Assessment of calciprotein particle formation by AUC of the absorbance change: effect of FYB-931, a novel bisphosphonate compound.

OBJECTIVE: Ectopic calcification such as vascular calcification, involves the formation of calciprotein particle (CPP), that is, colloidal particle of calcium phosphate bound to serum protein. In this study, a novel parameter for CPP formation was introduced, thereby the effect of FYB-931, a bisphosphonate compound was evaluated. METHODS: CPP formation in rat serum was assessed by the area under the curve (AUC) of the change in absorbance over time, and the commonly used T50, as indices. In vivo, the rats were treated with vitamin D3 to induce vascular calcification and then intravenously administered FYB-931 or etidronate thrice weekly for 2 weeks. KEY FINDINGS: In vitro, FYB-931 was the most potent inhibitor of CPP formation and it also inhibited the maximum response of CPP formation at higher concentrations. The AUC of the change in absorbance provided obvious dose-dependency, while T50 did not. FYB-931 dose-dependently prevented aortic calcification in vivo as well as CPP formation ex vivo more potently than etidronate. AUC showed a stronger correlation with the degree of aortic calcification than T50. CONCLUSIONS: The AUC in CPP formation can be an alternative parameter that reflects calcification. Based on the findings, FYB-931 has potential as an anti-calcifying agent.

Rapid calcification propensity testing in blood using a temperature controlled microfluidic polymer chip.

Phosphate toxicity is a major threat to cardiovascular health in chronic kidney disease. It is associated with oxidative stress, inflammation and the accumulation of calcium phosphate commonly known as calcification in soft tissues leading to functional disorders of blood vessels. An improved calcification propensity test for the assessment of phosphate toxicity was developed, which measures the velocity of calcium phosphate mineralization from colloidal precursors in vitro. This so called T50 test measures the transformation from a primary into a secondary form of nanosized colloidal plasma protein-calcium phosphate particles known as calciprotein particles. The T50 test in its previous form required a temperature controlled nephelometer and several hours of continuous measurement, which precluded rapid bed side testing. We miniaturized the test using microfluidic polymer chips produced by ultrasonic hot embossing. A cartridge holder contained a laser diode for illumination, light dependent resistor for detection and a Peltier element for thermo control. Increasing the assay temperature from 37°C to 75°C reduced the T50 test time 36-fold from 381 ± 10 min at 37°C to 10.5 ± 0.3 min at 75°C. Incorporating sputtered micro mirrors into the chip design increased the effective light path length, and improved signal-to-noise ratio 9-fold. The speed and reproducibility of the T50 chip-based assay run at 75°C suggest that it may be suitable for rapid measurements, preferably in-line in a dialyser or in a portable microfluidic analytic device with the chip inserted as a disposable cartridge.

Basic Calcium Phosphate Crystal Periarthritis Involving the Distal Interphalangeal Joints in a Patient with Systemic Lupus Erythematosus.

BACKGROUND Increased serum levels of basic calcium phosphate (BCP) and calcium pyrophosphate (CPP) are found in patients on dialysis, following trauma, and are associated with connective tissue diseases (CTDs), including dermatomyositis, scleroderma, and systemic lupus erythematosus (SLE). The shoulder is the joint most commonly associated with BCP crystal periarthritis. A report is presented of a case of BCP crystal periarthritis involving the distal interphalangeal (DIP) joints in a patient with SLE. CASE REPORT A 34-year-old woman with SLE presented with destructive arthritis of the DIP joints that developed during a two-year period, despite immunosuppressive therapy. Aspiration of synovial fluid from a DIP joint showed a lack of inflammatory cells, but the fluid was positive for the presence of crystals on alizarin red S histochemical staining. CONCLUSIONS A case of BCP crystal periarthritis is reported in a patient with SLE with chronic joint symptoms that were unresponsive to immunosuppressive therapy. This case has shown that chronic joint symptoms that are unresponsive to immunosuppressive therapy may be due to causes other than connective tissue disease (CTD) and that imaging studies and diagnostic workup that includes synovial fluid examination may support the diagnosis of BCP crystal periarthritis.

Ex vivo detection of calcium phosphate and calcium carbonate in rat blood serum.

The total calcium (tCa) in blood serum comprises free Ca2+ ions (fCa), protein-bound calcium (prCa), and complexed calcium by small anions (cCa). The cCa fraction, in addition to fCa, has been indicated to have some physiological activity. However, there is little evidence for the structure of its constituents. Here we report an ex vivo detection of the cCa constituents by synchrotron X-ray absorption near-edge structure spectroscopy. We collected the data directly on rat blood serum and, by making use of the reference samples, derived a spectrum that exhibits the features of cCa constituents. Among the features are those of the complexes of calcium phosphate and calcium carbonate. The detected complexes in the cCa fraction are mainly Ca(η2-HPO4)(H2O)4 and Ca(η1-HCO3)(H2O)5+, in which HPO42- and HCO3- serve as bidentate and unidentate ligands, respectively. The remained H2O molecules on the coordination sphere of Ca2+ enable these complexes to behave partially like aquated Ca2+ ions in protein-binding. Besides, as the dominant part of prCa, albumin-bound calcium (albCa) exhibits a spectrum that closely resembles that of fCa, indicating weak interactions between the protein carboxyl groups and calcium. The weak-bound cCa and albCa, along with fCa and the relevant anions, compose a local chemical system that could play a role in maintaining the calcium level in blood.

Calcium phosphate product level as a predictor for arteriovenous fistula re-operations in patients with chronic renal failure.

OBJECTIVES: There is an increased calcium phosphate product level causing the formation of calcification in the arterial wall and thus decreased quality of fistula in patients with chronic renal failure. The purpose of our study is to verify the relationship between arteriovenous fistula re-operation and high calcium phosphate product level. METHODS: Seventy-nine consecutive patients with chronic renal failure between April 2016 and February 2018 were included in the study. Patients having calcium phosphate product level ≥50 mg2/dl2 were defined as group 1, whereas those having <50 mg2/dl2 were defined as group 2. Primary outcome of interest was the need for re-operation during the follow-up and to determine the risk factors for re-operation. To determine independent predictors for re-operation, multivariate logistic regression model was used. RESULTS: The rates of redo and tredo operation were significantly higher in group 1 compared to group 2 ( p = 0.01 and 0.04). In multivariate analysis, phosphate (OR: 1.84, 95% CI: 1.00-3.40, p = 0.05) and triglyceride (OR: 1.01, 95% CI: 1.00-1.02, p = 0.04) levels for redo operation and calcium phosphate product level (OR: 1.11, 95% CI: 1.01-1.22, p = 0.03) for tredo operation were found to be independent predictors. CONCLUSIONS: High calcium phosphate product level leads to increased risk of arteriovenous fistula re-operation by causing arterial stiffness in this patient group. Additionally, these re-operations place additional burden on morbidity and cost efficacy. Thus, we recommend keeping the calcium phosphate product level at the optimal level in these patients to avoid both the risk of arteriovenous fistula re-operation and the other cardiovascular problems.

Associations between serum mineral metabolism parameters and mortality in patients on peritoneal dialysis.

AIM: Disturbances in mineral metabolism markers are common in patients with chronic kidney disease but there is no consensus on the association between these markers and clinical outcomes. This study investigated associations between mineral metabolism parameters and mortality in Chinese peritoneal dialysis (PD) patients. METHODS: This was a single-centre retrospective cohort study. Incident PD patients between 1 January 2006 and 31 December 2013 with baseline phosphate, albumin-corrected calcium, and calcium-phosphate product data were enrolled. Associations between these parameters and all-cause and cardiovascular mortality were assessed using multivariable-adjusted Cox models. RESULTS: Of 1662 patients (mean age: 47.4 ± 15.3 years), 59.3% were male and 23.8% had diabetes. Over a median 38.1 month (interquartile range: 21.3-59.7 months) follow-up period, 382 (23.0%) patients died. After adjusting for confounders, the higher serum phosphate level (>1.78 mmol/L) and calcium-phosphate product level (≥4.4 mmol2 /L2 ) were significantly associated with an increased risk for all-cause mortality (hazards ratio (HR) = 1.818, 95% CI = 1.379-2.396 and HR = 1.735, 95% CI = 1.261-2.386) and cardiovascular mortality (HR = 2.069, 95% CI = 1.428-2.998 and HR = 2.175, 95% CI = 1.450-3.262), respectively. While each 1 mmol/L higher baseline albumin-corrected calcium level was associated with an 14.3% (95% CI = 0.749-0.981) lower risk for all-cause mortality after adjusting for potential confounders. CONCLUSION: Abnormalities in mineral metabolism markers, particularly higher serum phosphate and calcium-phosphate product levels, at the commencement of PD were independently associated with increased all-cause and cardiovascular mortality in this cohort of PD patients.

The Effect of Increasing Dialysate Magnesium on Serum Calcification Propensity in Subjects with End Stage Kidney Disease: A Randomized, Controlled Clinical Trial.

BACKGROUND AND OBJECTIVES: Serum calcification propensity is a novel functional test that quantifies the functionality of the humeral system of calcification control. Serum calcification propensity is measured by T50, the time taken to convert from primary to secondary calciprotein particle in the serum. Lower T50 represents higher calcification propensity and is associated with higher risk of cardiovascular events and death in patients with ESKD. Increasing magnesium in serum increases T50, but so far, no clinical trials have investigated whether increasing serum magnesium increases serum calcification propensity in subjects with ESKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We conducted a single-center, randomized, double-blinded, parallel group, controlled clinical trial, in which we examined the effect of increasing dialysate magnesium from 1.0 to 2.0 mEq/L for 28 days compared with maintaining dialysate magnesium at 1.0 mEq/L on T50 in subjects undergoing hemodialysis for ESKD. The primary end point was the value of T50 at the end of the intervention. RESULTS: Fifty-nine subjects were enrolled in the trial, and of these, 57 completed the intervention and were analyzed for the primary outcome. In the standard dialysate magnesium group, T50 was 233±81 minutes (mean±SD) at baseline (mean of days -7 and 0) and 229±93 minutes at follow-up (mean of days 21 and 28), whereas in the high dialysate magnesium group, T50 was 247±69 minutes at baseline and 302±66 minutes at follow-up. The difference in T50 between the two groups at follow-up (primary analysis) was 73 minutes (between-group difference; 95% confidence interval, 30 to 116; P<0.001), and the between-group difference in serum magnesium was 0.88 mg/dl (95% confidence interval, 0.66 to 1.10; P=0.001). CONCLUSIONS: Increasing dialysate magnesium increases T50 and hence, decreases calcification propensity in subjects undergoing maintenance hemodialysis. PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_08_21_CJASNPodcast_18_9_B.mp3.

Scanning electron microscopy for blood micro-crystals in aortic stenosis patients.

BACKGROUND: Micro-crystals of calcium phosphate have been detected on the aortic valve of patients with aortic stenosis using scanning electron microscopy. It is not known whether crystalisation is specific to heart valve tissue or a general blood-derived process. METHODS: To this end we modified the method to determine whether calcium phosphate micro-crystals were present in the blood of patients with aortic stenosis. The method was first validated by adding synthetic calcium phosphate hydroxyapatite micro-crystals to healthy volunteer blood samples and determining the lower limit of detection. Then the method was used to examine the blood of 63 patients with echocardiographically confirmed aortic stenosis and 69 unaffected controls undergoing echocardiography for other reasons. Serum calcium and phosphate were measured and the calcium phosphate product compared in cases and controls. RESULTS: In the validation study, synthetic hydroxyapatite micro-crystals were identified down to a lower concentration limit of 0.008mg/mL. In the experimental study no particles were identified in any patient, with or without aortic stenosis, even though serum calcium phosphate was higher in cases compared with controls 2.6mmol/L (2.58-2.77) versus 2.47mmol/L (2.36-2.57), p = 0.005 for the difference. CONCLUSION: The results of our study confirm a positive association between serum calcium phosphate and aortic stenosis, but indicate that the calcium phosphate particles found in valve tissue do not precipitate freely in the blood.

Calcifediol (25-hydroxyvitamin D) improvement and calcium-phosphate metabolism of alendronate sodium/vitamin D3 combination in Chinese women with postmenopausal osteoporosis: a post hoc efficacy analysis and safety reappraisal.

BACKGROUND: Vitamin D (VD) insufficiency or deficiency is a frequent comorbidity in Chinese women with postmenopausal osteoporosis (PMO). The present study aimed to investigate 25-hydroxyvitamin D [25(OH) D] improvement and calcium-phosphate metabolism in Chinese PMO patients treated with 70 mg of alendronate sodium and 5600 IU of vitamin D3 (ALN/D5600). METHODS: Chinese PMO women (n = 219) were treated with 12-month ALN/D5600 (n = 111) or calcitriol (n = 108). Changes in 25(OH) D at month 12 were post hoc analyzed by the baseline 25 (OH) D status using the longitudinal analysis. The main safety outcome measures included serum calcium and phosphate and 24-h urine calcium, and the repeated measures mixed model was used to assess the frequencies of the calcium-phosphate metabolic disorders. RESULTS: Absolute change in mean serum 25(OH) D level was the greatest in VD-deficient patients and least in VD-sufficient patients at months six and 12 (both, P < 0.01). Serum calcium level remained significantly lower in the ALN/D5600 treatment group than in the calcitriol treatment group throughout the 12 months. Mean 24-h urine calcium slightly increased in the ALN/D5600 treatment group and significantly increased in the calcitriol treatment group (+ 1.1 and + 0.9 mmol/L at months six and 12; both, P < 0.05). Calcitriol treatment was associated with more frequent hypercalciuria at month six (9.4% vs. 18.5%, P = 0.05), but not at month 12 (12.3% vs. 13.0%). CONCLUSION: Baseline VD status predicted 25(OH) D improvement in PMO patients on 12-month ALN/D5600 treatment. The daily use of 0.25 µg of calcitriol was associated with more frequent hypercalciuria at month six, compared to ALN/5600 treatment, necessitating the safety re-evaluation of calcitriol at a higher dosage.

Underrecognition and Underestimation of Disturbances in Calcium-Phosphate Balance in Kidney Transplant Recipients.

Disturbances in mineral metabolism, namely chronic kidney disease-metabolic bone disease, became more profound with impairment of renal function. The aim of the study was to assess how often calcium, phosphate, alkaline phosphatase, and parathyroid hormone (PTH) were measured in kidney transplant recipients relative to hemodialyzed patients. In addition, prevalence of hypercalcemia defined as calcium concentration over 10.5 mg/dL was assessed. PATIENTS AND METHODS: We studied 200 kidney allograft recipients and 100 hemodialyzed patients. Calcium, phosphate, alkaline phosphatase, 25-hydroxy vitamin D, and PTH were obtained from outpatient charts. RESULTS: All the studied parameters were available in 100% of the hemodialyzed patients. In kidney allograft recipients, calcium and phosphate levels were available in 80%, alkaline phosphatase activity was available in 40%, PTH was available in less than 10%, and vitamin D was available in 1%. Hypercalcemia was present in 10% of hemodialyzed patients and in 5% of kidney allograft recipients. Vitamin D analogue was administered to 98% of hemodialyzed patients, whereas vitamin D was administered to 28% of kidney allograft recipients, particularly those with impaired kidney function. In conclusion, calcium and phosphate are seldom assessed on an outpatient basis in kidney allograft recipients, making the diagnosis and treatment of secondary hyperparathyroidism in this population difficult. Care of kidney transplant recipients could be substantially improved, particularly in regard to chronic kidney disease-metabolic bone disease, when regular check-ups for calcium-phosphate balance are implemented and proper treatment could be introduced to prevent further chronic kidney disease-metabolic bone disease.

Predictors of Renal Function and Calcifications in Primary Hyperparathyroidism: A Nested Case-Control Study.

Context: Some patients with primary hyperparathyroidism (PHPT) develop renal calcifications. Investigation of urinary and nonurinary risk factors are essential. Objective: We aimed to study the prevalence and potential biochemical predictors of renal calcifications. Design: Nested case-control study. Setting: University hospital. Participants: We identified 792 patients with PHPT from 2005 to 2015. We used biochemical data to validate the diagnosis of PHPT. Main Outcome Measures: The prevalence of renal calcifications defined as nephrolithiasis or nephrocalcinosis assessed by a routine CT scan at the time of diagnosis. Results: A total of 792 patients with PHPT were identified among whom 617 patients (78%) had a CT scan preformed. We found a prevalence of renal calcifications of 23%, equally frequent between sexes. A total of 76 patients (12%) had nephrolithiasis and 75 patients (12%) had nephrocalcinosis where 7 patients (1%) had both nephrolithiasis and nephrocalcinosis. Compared with patients without renal calcifications, patients with renal calcifications had significantly higher levels of ionized calcium, parathyroid hormone, and 24-hour calcium excretion (Pall < 0.01). Patients with nephrocalcinosis had higher plasma levels of phosphate and a higher calcium-phosphate product compared with patients with nephrolithiasis (Pall < 0.05). Impaired renal function (estimated glomerular filtration rate <60 mL/min) was observed in 12% of patients. However, no differences in renal function were observed between those with and without renal calcifications. Conclusion: Renal calcifications are frequent in patients with PHPT and are associated with the severity of the disease. Impaired renal function is also common in PHPT, but renal function was not associated with renal calcifications.

Daily variability in serum levels of calciprotein particles and their association with mineral metabolism parameters: A cross-sectional pilot study.

AIM: Calciprotein particles (CPPs), colloidal protein-mineral nanoparticles composed of solid-phase calcium phosphate and serum protein fetuin-A found in blood, are emerging as a novel component of chronic kidney disease-mineral and bone disorder (CKD-MBD). The relationship of CPPs with factors known to underlie the CKD-MBD pathophysiology is not well known.The aim of this study is to examine daily variations in CPPs as well as their association with mineral metabolism parameters in normal individuals and early-stage CKD patients. METHODS: Twenty subjects (10 healthy adults, 10 diabetic patients) were enrolled. Serum CPP Fetuin-A was measured and analyzed in relation to clinical parameters. RESULTS: Estimated glomerular filtration rates (eGFR) were 103 ± 11 and 75 ± 24 mL/min per 1.73 m2 in healthy adults and diabetic patients, respectively. Serum CPP Fetuin-A (g/L) were elevated at postprandial 2 h in diabetic patients. Furthermore, serum CPP Fetuin-A were inversely correlated with eGFR and serum 1,25-dihydroxyvitamin D3 and magnesium levels and were positively correlated with serum fibroblast growth factor-23. CONCLUSIONS: These findings indicated that serum CPP Fetuin-A were affected by food intake and may contribute to the pathophysiology of mineral metabolism in subjects with normal and moderately impaired renal function.

Secondary hyperparathyroidism among Nigerians with chronic kidney disease.

BACKROUND: Secondary hyperparathyroidism (SHPT) is a manifestation of chronic kidney disease mineral bone disorder (CKD-MBD). SHPT is common in patients with chronic kidney disease (CKD) and is associated with significant morbidity and mortality. METHODS: A cross- sectional descriptive study involving 230 patients with CKD. RESULTS: The mean age of the study population was 44.17±15.24 years. The median intact parathyroid hormone and alkaline phosphatase levels were 96pg/ml (range 4-953pg/ml) and 88 iu/l (range 10-800 iu/l) respectively. The mean (with standard deviation) calcium, serum phosphate, calcium phosphate product and haemoglobin levels were 2.22±0.29mmol/l, 1.8±0.62mmol/l, 3.94±1.42mmol2/l2 and 9.90±1.87g/dl respectively. Majority of patients had advanced CKD with 70.3% of patients in stage G5. The prevalence rates of SHPT, hypocalcaemia, hyperphosphataemia, elevated alkaline phosphatase and elevated calcium phosphate product were 55.2%, 34.8%, 66.1%, 42.2% and 25.2% respectively.Univariate analysis revealed that SHPT was associated with hypocalcaemia, hyperphosphataemia, elevated alkaline phosphatase, proteinuria, anaemia, hypertension, left ventricular hypertrophy and stage of kidney disease; being worse with advancing kidney disease. Independently associated with SHPT were hypocalcaemia (OR=4.84), hyperphosphataemia (OR=3.06), and elevated alkaline phosphatase (OR=2.04). CONCLUSION: The prevalence of SHPT in CKD is high, occurs early and is independently associated with hypocalcaemia, hyperphosphataemia and elevated alkaline phosphatase. The prevalence of SHPT also increases with worsening renal function.

Calcium Phosphate Product Is Associated with Subclinical Carotid Atherosclerosis in Type 2 Diabetes.

AIMS: To assess whether circulating 25-hydroxyvitamin D3 (25OHD) and mineral metabolism-related factors (serum phosphate, calcium, and parathormone) are associated with subclinical carotid atherosclerosis (SCA), defined as the presence of carotid atherosclerotic plaques (main study outcome), in patients with type 2 diabetes mellitus (T2DM) without kidney disease or previous cardiovascular disease. METHODS: We undertook a post hoc analysis of a cross-sectional study in adults with T2DM in whom we evaluated SCA. A total of 303 subjects with T2DM were included. Clinical variables and carotid ultrasound imaging were obtained. RESULTS: We found no association of 25OHD with the presence of SCA. However, calcium phosphate (CaP; mg2/dL2) product was positively associated with the presence of carotid plaques (ORadj = 1.078; 95% CI: 1.017-1.142). An inverse association was observed between higher levels of 25OHD (≥30 ng/mL versus <20 ng/mL concentrations) and common carotid intima-media thickness (cIMT; mm) (ßadj ± SE = -0.055 ± 0.024). We conclude that the CaP product is independently associated with the presence of established subclinical carotid atherosclerosis in patients with T2DM.

A novel pharmacodynamic assay to evaluate the effects of crystallization inhibitors on calcium phosphate crystallization in human plasma.

Cardiovascular calcification (CVC) is a progressive complication of chronic kidney disease and a predictor of CV events and mortality. The use of biomarkers to predict CV risk and activities of potential or current treatment drugs in these patients could have a crucial impact on therapeutic approaches. Our aim was to develop a novel assay for measurement of the rate of calcium phosphate crystallization in human plasma and provide a tool to evaluate the effects of crystallization inhibitors. The efficacy of inhibitors was determined by adding inhibitory compounds (polyphosphates, fetuin-A, sodium thiosulfate or citrate) to control samples. The assay was additionally validated for SNF472, an experimental formulation of phytate being developed for the treatment of calciphylaxis and CVC in patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD). The method was repeatable and reproducible. The plasma crystallization rate was reduced up to 80% in a concentration-dependent manner following treatment with inhibitors in vitro, among which SNF472 was the most potent. This method appears beneficial in evaluating and discriminating between inhibitory activities of compounds such as polyphosphates on calcium phosphate crystallization, which present a novel therapeutic approach to treat CVC in ESRD patients.

Coupling between phosphate and calcium homeostasis: a mathematical model.

We developed a mathematical model of calcium (Ca) and phosphate (PO4) homeostasis in the rat to elucidate the hormonal mechanisms that underlie the regulation of Ca and PO4 balance. The model represents the exchanges of Ca and PO4 between the intestine, plasma, kidneys, bone, and the intracellular compartment, and the formation of Ca-PO4-fetuin-A complexes. It accounts for the regulation of these fluxes by parathyroid hormone (PTH), vitamin D3, fibroblast growth factor 23, and Ca2+-sensing receptors. Our results suggest that the Ca and PO4 homeostatic systems are robust enough to handle small perturbations in the production rate of either PTH or vitamin D3 The model predicts that large perturbations in PTH or vitamin D3 synthesis have a greater impact on the plasma concentration of Ca2+ ([Ca2+]p) than on that of PO4 ([PO4]p); due to negative feedback loops, [PO4]p does not consistently increase when the production rate of PTH or vitamin D3 is decreased. Our results also suggest that, following a large PO4 infusion, the rapidly exchangeable pool in bone acts as a fast, transient storage PO4 compartment (on the order of minutes), whereas the intracellular pool is able to store greater amounts of PO4 over several hours. Moreover, a large PO4 infusion rapidly lowers [Ca2+]p owing to the formation of CaPO4 complexes. A large Ca infusion, however, has a small impact on [PO4]p, since a significant fraction of Ca binds to albumin. This mathematical model is the first to include all major regulatory factors of Ca and PO4 homeostasis.

A novel fluorescent probe-based flow cytometric assay for mineral-containing nanoparticles in serum.

Calciprotein particles, nanoscale aggregates of insoluble mineral and binding proteins, have emerged as potential mediators of phosphate toxicity in patients with Chronic Kidney Disease. Although existing immunochemical methods for their detection have provided compelling data, these approaches are indirect, lack specificity and are subject to a number of other technical and theoretical shortcomings. Here we have developed a rapid homogeneous fluorescent probe-based flow cytometric method for the detection and quantitation of individual mineral-containing nanoparticles in human and animal serum. This method allows the discrimination of membrane-bound from membrane-free particles and different mineral phases (amorphous vs. crystalline). Critically, the method has been optimised for use on a conventional instrument, without the need for manual hardware adjustments. Using this method, we demonstrate a consistency in findings across studies of Chronic Kidney Disease patients and commonly used uraemic animal models. These studies demonstrate that renal dysfunction is associated with the ripening of calciprotein particles to the crystalline state and reveal bone metabolism and dietary mineral as important modulators of circulating levels. Flow cytometric analysis of calciprotein particles may enhance our understanding of mineral handling in kidney disease and provide a novel indicator of therapeutic efficacy for interventions targeting Chronic Kidney Disease-Mineral Bone Disorder.

Requests of laboratory tests for the diagnosis and management of calcium-phosphate disorders in Spain.

BACKGROUND: Knowledge about the variability in the request of calcium-phosphate metabolism laboratory tests in primary care is important to design strategies to improve health system efficiency. AIM: To compare the inter-practice variability in calcium-phosphate metabolism laboratory tests requested by general practitioners from diverse regions across Spain. MATERIAL AND METHODS: One hundred and forty one clinical laboratories were invited to participate in an observational cross-sectional study. They informed the number of serum calcium, phosphate, parathyroid hormone and 25-hydroxyvitamin D requested by general practitioners. Appropriateness indicators were calculated as number of test requests per 1,000 inhabitants and ratio of related tests requests. The differences according to hospital setting, region and type of management were analyzed. RESULTS: We recruited 76 laboratories (17,679,195 inhabitants). General practitioners requested 3,260,894 calcium-phosphate metabolism tests. The rate of request ranged from 2.97 per 1,000 inhabitants for 25-hydroxyvitamin D to 98.89 per 1,000 inhabitants for calcium. The rates of request for calcium, phosphate, parathyroid hormone in some areas were 30, 100 and 340 times higher than in other areas. Parathyroid hormone and 25-hydroxyvitamin D were highly requested in private management areas. There were also differences in phosphate, parathyroid hormone and 25-hydroxyvitamin D requesting between regions across Spain. CONCLUSIONS: The high variability observed is difficult to explain by differences in patient case mix between regions. Depending on the area, calcium could be under requested to detect primary hyperparathyroidism.

High Prevalence of Hyperhomocysteinemia and Its Association with Target Organ Damage in Chinese Patients with Chronic Kidney Disease.

Hyperhomocysteinemia (HHcy) is recognized as a risk factor for cardiovascular disease. However, the prevalence of HHcy and its role in association with target organ damage in patients with chronickidney disease (CKD) are not well understood. This cross-sectional study included 1042 CKD patients who were admitted to our hospital. Patients were divided into two groups: hyperhomocysteinemia and normohomocysteinemia. Multivariable linear regression analyses were used to evaluate the association between plasma homocysteine and renal/cardiovascular parameters. The prevalence of HHcy in patients with CKD was 52.78%, and the prevalence in CKD stage 1, stage 2, stage 3, stage 4 and stage 5 patients was 10.73%, 29.22%, 58.71%, 75.23% and 83.75%, respectively. Patients with HHcy had higher incidences of renal damage, left ventricular hypertrophy, left ventricular diastolic dysfunction and abnormal carotid intima-media thickness compared with patients with normohomocysteinemia (p < 0.05), while multivariable linear regression analyses showed plasma homocysteine was only associated with the estimated glomerular filtration rate (eGFR). eGFR, uric acid, albumin, gender, hemoglobin and calcium×phosphate were associated with levels of plasma homocysteine in these CKD patients. The prevalence of HHcy in Chinese patients with CKD was high, and serum homocysteine levels were associated with impaired renal function in these patients.

Requests of laboratory tests for the diagnosis and management of calcium-phosphate disorders in Spain / Solicitud de pruebas de laboratorio para el diagnóstico y manejo de los desórdenes del metabolismo fosfocálcico en España

Background: Knowledge about the variability in the request of calcium-phosphate metabolism laboratory tests in primary care is important to design strategies to improve health system efficiency. Aim: To compare the inter-practice variability in calcium-phosphate metabolism laboratory tests requested by general practitioners from diverse regions across Spain. Material and Methods: One hundred and forty one clinical laboratories were invited to participate in an observational cross-sectional study. They informed the number of serum calcium, phosphate, parathyroid hormone and 25-hydroxyvitamin D requested by general practitioners. Appropriateness indicators were calculated as number of test requests per 1,000 inhabitants and ratio of related tests requests. The differences according to hospital setting, region and type of management were analyzed. Results: We recruited 76 laboratories (17,679,195 inhabitants). General practitioners requested 3,260,894 calcium-phosphate metabolism tests. The rate of request ranged from 2.97 per 1,000 inhabitants for 25-hydroxyvitamin D to 98.89 per 1,000 inhabitants for calcium. The rates of request for calcium, phosphate, parathyroid hormone in some areas were 30, 100 and 340 times higher than in other areas. Parathyroid hormone and 25-hydroxyvitamin D were highly requested in private management areas. There were also differences in phosphate, parathyroid hormone and 25-hydroxyvitamin D requesting between regions across Spain. Conclusions: The high variability observed is difficult to explain by differences in patient case mix between regions. Depending on the area, calcium could be under requested to detect primary hyperparathyroidism.

Objetivo: Conocer la variabilidad en la solicitud de pruebas de laboratorio en atención primaria es importante para diseñar estrategias que mejoren la eficiencia del sistema de salud. La propuesta de este estudio fue comparar la variabilidad en la solicitud de pruebas para la evaluación del metabolismo fosfocálcico por médicos de atención primaria de diversas regiones de España. Material y Método: Se invitó a participar a 141 laboratorios clínicos de diversas regiones españolas. Completaron una encuesta con el número de determinaciones de calcio, fósforo, hormona paratiroidea y 25-hidroxivitamina D solicitadas por médicos de atención primaria de sus áreas. Se calcularon las tasas en relación a la población y se construyeron indicadores de adecuación. Los resultados se compararon por características del hospital, región y tipo de gestión. Resultados: Obtuvimos los datos de 76 laboratorios (17.679.195 habitantes). Los médicos de atención primaria solicitaron 3.260.894 pruebas de metabolismo fosfocálcico. La tasa de solicitud varió de 2,97 por 1.000 habitantes de 25-hidroxivitamin D a 98,89 por 1.000 habitantes de calcio. Las tasas de calcio, fósforo, hormona paratiroidea en algunas áreas fue 30, 100 y 340 veces más alta respecto a otras. Hormona paratiroidea y 25-hidroxivitamina D fueron más solicitadas significativamente en hospitales con gestión privada. También hubo diferencias en fósforo, hormona paratiroidea y 25-hidroxivitamina D solicitas entre distintas regiones de España. Discusión: La alta variabilidad observada es difícil de explicar por las diferencias de las características de los pacientes. Dependiendo de la región podría haber una infra solicitud para la detección del hiperparatiroidismo primario.