stable although there was a nonsignificant downward trend in BMD at the distal radius.…”

Concentrations of Follicle-Stimulating Hormone Correlate with Alkaline Phosphatase and a Marker for Vitamin K Status in the Perimenopause

“…12 Moreover, lack of a standardized commercial assay complicates comparison of concentrations among studies. 13 Undercarboxylated osteocalcin (ucOC) is a precise indicator of vitamin K status. It reflects vitamin K's role in carboxylating glutamic acid residues on the protein that subsequently facilitates the binding of OC to hydroxyapatite in bone.…”

Lumbar bone mineral density as the major factor determining increased prevalence of vertebral fractures in monoclonal gammopathy of undetermined significance

“…Bone isoenzyme of alkaline phosphatase (BALP) was determined with an immunoenzymatic assay (Metra BAP EIA Kit, Quidel Corporation, San Diego, CA, USA) (Gomez et al, 1995); intraand inter-assay coefficients of variation were less than 5AE6 and 7AE8% respectively. Serum osteocalcin (BGP) was determined with an immunoradiometric assay (BGP; N-tact Osteo SP, DiaSorin, Stillwater, MN, USA) (Minisola et al, 1999); intraand inter-assay coefficients of variation were less than 4AE5 and 9AE5% respectively. Bone sialoprotein (BSP) was determined using a radioimmunoassay (Immunodiagnostik AG, Bensheim, Germany) described elsewhere (Karmatschek et al, 1997).…”