Time course of 25(OH)D3 vitamin D3 as well as PTH (parathyroid hormone) during fracture healing of patients with normal and low bone mineral density (BMD).

BACKGROUND: Until now the exact biochemical processes during healing of metaphyseal fractures of healthy and osteoporotic bone remain unclear. Especially the physiological time courses of 25(OH)D(3) (Vitamin D) as well as PTH (Parathyroid Hormone) the most important modulators of calcium and bone homeostasis are not yet examined sufficiently. The purpose of this study was to focus on the time course of these parameters during fracture healing. METHODS: In the presented study, we analyse the time course of 25(OH)D3 and PTH during fracture healing of low BMD level fractures versus normal BMD level fractures in a matched pair analysis. Between March 2007 and February 2009 30 patients older than 50 years of age who had suffered a metaphyseal fracture of the proximal humerus, the distal radius or the proximal femur were included in our study. Osteoporosis was verified by DEXA measuring. The time courses of 25(OH)D(3) and PTH were examined over an eight week period. Friedmann test, the Wilcoxon signed rank test and the Mann-Withney U test were used as post-hoc tests. A p-value ≤ 0.05 was considered significant. RESULTS: Serum levels of 25(OH)D(3) showed no differences in both groups. In the first phase of fracture healing PTH levels in the low BMD level group remained below those of the normal BMD group in absolute figures. Over all no significant differences between low BMD level bone and normal BMD level bone could be detected in our study. CONCLUSIONS: The time course of 25(OH)D(3) and PTH during fracture healing of patients with normal and low bone mineral density were examined for the first time in humans in this setting and allowing molecular biological insights into fracture healing in metaphyseal bones on a molecural level. There were no significant differences between patients with normal and low BMD levels. Hence further studies will be necessary to obtain more detailed insight into fracture healing in order to provide reliable decision criteria for therapy and the monitoring of fracture healing.

Anamnestic risk factor questionnaire as reliable diagnostic instrument for osteoporosis (reduced bone morphogenic density).

BACKGROUND: Osteoporosis is a major health problem worldwide, and is included in the WHO list of the top 10 major diseases. However, it is often undiagnosed until the first fracture occurs, due to inadequate patient education and lack of insurance coverage for screening tests. Anamnestic risk factors like positive family anamnesis or early menopause are assumed to correlate with reduced BMD. METHODS: In our study of 78 patients with metaphyseal long bone fractures, we searched for a correlation between anamnestic risk factors, bone specific laboratory values, and the bone morphogenic density (BMD). Each indicator was examined as a possible diagnostic instrument for osteoporosis. The secondary aim of this study was to demonstrate the high prevalence of osteoporosis in patients with metaphyseal fractures. RESULTS: 76.9% of our fracture patients had decreased bone density and 43.6% showed manifest osteoporosis in DXA (densitometry) measurements. Our questionnaire, identifying anamnestic risk factors, correlated highly significantly (p = 0.01) with reduced BMD, whereas seven bone-specific laboratory values (p = 0.046) correlated significantly. CONCLUSIONS: Anamnestic risk factors correlate with pathological BMD. The medical questionnaire used in this study would therefore function as a cost-effective primary diagnostic instrument for identification of osteoporosis patients.

Development and validation of an immunoluminometric assay (ILMA) for fetuin-A-glycoprotein.

BACKGROUND: To identify dialysis patients with low fetuin-A levels, a sensitive immunoluminometric assay (ILMA) was developed. METHODS: For the two-site ILMA, one monoclonal antibody was coated to polystyrene beads and one polyclonal antibody was labelled with acridinium ester. RESULTS: The lower detection threshold was 0.013 g/L, with the normal range 0.20-0.87 g/L (arithmetic mean 0.437 +/- 0.118 g/L). Serum fetuin-A levels in the dialysis patients were significantly lower (arithmetic mean: 0.352 +/- 0.099 g/L, p < 0.0001). CONCLUSION: This ILMA has been proved to be a reliable method for the determination of serum fetuin-A concentrations in dialysis patients.

26 years of external quality controls for the screening of congenital metabolic disorders in newborns--a summary of the results.

The evaluation of the inter-laboratory tests over the 26 year period shows a clear improvement in the analysis quality of the test participants. This can be clearly seen in the increased recovery rates of the pathological quality control samples. Centers are put in the position to adjust their own quality control measures for their analysis to international standards, thereby decreasing the error rate in their analyses. The introduction of the tandem mass spectrometer for newborn screening is inevitably connected to even higher requirements in the quality of the measured values. Up to now, though, commercially or scientifically determined external quality controls do not exist. In November 2005, as a start, we tentatively expanded our (since 1982) existing inter-laboratory controls to include parameters determinable by mass spectrometry. A second external control will take place in May 2008 for acylcarnitines.

Use of cinacalcet HCl to achieve the recommended targets of bone metabolism in a patient with therapy-resistant renal hyperparathyroidism.

We report on a patient with end-stage renal disease and severe progressive secondary hyperparathyroidism, whose condition failed to respond to conventional pharmacologic or surgical interventions. Although immunotherapy produced a partial response, it failed to decrease serum parathyroid hormone to the levels recommended by the National Kidney Foundation Kidney Disease Outcomes Quality Initiative clinical practice guidelines. Treatment with a new calcimimetic agent, cinacalcet HCl (Mimpara, Amgen, Munich, Germany), resulted in a rapid decline in elevated parathyroid hormone levels, near normalization of other laboratory markers of bone metabolism, improvement in mobility and skeletal pain caused by renal osteodystrophy, and an increase in body weight.

Calcium load during administration of calcium carbonate or sevelamer in individuals with normal renal function.

BACKGROUND: Under steady-state conditions urinary calcium (Ca) excretion corresponds to the Ca load in healthy subjects. However, in chronic haemodialysis patients reliable data on Ca load are not available. In these patients Ca-containing phosphate binders are suspected to play a role in the progression of arteriosclerosis via increased but not quantified Ca load. The present study evaluated the effect of calcium carbonate (CC) and sevelamer hydrochloride (SEV), a calcium-free phosphate binder, on serum Ca and urinary Ca excretion in healthy individuals. METHODS: Twelve healthy male individuals were included in a monocentre, randomized, single-blind, placebo-controlled, three-way crossover phase I study. Concurrently with their meals, participants received 4 x 2 tablets of SEV (800 mg), CC (500 mg) or placebo for 6 days with 1-week washout between the treatment periods. During the study, weekly blood samples were taken and 24-h urine was collected each day for measurement of calcium, magnesium, phosphorus, chloride and iPTH. RESULTS: Mean daily urinary phosphorus excretion was significantly lower in subjects undergoing SEV treatment compared to those taking placebo (P < 0.001). Mean daily total urinary excretion of calcium was significantly higher in CC-treated participants compared to those receiving placebo (P < 0.001). Mean 24-h calcium excretion during the 6 treatment days was 6.60 +/- 2.62 mmol [265 +/- 105 mg] (CC) versus 5.15 +/- 2.16 mmol [206 +/- 87 mg] (SEV) versus 4.95 +/- 1.63 mmol [198 +/- 65 mg] (Placebo). Taking into account nutritional calcium intake estimated from dietary records fractional calcium absorption was 8.7% (CC), 13.3% (placebo) and 14.8% (sevelamer). CONCLUSION: Intake of calcium carbonate compared to placebo in contrast to sevelamer in healthy individuals was associated with increased total urinary calcium excretion indicating an increased calcium load due to increased intestinal calcium absorption.

Accuracy and clinical implications of seven 25-hydroxyvitamin D methods compared with liquid chromatography-tandem mass spectrometry as a reference.

BACKGROUND: The most reliable assessment of vitamin D status is measurement of plasma 25-hydroxyvitamin D (25[OH]D) concentration. High variability in 25(OH)D measurements due to utilized test and assay technologies and the lack of standardization against reference materials and reference method often confounds proper assessment of vitamin D status. METHODS: We evaluated the accuracy of six routinely available methodologies: high-performance liquid chromatography (HPLC), the IDS-radioimmunoassay (IDS-RIA) and enzyme immunoassay (IDS-EIA), the Nichols Advantage automated protein-binding assay (Advantage), two versions of the DiaSorin automated immunoassay (Liaison 1 and Liaison 2)--and one prototype automated immunoassay (Elecsys) for assessment of the 25(OH)D(3) status in a cohort of 300 randomly selected patients' samples compared with the reference method liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: Passing-Bablok regression analysis demonstrated a slope for each method compared with LC-MS/MS that varied from 0.62 (IDS-EIA) to 1.0 (HPLC). The Advantage and the Liaison 1 showed significant deviation from linearity with highly variable individual results vs. the LC-MS/MS. Difference plots revealed a considerable persistent proportional bias for the IDS-RIA and IDS-EIA. All evaluated methods except HPLC demonstrated a more or less considerable deviation of individual 25(OH)D(3) values compared with LC-MS/MS defined target concentrations. CONCLUSIONS: Standardization of methods for the quantification of 25(OH)D on a human-based sample panel by means of LCMS/MS would help to reduce the inter-method variability with respect to accuracy existing in 25(OH)D measurement considerably. However, there will still remain differences in the accuracy of methods utilizing sample purification before final quantification or immunological reaction when compared with those methods without separate sample purification.

The effect of B-vitamins on biochemical bone turnover markers and bone mineral density in osteoporotic patients: a 1-year double blind placebo controlled trial.

BACKGROUND: Hyperhomocysteinemia is a new risk factor for osteoporosis. This study analyzed the effect of a homocysteine (HCY)-lowering treatment in osteoporotic individuals. METHODS: Osteoporotic subjects (n=47, 55-82 years) were treated with either a combination of 2.5 mg folate, 0.5 mg vitamin B(12) and 25 mg vitamin B(6) or placebo. Bone mineral density (BMD) at lumbar spine and hip was measured at baseline and after 1 year. Urinary desoxypyridinoline cross-links (DPD) and plasma levels of tartrate resistant acid phosphatase (TRAP), C-terminal cross-links of collagen I (CTx), pro-collagen type I N-terminal peptide (PINP) and osteocalcin (OC) were measured after 0, 4, 8 and 12 months. RESULTS: B-vitamin supplementation significantly reduced HCY (0 vs. 12 months: 13.6+/-4.8 vs. 8.9+/-2.4 micromol/L). Placebo treatment had no effect on HCY (0 vs. 12 months: 12.0+/-3.4 vs. 12.7+/-3.9 micromol/L). BMD, TRAP, CTx, OC and PINP did not change throughout the study in both groups. Vitamin treatment decreased urinary DPD by -13% (p<0.01) after 8 and 12 months. In a sub-group analysis of hyperhomocysteinemic subjects (HCY>15 mumol/L, n=8), B-vitamin treatment tended to increase BMD at the lumbar spine, with a t-score from -2.7 to -1.7, and to decrease OC and PINP by approximately 50%. CONCLUSIONS: B-vitamin supplementation had no consistent effects on bone turnover or BMD. However, the situation may be different in patients with hyperhomocysteinemia.

Influence of the sample matrix on the stability of beta-CTX at room temperature for 24 and 48 hours.

The measurement of beta-C-telopeptides of type I collagen (beta-CTX) reflects the rate of bone resorption in a variety of metabolic bone disorders and it is increasingly used to assist diagnosis and follow-up of these pathologies. Since preanalytical biases in the results of this marker can decrease its clinical usefulness, specific stability studies should be developed to prevent that inconsistent results of laboratory testing might affect patient health and waste economical resources. Three blood samples were simultaneously collected without venous stasis into evacuated tubes containing no additives, K2 EDTA or lithium heparin, from 23 out-patients referred to our phlebotomy service for routine laboratory testing. After centrifugation and separation of the specimens, a first aliquot was immediately analyzed, whereas a second and third aliquot was processed after a 24- and 48-hour storage at room temperature (21 degrees C). Beta-CTX was assayed on the automated electrochemiluminescence analyzer E170. A modest and clinically irrelevant underestimation was observed in lithium heparin plasma when compared with either K2 EDTA (-7.1%; 95% C.I. -2.0 to -12.3%; p < 0.001) or serum (-7.8%; 95% C.I. -3.2 to -12.4%; p < 0.001), but not between serum and K2 EDTA (+0.8%, 95% C.I. -5.3 to +6.9%; p = 0.260). Storage at room temperature in K2 EDTA plasma introduced a modest and clinically negligible decay in immunoreactivity (-4.4% and -5.7% at 24 and 48 hours, respectively), whereas storage at room temperature in both serum (-17.6% and -28.6% at 24 and 48 hours, respectively) and lithium heparin plasma (-29.1% and -44.0% at 24 and 48 hours, respectively) was associated with a substantial decay and a larger inter-individual variability in the measurable concentration of the analyte. In conclusion, the results of our investigation demonstrate that EDTA plasma is the most suitable sample matrix for the storage of beta-CTX at room temperature after centrifugation.

Insufficient vitamin D supply as a possible co-factor in colorectal carcinogenesis.

Vitamin D, the "sunshine vitamin", may play a role in the development of colorectal cancer. In a prospective open study, the plasma levels of 25-hydroxyvitamin D [25(OH)D], the marker for sufficient or insufficient vitamin D supply, were determined in three groups of patients whose diagnoses were confirmed by colonoscopy: healthy individuals (n = 239), patients with colorectal adenoma (n = 203) and with carcinoma (n = 98). In order to assess other factors such as nutrition, sunlight exposure and physical activity as co-variates for the risk of colorectal cancer, the individuals completed a questionnaire. Patients with colorectal cancer (CRC) had significantly decreased plasma 25(OH)D levels (p < 0.001) compared to the controls in contrast to patients with adenomas, who had lower levels exclusively in the winter (p = 0.01). When analyzed by the Kruskal-Wallis test, the groups of patients with adenomas (p = 0.03) and colorectal carcinomas (p < 0.0001) had significantly different mean plasma values compared to the controls. The plasma 25(OH)D levels showed an inverse correlation to the UICC stages of CRC; however, the differences were not significant. Patients with CRC were significantly older than the controls, but regression analysis showed no significant correlation between the plasma 25(OH)D levels and age, and the influence of age on the plasma levels of 25(OH)D was minimized in a group of individuals over 65 years of age, in which the patients with CRC had significantly decreased plasma levels of 25(OH)D in the winter. About one-half of the individuals with normal colonic mucosa had plasma 25(OH)D levels below 25 microg/l (the normal range) and one-third even had plasma levels below 20 microg/l. Regression analysis showed a significant influence of age on plasma 25(OH)D levels in healthy individuals, of physical activity in patients with adenomas and of season in patients with CRC. Other covariates, such as nutrition or sunlight exposure, had no significant influence on plasma 25(OH)D. In conclusion, an insufficient vitamin D supply might act as a co-factor in colorectal carcinogenesis.

Serum TRACP 5b is a useful marker for monitoring alendronate treatment: comparison with other markers of bone turnover.

UNLABELLED: We studied clinical performance of serum TRACP 5b and other bone turnover markers, including S-CTX, U-DPD, S-PINP, S-BALP, and S-OC, for monitoring alendronate treatment. TRACP 5b had higher clinical sensitivity, area under the ROC curve, and signal-to-noise ratio than the other markers. INTRODUCTION: The purpose of this study was to compare the clinical performance of serum TRACP 5b (S-TRACP5b) with that of other markers of bone turnover in the monitoring of alendronate treatment. MATERIALS AND METHODS: This double-blinded study included 148 healthy postmenopausal women that were randomly assigned into two groups: one receiving 5 mg alendronate daily (n=75) and the other receiving placebo (n=73) for 12 months. All individuals in both groups received calcium and vitamin D daily. The bone resorption markers S-TRACP5b, serum C-terminal cross-linked telopeptides of type I collagen (S-CTX), and total urinary deoxypyridinoline (U-DPD), and the serum markers of bone formation procollagen I N-terminal propeptide (S-PINP), bone-specific alkaline phosphatase (S-BALP), and total osteocalcin (S-OC) were assessed at baseline and at 3, 6, and 12 months after initiation of treatment. Lumbar spine BMD (LBMD) was measured at baseline and 12 months. RESULTS: Compared with the placebo group, LBMD increased, and all bone markers decreased significantly more in the alendronate group (p<0.001 for each parameter). The decrease of S-TRACP5b after first 3 months of alendronate treatment correlated significantly with the changes of all other markers except S-OC, the best correlation being with S-CTX (r=0.60, p<0.0001). The changes of LBMD at 12 months only correlated significantly with the changes of S-TRACP5b (r=-0.32, p=0.005) and S-CTX (r=-0.24, p=0.037) at 3 months. Based on clinical sensitivity, receiver operating characteristic (ROC) curves, and signal-to-noise ratio, S-TRACP5b, S-CTX, and S-PINP were the best markers for monitoring alendronate treatment. Clinical sensitivity, area under the ROC curve, and signal-to-noise ratio were higher for S-TRACP5b than for the other markers. CONCLUSION: These results show that S-TRACP5b, S-CTX, and S-PINP are useful markers for monitoring alendronate treatment.

Fecal leukocyte proteins in inflammatory bowel disease and irritable bowel syndrome.

UNLABELLED: The aim of this prospective study was to compare five different leukocyte proteins in feces of patients with chronic inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and healthy persons who underwent prophylactic colonoscopy. METHODS: The leukocyte proteins calprotectin, lactoferrin, lysozyme, myeloperoxidase, and PMN-elastase were determined with immunoassays in fecal samples of three consecutive feces (e.g. three days) in 40 healthy persons, 39 patients with chronic IBD (of these 21 with Crohn's disease and 18 with ulcerative colitis), and 40 patients with IBS. RESULTS: ROC curves calculated for healthy persons and patients with IBD yielded the following areas under the curves (AUCs): PMN-elastase 0.916, calprotectin 0.872, myeloperoxidase 0.750, lysozyme 0.726, and lactoferrin 0.693. The AUCs of PMN-elastase and calprotectin were not significantly different (p = 0.327), whereas PMN-elastase or calprotectin vs. the other proteins were significantly different (p < 0.001). PMN-elastase and calprotectin correlated with the endoscopically classified severity of inflammation. All fecal leukocyte markers in IBS were found in the range of the healthy persons. Data on storage stability of leukocyte proteins in fecal supernatants are given. CONCLUSION: Fecal PMN-elastase and calprotectin support the differentiation of chronic IBD from IBS and correlate with the severity of inflammation.

Comparison of different salivary and fecal antibodies for the diagnosis of celiac disease.

To investigate the detectability and expressiveness of salivary and fecal anti-gliadin (AGA), anti-endomysium (EMA) and anti-tissue-transglutaminase (ATA) antibodies, 127 salivary and 160 fecal samples of healthy volunteers and salivary and fecal samples of 17 patients with histologically proven and 9 patients with suggested celiac disease were investigated in this study. With all salivary parameters and fecal IgA AGA, IgM AGA, IgA EMA and IgG EMA, healthy volunteers and patients showed partially overlapping results. The most promising results in our study with higher concentrations in patients with celiac disease were obtained by fecal scIgA AGA and a combined determination of fecal IgA AGA, IgG AGA and IgM AGA. Further investigations should be performed with fecal IgA EMA and scIgA ATA based on human recombinant tissue-transglutaminase. One patient with histologically proven celiac disease had normal serological but high fecal scIgA AGA and scIgA ATA values. This patient emphasizes the importance of fecal antibody determination for the diagnosis of celiac disease, at least in patients with suggested celiac disease and negative serum antibodies.

Establishment of reference intervals for enzyme catalytic activity concentration measurements at 37 degrees C--a practical approach.

The change from measuring enzyme catalytic activity concentrations from 25 degrees C to 37 degrees C in the German Federal Republic has led to the need for new reference ranges for defined patient groups and for healthy individuals. Up to now, these are only present as tentative values and are incomplete, especially for children. This article describes a method for deriving reference ranges from results obtained from measurement at 25 degrees C and 37 degrees C and the use of percentiles to establish values for 37 degrees C. A total of 1,111,378 data from 507,305 patients were used to establish reference ranges for the following 11 enzymes at 37 degrees C using the test kits from Roche Diagnostics measured on the Modular analyser: acid phosphatase, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, cholinesterase, creatine kinase, creatine kinase - MB subunit, gamma glutamyl transpeptidase, glutamate dehydrogenase, lactate dehydrogenase and lactate dehydrogenase - isoenzyme 1. The computed reference ranges from the data used gave rise to reference ranges, some of which were in agreement with the data from the producer, some of which, however, showed deviations from the values given by the producer. Ranges for newborns, children and adolescents could be computed with the prerequisite that ranges for 25 degrees C were available and that these had been established and validated. This method of establishing reference ranges for catalytic enzyme activities can be used for all producers, providing the number of data used is sufficient to allow for valid statistical analysis.

Performance evaluation of automated assays for beta-CrossLaps, N-MID-Osteocalcin and intact parathyroid hormone (BIOROSE Multicenter Study).

INTRODUCTION: Biochemical markers of bone metabolism have been mainly determined manually until now and the precision and accuracy of these methods have not always been satisfactory. This has been shown in several external quality assessment schemes (EQAS). OBJECTIVE AND STUDY DESIGN: A study named BIOROSE was undertaken to evaluate new automated assays for serum markers of bone metabolism. The main focus was to evaluate the assay performance in a multicenter setting with 20 laboratories participating in Germany. The evaluation consists of a familiarization phase to determine precision and accuracy and an EQAS to evaluate the comparability between laboratories. MATERIALS: The parameters beta-CrossLaps (CTX), N-MID-Osteocalcin (OC) and intact parathyroid hormone (PTH) were measured with reagents including calibrators and control sera obtained from Roche Diagnostics, Mannheim, Germany, with electrochemiluminescence immunoassays (ECLIA) on the automated analyzer Elecsys 2010. RESULTS: We calculated for the control samples, PCB 1-3, the mean and median values from the measured values of all participating laboratories and used these as target values. From these target values, a recovery range for the participating laboratories was calculated for beta-CrossLaps, OC and intact PTH of better than 80-126% for PCB 2 and PCB 3, and for PCB 1 (low concentration range) for beta-CrossLaps 79-129%, OC 90-120% and intact PTH 78-126%. The between-day imprecision was 2.4-7.2% for beta-CrossLaps, 1.1-5.9% for OC and 1.7-5.5% for intact PTH in the elevated range (sample PCB 2). In the EQAS, the inter-laboratory imprecision for beta-CrossLaps in the sample with a value of 0.8 ng/ml (above the upper limit of normal, which is 0.6 ng/ml) was 9.8% on day 1 and 9.7% on day 2. CONCLUSION: The performance evaluation of automated assays for beta-CrossLaps, N-MID-Osteocalcin and intact parathyroid hormone in the BIOROSE multicenter study showed that the participating laboratories had no problems in setting up these methods and they yielded results for precision and accuracy that are superior to results achieved in external quality assessment schemes for manually performed methods. In addition, at the clinically important decision level of the upper limit of the normal range, all three tested analytes gave precise results that improved medical decisions.

Evaluation of serum beta-carboxy-terminal cross-linking telopeptide of type I collagen as marker of bone resorption in chronic hemodialysis patients.

BACKGROUND: The carboxy-terminal cross-linking telopeptide of type I collagen (beta-CrossLaps, beta-CTX) is released into the circulation during degradation of type I collagen and serves as a marker of bone resorption. beta-CTX is known to undergo a diurnal rhythm in normal individuals and to accumulate in chronic renal failure. beta-CTX has a potential role in noninvasive diagnosis of renal bone disease. METHODS: Serum beta-CTX was compared to parathyroid hormone (PTH) and other biochemical bone markers in 90 unselected hemodialysis patients. RESULTS: Mean beta-CTX was elevated above the normal range (1.72 +/- 0.93 microg/l); there were large individual variations. Serum beta-CTX was significantly correlated with various PTH assays (r >0.56) and with tartrate-resistant acid phosphatase 5b (TRACP 5b, r = 0.629), bone-specific alkaline phosphatase (r = 0.404) and osteocalcin (r = 0.534, all correlations p < 0.001). The correlation between beta-CTX and PTH was significantly higher than the correlation between TRACP 5b and PTH. Several factors which could confound interpretation of serum beta-CTX were assessed in further studies: (i) There was no recognizable influence of the time of blood sampling (morning dialysis shift versus afternoon dialysis shift) on serum beta-CTX. (ii) Serum beta-CTX was not significantly related to residual diuresis of patients. CONCLUSIONS: We found a high association between beta-CTX and other established markers of bone and calcium metabolism demonstrating the potential utility of beta-CTX as marker of bone resorption in renal bone disease. However, further studies employing bone histology are still warranted to exactly define the influence of glomerular retention on serum beta-CTX in end-stage renal disease.

Influence of PTH assay methodology on differential diagnosis of renal bone disease.

BACKGROUND: Determination of plasma parathyroid hormone (PTH) is routinely performed to diagnose and monitor renal bone disease. Recently, a new PTH assay ('whole PTH') using an antibody directed specifically against PTH(1-4) has been introduced. It was the aim of the current study to evaluate whole PTH and parameters derived from whole PTH in renal bone disease. METHODS: The following measurements were carried out in blood samples from 141 unselected haemodialysis patients: three intact PTH assays (Nichols, Roche Elecsys), Scantibodies total); whole PTH (Scantibodies); bone-specific alkaline phosphatase (bAP); tartrate-resistant acid-phosphatase 5b (TRAP 5b); osteocalcin, 25-hydroxyvitamin D. Parameters derived from whole PTH were: (i) non-PTH(1-84), difference between intact PTH (Scantibodies assay) and whole PTH; (ii) whole PTH/non-PTH(1-84) ratio. RESULTS: The values generated by the intact PTH assays were comparable. The mean whole PTH concentration was lower than mean intact PTH concentrations (16.9+/-18.1 vs 26.4+/-30.5 pmol/l, Nichols, P<0.05). The correlation coefficients between all four PTH assays were comparable and were very high (r>0.96, ns). The rank order of values generated by the whole PTH assay was statistically not significantly different from the rank order generated by the Nichols intact PTH assay. The median non-PTH(1-84) concentration was 5.2 pmol/l (range 0-49.4). All PTH assays correlated highly significantly with non-PTH(1-84) (correlation coefficients 0.83-0.92). Corrected serum calcium was also associated with non-PTH(1-84) but the correlation was weaker (r=0.28). Regression analysis indicated that the non-PTH(1-84) concentration could be predicted by 76.6-84.6% by the prevailing intact PTH concentrations. Other parameters contributed only marginally to prediction of non-PTH(1-84). In the entire patient group, there was no statistically significant correlation between the whole PTH/non-PTH(1-84) ratio and any of the PTH assays or biochemical bone markers. Eight of 141 patients had a whole PTH/non-PTH(1-84) ratio <1. TRAP 5b, bAP and osteocalcin had high correlations with intact PTH assays and the whole PTH assay (correlation coefficients 0.51-0.56, no significant difference). None of the PTH assays was superior to any other PTH assay in predicting serum concentrations of the bone markers. Therapy with active vitamin D metabolites (n=70) did not alter the results of our analyses. CONCLUSIONS: With respect to information about bone turnover we were not able to find differences between whole PTH and intact PTH assays. Our data also suggest that whole PTH and intact PTH assays give similar information. (i) The correlation between all PTH assays was very high. (ii) The rank order between whole PTH and Nichols intact PTH assays was comparable. (iii) The association between intact PTH assays and non-PTH(1-84) was very high. Albeit non-PTH(1-84) was mostly determined by the prevailing intact PTH concentration, diagnostic information on parathyroid activity provided by whole PTH or intact PTH, respectively, may differ in individual patients. How often this would happen cannot be answered with the currently available data. Unequivocal structural identification of the non-PTH(1-84) fraction would facilitate the answer to that question. The use of the whole PTH/non-PTH(1-84) ratio as a biochemical bone marker in renal bone disease requires further investigation.

Markers of bone resorption--measurement in serum, plasma or urine?

OBJECTIVE: We compared an established urine marker (total deoxypyridinoline (DPD), related to creatinine (cr)) with a plasma marker (CTX) to evaluate whether the methods are equally suited to detect increased bone resorption in women after the menopause and to see whether both markers show normal bone resorption in postmenopausal women on hormone replacement therapy (HRT). METHODS: DPD in first morning void urines was measured by an automated HPLC system. CTX ("beta-CrossLaps") was measured on the automated electrochemiluminescence analyzer E170 (Roche Diagnostics, Germany). For CTX, EDTA plasma and serum samples taken from fasting patients in the morning between 08.00 and 08.30 were analyzed. 49 women were premenopausal, 43 women were postmenopausal without HRT, and 13 women were postmenopausal on HRT (mostly on oral medication) for more than six months. RESULTS AND DISCUSSION: Inter-assay coefficients of variation (CVs) at three different concentrations were 6.0%, 6.7% and 7.2% for the assay of DPD and 2.58%, 1.83% and 1.99% for CTX, respectively. CTX was more stable in EDTA plasma than in serum. 21/43 (49%) of postmenopausal women without HRT showed increased DPD/cr ratios and 19/43 (44%) showed elevated CTX concentrations. Regarding postmenopausal women on HRT, DPD/cr ratios were elevated in 3/13 women, whereas plasma CTX showed levels within the premenopausal range in all 13 women. It is discussed that in some cases a lower muscle mass as a result of increasing age or as a result of oral HRT might increase the urinary DPD/cr ratio by lowered excretion of cr. This effect would raise the number of cases with an elevated DPD/cr ratio after the menopause out of proportion. CONCLUSION: CTX is determined with very high precision on the E170. CTX, if measured in EDTA plasma samples from fasting patients in the morning, seems to indicate bone resorption in women on HRT correctly as normal. The DPD/cr ratio in urine of women on HRT is increased in some cases above normal, presumably by lowered excretion of cr. According to our results, plasma (or serum) markers of bone resorption seem to be preferable over cr-related urine markers.