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Background: Myeloma-induced bone loss is related to an uncoupling of bone formation and bone resorption. The aim of the present study was to assess the potential clinical value of biochemical markers of bone formation in the work up of patients with plasma cell dyscrasias., Methods: Serum total alkaline phosphatase, bone-specific alkaline phosphatase (BAP), and osteocalcin (OC) were measured in 43 patients with newly diagnosed multiple myeloma (MM), in 40 patients with monoclonal gammopathy of undetermined significance (MGUS), in 40 patients with untreated benign vertebral osteoporosis (OPO), and in 48 healthy adults., Results: In MM and MGUS patients, serum BAP, but not serum OC, was lower than in healthy controls (P<0.05). Serum OC was higher in patients with OPO than in healthy controls (P<0.05). The strongest associations between markers were found in OPO patients and in healthy adults. MM patients with early-stage disease or without detectable osteolysis had decreased serum BAP values (P<0.05). Serum OC was higher in MM patients with stage III disease (P<0.05) than in healthy controls. MM patients with OPO-like bone involvement had lower BAP values than sex- and age-matched MGUS patients with OPO-like bone involvement and patients with benign OPO (P<0.05)., Conclusions: In patients with plasma cell dyscrasias, serum BAP, rather than serum OC, appears to reflect a suppressed bone formation rate and may be helpful in the differentiation between benign and myeloma-induced OPO. However, the overall clinical use of biochemical markers of bone formation in patients with plasma cell dyscrasia appears limited.

Biochemical markers of bone turnover have been shown to provide valuable information for the diagnosis and monitoring of metabolic bone disease. However, these dynamic indexes are influenced by a number of factors that need to be clearly identified to improve their clinical usefulness. To evaluate the contributions of anthropometric, life style, and environmental variables on bone turnover, biochemical markers of bone metabolism were determined in a population-based sample of 580 adults, aged 50-81 yr (297 men and 283 women). Subjects were recruited during 14 consecutive months within the framework of the European Vertebral Osteoporosis Study. Serum total and bone-specific alkaline phosphatase (S-BAP), serum C-terminal propeptide of type I collagen, and serum osteocalcin (S-OC) were measured as bone formation markers. Urinary total pyridinoline and deoxypyridinoline were included as bone resorption indexes. In females, serum levels of 25-hydroxyvitamin D3 were significantly higher (P < 0.01) in summer (May-September) than in winter (October-April), whereas no significant differences were found in males. In both sexes, no seasonal changes were seen in serum PTH. In males, serum total alkaline phosphatase (P < 0.01), S-BAP (P < 0.001), and S-OC (P < 0.05) were significantly higher in winter than in summer. During the same period, females had higher values of S-BAP (P < 0.05), S-OC (P < 0.01), and urinary pyridinoline and deoxypyridinoline (P < 0.001, respectively). Univariate analyses of the effects of life style habits on markers of bone metabolism revealed that in females, regular alcohol consumption and current smoking led to a suppression of markers of bone turnover, whereas in males, only alcohol intake was associated with such changes. In contrast, physical activity was associated with higher levels of bone formation markers and reduced levels of bone resorption indexes in both sexes. As shown by multivariate regression analyses, seasonal variations accounted for more of the variability in most biomarkers (up to 12%) than any of the other anthropometric or life style factors except age. This effect may be attributed to subclinical vitamin D deficiency during the winter period, which is common in countries of the northern hemisphere. We conclude that seasonal variation contributes significantly to the biological variability of bone turnover and needs consideration when interpreting the results of bone marker measurements.

To evaluate the diagnostic validity of new assays for bone-specific alkaline phosphatase (BAP), we compared measurements of total alkaline phosphatase (TAP) in serum with results for three different assays of serum BAP in healthy adults (n = 119), patients with chronic nonskeletal disorders (n = 123), and patients with metabolic bone diseases (n = 113). Serum TAP was determined by a standard colorimetric assay, BAP by the methods of lectin precipitation (L-BAP), enzyme immunoassay (E-BAP), and immunoradiometric assay (I-BAP). Impairment of liver function resulted in significant increases of all alkaline phosphatase (AP) measurements, with the smallest changes being exhibited by E-BAP. Compared with the results by TAP, diagnostic sensitivity (i.e., of values exceeding the reference interval) was not improved by BAP, but receiver-operating characteristic (ROC) curve analyses revealed improved discrimination for primary hyperparathyroidism by E-BAP. These results indicate that, in the presence of liver disease, the specificity of AP measurements is improved by measuring BAP. In most other clinical situations, serum TAP appears to provide sufficient clinical information; however, the cross-sectional study design used here allows no statement about the usefulness of BAP in serial measurements.

Bone metastases strongly affect skeletal metabolism by both their growth and their paracrine activities. However, so far no specific laboratory marker has been found to signal the spread of neoplastic disease to bone. We performed a cross-sectional study of 153 cancer patients and an equal number of healthy controls matched for sex and age, in which we determined serum levels of calcium and total alkaline phosphatase (TAP) as well as the fasting urinary excretion of calcium (uCa) and of the collagen cross-links pyridinoline (uPYD) and deoxypyridinoline (uDPD). The aim of the study was to analyze the diagnostic validity of the biochemical parameters measured with regard to neoplastic bone involvement. In the cancer group, 98 patients had overt bone metastases, as judged from radiographic and radioisotopic bone imaging. The remaining 55 patients were also in an advanced stage of disease, but there was no evidence of malignant bone involvement. In comparison to healthy controls, patients both with and without metastatic bone disease had significantly higher levels of TAP, uPYD, and uDPD (P < 0.0001). Only in cancer patients with bone metastases was the median serum calcium level higher than in the healthy controls (P < 0.02). uCa was the same in cancer patients and the control group. Within the collective of cancer patients, individuals with skeletal metastases had higher levels of serum calcium (P < 0.05), TAP (P < 0.01), and uPYD and uDPD (both P < 0.0001), than patients without evidence of malignant bone disease. uCa did not differ between the 2 groups of cancer patients. The cancer patients were then stratified into 4 subgroups according to the serum calcium level (< or = 2.6 mmol/L >) and the absence or evidence of bone metastases. This stratification revealed that in patients with bone metastases, uPYD and uDPD levels were similar in normocalcemic and hypercalcemic subjects, whereas in hypercalcemic patients, uCa levels significantly exceeded those in normocalcemic patients. When the efficacy of TAP, uCa, uPYD, and uDPD in discriminating between patients with and without bone metastases was evaluated by use of receiver-operating characteristic curves and stepwise multivariate regression analysis, uPYD was found to have the highest diagnostic validity. Using 50 mumol PYD/mol creatinine (i.e. the upper limit of normal range) as the cut-off level, the sensitivity of uPYD was 88.7%, whereas the specificity was only 41.8% (odds ratio, 5.598; 95% confidence interval, 2.547-12.306).(ABSTRACT TRUNCATED AT 400 WORDS)