Serum phosphate optimal timing and range associated with patients survival in haemodialysis: the COSMOS study.

BACKGROUND: Serum phosphate is a key parameter in the management of chronic kidney disease-mineral and bone disorder (CKD-MBD). The timing of phosphate measurement is not standardized in the current guidelines. Since the optimal range of these biomarkers may vary depending on the duration of the interdialytic interval, in this analysis of the Current management of secondary hyperparathyroidism: a multicentre observational study (COSMOS), we assessed the influence of a 2- (midweek) or 3-day (post-weekend) dialysis interval for blood withdrawal on serum levels of CKD-MBD biomarkers and their association with mortality risk. METHODS: The COSMOS cohort (6797 patients, CKD Stage 5D) was divided into two groups depending upon midweek or post-weekend blood collection. Univariate and multivariate Cox's models adjusted hazard ratios (HRs) by demographics and comorbidities, treatments and biochemical parameters from a patient/centre database collected at baseline and every 6 months for 3 years. RESULTS: There were no differences in serum calcium or parathyroid hormone levels between midweek and post-weekend patients. However, in post-weekend patients, the mean serum phosphate levels were higher compared with midweek patients (5.5 ± 1.4 versus 5.2 ± 1.4 mg/dL, P < 0.001). Also, the range of serum phosphate with the lowest mortality risk [HR ≤ 1.1; midweek: 3.5-4.9 mg/dL (95% confidence interval, CI: 2.9-5.2 mg/dL); post-weekend: 3.8-5.7 mg/dL (95% CI: 3.0-6.4 mg/dL)] showed significant differences in the upper limit (P = 0.021). CONCLUSION: Midweek and post-weekend serum phosphate levels and their target ranges associated with the lowest mortality risk differ. Thus, clinical guidelines should consider the timing of blood withdrawal when recommending optimal target ranges for serum phosphate and therapeutic strategies for phosphate control.

Applications and functions of food-grade phosphates.

Food-grade phosphates are used in the production of foods to function as buffers, sequestrants, acidulants, bases, flavors, cryoprotectants, gel accelerants, dispersants, nutrients, precipitants, and as free-flow (anticaking) or ion-exchange agents. The actions of phosphates affect the chemical leavening of cakes, cookies, pancakes, muffins, and doughnuts; the even melt of processed cheese; the structure of a frankfurter; the bind and hydration of delicatessen meats; the fluidity of evaporated milk; the distinctive flavor of cola beverages; the free flow of spice blends; the mineral content of isotonic beverages; and the light color of par-fried potato strips. In the United States, food-grade phosphates are generally recognized as safe, but use levels have been defined for some foods by the Code of Federal Regulations, specifically Titles 9 and 21 for foods regulated by the U.S. Department of Agriculture (USDA) and the U.S. Food and Drug Administration (FDA), respectively. Standards for food purity are defined nationally and internationally in sources such as the Food Chemicals Codex and the Joint Food and Agriculture Organization and World Health Organization (FAO/WHO) Expert Committee on Food Additives.

Current status of homogeneity and stability of the reference materials for nutrients in seawater.

The development of Reference Materials for Nutrients in Seawater (RMNS) has been in progress since 1993. When RMNS were produced for nitrate, silicate, and phosphate, their initial homogeneities were as low as 0.1 to 0.2% in samples of high-nutrient seawater, such as deep water from the Pacific Ocean. The relative standard uncertainties associated with instability during long-term (4.8 years) storage were approximately 0.2, 0.2, and 0.4% for nitrate, silicate, and phosphate, respectively. No instability was observed for 1.9 to 6.4 years based on the ISO Guide 35:2006 criteria; however, the relative standard uncertainties associated with instability during long-term storage were larger than the initial homogeneities of RMNS. RMNS produced by state-of-the-art techniques are currently available for global use to improve the comparability of nutrients data in the open ocean and, as discussed here, are reliable candidates to be used for certified reference materials.

A recreational water quality index using chemical, physical and microbiological parameters.

PURPOSE: The aim of this paper was to develop a new recreational water quality index (RWQI) as a tool to ensure the health of swimmers and to take practical decisions. METHODS: RWQI was elaborated with epidemiological data, and we carried out an exhaustive study of the different guidelines for recreational waters proposed by different organisations around the world. Different parameters were chosen, considering, as a priority, the swimmer's contact and the possibility of ingestion of water during the recreational activity. Furthermore, rating curves were established for pH, chemical oxygen demand, nitrate, phosphate, detergents, enterococci, total coliforms, faecal coliforms and Escherichia coli. RESULTS AND CONCLUSIONS: The index was applied to the data set on water quality of the Potrero de los Funes River (San Luis, Argentina), generated during 2 years (2009-2010). Following the RWQI values classification, most of the Potrero de los Funes water samples fell in the good quality range during the study period.

Method for the in situ calibration of a passive phosphate sampler in estuarine and marine waters.

Passive samplers for phosphate were calibrated in the laboratory over a range of flow velocities (0-27 cm s(-1)) and ionic strengths (0-0.62 mol kg(-1)). The observed sampling rates were between 0.006 and 0.20 L d(-1). An empirical model allowed the estimation of these sampling rates with a precision of 8.5%. Passive flow monitors (PFMs), based on gypsum dissolution rates, were calibrated for the same range of flow velocities and ionic strength. Mass loss rates of the PFMs increased with increasing ionic strength. We demonstrate that this increase is quantitatively accounted for by the increased gypsum solubility at higher ionic strengths. We provide a calculation scheme for these solubilities for an environmentally relevant range of temperatures and salinities. The results imply that co-deployed PFMs can be used for estimating the flow effect on the in situ sampling rates of the phosphate samplers, and we expect that the same may hold for other passive samplers.

Preparation and evaluation of candidate certified reference materials (CRMs) for nutrients in seawater.

Certified reference materials (CRMs) are an essential part of the quality assurance (QA) necessary for the reliable analytical measurement of nutrients in seawater. The CRMs currently available for these analyses are not matrix matched to marine samples. QUASIMEME routinely produces test materials for the nutrients in seawater and nutrients in estuarine water and low-salinity open water Laboratory Performance Studies (LPS) that are both homogeneous and stable. QUASIMEME, in conjunction with Eurofins Scientific, Denmark have produced two reference materials (RMs). The homogeneity testing and preliminary stability studies were carried out by QUASIMEME, and the results are presented in this article. Participants of the QUASIMEME LPS who demonstrated satisfactory long-term performance for the analysis of nutrients in seawater and nutrients in estuarine water and low-salinity open water were invited to take part in the certification exercise. Twenty laboratories returned data, a summary of which is also presented. The certification and long-term stability testing and additional data analysis were carried out by Eurofins Scientific, Denmark, and are outwith the scope of this article and not reported here. Eurofins Scientific, Denmark have marketed these RMs as part of their range of VKI Reference Materials (further information is available from eurofins@eurofins.dk).

Risk assessment of physico-chemical contaminants in groundwater of Pettavaithalai area, Tiruchirappalli, Tamilnadu - India.

A study was carried out in Pettavaithalai area to evaluate the current status of physico-chemical contaminants and their sources in groundwater. Groundwater samples collected from pettavaithalai area in 15 different stations were analyzed every alternative months over a period of two years from August 2000 to June 2002. A sugar mill is situated at the heart of the study area. Three profiles (profile A, B and C) were selected based on the direction in which the sugar mill effluent flows. In each profile five samples were collected from five different station at a regular distance of about 1 Km. The physico-chemical parameters such as pH, EC TDS, TH, NO3, SO4, PO4, Na, K, Ca, Mg, DO, BOD and COD have been analyzed. The results showed that among the three profiles, many of the estimated physico-chemical parameters of profile C were very high when compared to profile B and A which indicates the poor quality of the groundwater around this area.

An improved method for a rapid determination of phytase activity in animal feed.

The current direct colorimetric assay for phytase activity in feeds has interference from high P background and other factors. Our objective was to develop a rapid and reliable spin column method to accurately determine phytase activity in feed ingredients or complete diets. After the feed sample was extracted by stirring in 0.2 M citrate buffer, pH 5.5, for 30 min at room temperature, the oily layer of the supernatant fraction was removed by passing through an acrodisc syringe filter (0.45-microm HT Tuffryn membrane, Gelman Laboratory, Ann Arbor, MI). The filtrate was then loaded onto a spin column (MW cutoff 30,000, Millipore, Bedford, MA) to remove free phosphate before the phytase activity assay. Compared with the direct assay, this new procedure improved both accuracy and reproducibility. When diets contained phytase at 0 to 1,500 U/kg (as fed), the CV for multiple assays of the same samples (n = 6) by the new method ranged from 1 to 6% compared with 28 to 39% by the direct method. A linear relationship was found between the added phytase activity in practical diets and the analyzed activity by the new method (r2 = 0.99; P < 0.01). In conclusion, the spin column method is an improved assay for phytase activity in animal feed, and may be used for quality control of phytase supplementation.

Bismuth citrate in the quantification of inorganic phosphate and its utility in the determination of membrane-bound phosphatases.

This paper describes a rapid and sensitive method to determine inorganic phosphate, even in the presence of labile organic phosphate compounds and large quantities of proteins. The method eliminates the use of sodium arsenite, a highly toxic compound, substituting bismuth citrate for it to stabilize the phosphomolybdic acid complex formed during the interaction of inorganic phosphate and molybdate reduced by ascorbic acid. This method has also been adapted to microplates and has been used to determine the activities of Na/K ATPase and alkaline phosphatase of intestinal basolateral and luminal plasma membranes.

Influence of poultry manure on phosphorus availability and the standard phosphate requirement of crop estimated from quantity-intensity relationships in different soils.

Twelve samples comprising of non-calcareous, calcareous and acidic soils were used to study P availability parameters and standard phosphate requirement (SPR) in the presence and absence of poultry manure (PM). Adsorption of P and phosphate potential decreased while Olsen extractable P increased by PM addition, the extent varying with the type of soil. The calculated SPR to attain soil solution concentration of 0.2 microg P ml(-1) was invariably higher in fine textured soils. Acid and calcareous soils registered higher SPR compared to non-calcareous soils. PM addition lowered the SPR in all the soils. The observed P supplementation through PM ranged from 11.6% to 100% signifying no fertilizer P need in the latter. Calibration curves were drawn for calculating the SPR for a given soil solution P concentration without and with the addition of PM.

Application of internal standardization to rapid coprecipitation technique using lanthanum phosphate for flame atomic absorption spectrometric determination of iron and lead.

By applying an internal standardization, we could use a rapid coprecipitation technique using lanthanum phosphate as a coprecipitant for preconcentration of iron(III) and lead in their flame atomic absorption spectrometric determination. Indium as an internal standard was added to the initial sample solution together with lanthanum and phosphoric acid; the coprecipitation of iron(III) and lead was then carried out at pH about 3. After measuring the atomic absorbances of iron, lead, and indium in the final sample solution, we determined the contents of iron(III) and lead in the original sample solution by using the internal standardization with indium. In this method, complete collection of the precipitate was not required after the coprecipitation of iron(III), lead, and indium, because the ratio of the recovery of iron(III) or lead to that of indium was almost constant regardless of the recovery of the precipitate. This method was simple and rapid, and was available for the determination of 2-300 micrograms L-1 of iron(III) and 5-400 micrograms L-1 of lead in some water samples.

Utilization of the skin attachment model to determine the antibacterial efficacy of potential carcass treatments.

Two experiments (EXP), utilizing the skin attachment model (SAM), were conducted to determine the bactericidal activity of six potential carcass disinfectants [EXP 1: 20, 400, and 800 ppm sodium hypochlorite; EXP 2: 5% acetic acid (AA), 8% trisodium phosphate (TSP), and 1% sodium metabisulfite (SS)] during simulated scalder (50 C for 2 min), chiller (0 C for 60 min), or post-process dip (23 C for 15 s) application. Efficacies of treatments were determined against populations of Salmonella typhimurium that were "loosely" or "firmly" attached to chicken breast skin (10 cm diameter). For comparison, activity of the six disinfectants was also determined against S. typhimurium in aqueous suspension. All disinfectants except SS reduced numbers of freely suspended S. typhimurium by > or = 4.5 log10 cfu/mL. The sodium metabisulfite did not reduce populations of salmonellae. In both EXP, there were disinfectant by application interactions (P < 0.05) on activity against loosely and firmly attached cells. Sodium hypochlorite at 20 ppm had little activity regardless of application, whereas higher levels were more effective (P < 0.001), particularly in the chiller application, in which loosely and firmly attached populations were reduced by 2.3 to 2.5 and 1.3 to 1.9 log10 cfu per skin, respectively. In EXP 2, SS showed no activity regardless of application. Trisodium phosphate was similarly effective (reduction by 1.2 to 1.8 log10 cfu per skin) in all applications (P > 0.05). In contrast, AA activity was affected by the application method (P < 0.05). Against loosely attached cells, AA was most effective in the chiller application (2.5 log10 reduction), whereas against firmly attached cells, AA was effective only in the scalder application (2.0 log10 reduction). Attachment of S. typhimurium to poultry skin apparently increased the ability of the bacteria to resist various disinfectants, and efficacy was influenced by extent of attachment of bacteria to skin and method of disinfectant application.

A survey of the values of clinical chemistry parameters obtained for a common rat blood sample in ninety-eight Japanese laboratories.

A control survey was conducted to check the accuracy of automated analyzers used in the evaluation of clinical chemistry parameters in nonclinical toxicology studies. Pooled serum samples from male Sprague-Dawley rats were delivered refrigerated to each facility 98 laboratory facilities throughout Japan within 18 hours after sample preparation and analyzed. Commercially available normal human serum samples from a single lot were also analyzed at the same time. Survey results were divided into three categories. (1) Parameters with small coefficient of variation (CV) values for both rat and human serum samples included protein, glucose, cholesterol (CHO), urea nitrogen (UN), sodium (Na), potassium (K), chloride (Cl), calcium (Ca), and inorganic phosphate (IP). Definition of normal values in rats should be straight forward for these parameters. (2) Parameters with large CV values, but with a relatively good correlation between rat and human values include triglycerides (TG), glutamic oxaloacetic transaminase/aspartate aminotransferase (GOT/AST), glutamic pyruvic transaminase/alanine aminotransferase (GPT/ALT), and alkaline phosphatase (ALP). Measurements based on different principles gave different mean values, and this values contributed to the increase in CV values. Assessment of normal values would require a consideration of the measurement principles. (3) Parameters with large CV values only in rat serum samples included albumin (albumin/globulin ratio: A/G ratio), creatinine (CRE), and total bilirubin(BIL). Reactivity was different in rat albumin (ALB), depending on the reagents used. This difference needs to be corrected with values available by electrophoresis, or adjusted by rat ALB values, because of the lack of an appropriate measurement method. The enzyme method gave low values for rat CRE, which suggests the need for further examination of this method. The BIL values were extremely low in rat samples. It seems to be necessary to select appropriate methods to measure clinical pathology parameters correctly for rats. There was no deviation in values due solely to the mechanical operations of the analytical equipment. Non-standard initial settings of the equipment (equipment originally intended for human samples, but now applied to animal samples) was the main cause of the wide range of analytical values seen.

Method comparison for calcium determination by flame atomic absorption spectrophotometry in the presence of phosphate.

We investigated the suppressive effects of phosphate on calcium determinations with lanthanum-air/acetylene and potassium-nitrous oxide/acetylene methods, and we evaluated the ability of these methods to meet the suggested analytical goals for urine samples. The 20 g/L La-air/acetylene method was the most nearly accurate for predicting the actual calcium concentrations (t-test value = -0.042), followed by the 2 g/L K-nitrous oxide/acetylene method (t-test value = 0.450), 10 g/L La-air/acetylene (t-test value = -0.733), and finally 5 g/L La-air/acetylene (t-test value = -2.446). The dilution used significantly influences the apparent calcium concentration measured with the La-air/acetylene methods.

Type III gold alloy complete crowns cast in a phosphate-bonded investment.

A phosphate-bonded investment and a calcium sulphate-bonded investment were evaluated for the surface smoothness and marginal fit they impart to type III gold castings. The phosphate-bonded investment was used with burnout temperatures of 900 degrees F and 1,300 degrees F. The results of this study lead to the following conclusions: 1. The marginal fit with the phosphate-bonded investment method was superior to that obtained with the calcium sulphate-bonded investment. 2. Surface roughness was greater for the castings made with the phosphate-bonded investment when measured with SEM photographs and visual observation. 3. The phosphate bonded-investment increased the incidence of nodules on the surface of the castings. 4. No correlation was demonstrated between marginal fit and surface roughness or the incidence of nodules on the castings.