Variability between laboratories performing coagulation tests with identical platforms: a nationwide evaluation study.

BACKGROUND: While the assessment of analytical precision within medical laboratories has received much attention in scientific enquiry, the degree of as well as the sources causing variation between them remains incompletely understood. In this study, we quantified the variance components when performing coagulation tests with identical analytical platforms in different laboratories and computed intraclass correlations coefficients (ICC) for each coagulation test. METHODS: Data from eight laboratories measuring fibrinogen twice in twenty healthy subjects with one out of 3 different platforms and single measurements of prothrombin time (PT), and coagulation factors II, V, VII, VIII, IX, X, XI and XIII were analysed. By platform, the variance components of (i) the subjects, (ii) the laboratory and the technician and (iii) the total variance were obtained for fibrinogen as well as (i) and (iii) for the remaining factors using ANOVA. RESULTS: The variability for fibrinogen measurements within a laboratory ranged from 0.02 to 0.04, the variability between laboratories ranged from 0.006 to 0.097. The ICC for fibrinogen ranged from 0.37 to 0.66 and from 0.19 to 0.80 for PT between the platforms. For the remaining factors the ICC's ranged from 0.04 (FII) to 0.93 (FVIII). CONCLUSIONS: Variance components that could be attributed to technicians or laboratory procedures were substantial, led to disappointingly low intraclass correlation coefficients for several factors and were pronounced for some of the platforms. Our findings call for sustained efforts to raise the level of standardization of structures and procedures involved in the quantification of coagulation factors.

The 500 Ma-old Thyon metagranite: A new A-type granite occurrence in the western Penninic Alps (Wallis, Switzerland)

The Thyon metagranite is located in the frontal part of the Siviez-Mischabel Nappe, in the western Penninic Alps. It is intrusive in a polymetamorphic banded volcanic complex as leucocratic concordant sills with pseudoaplitic rims. A distinct metamorphic schistosity is defined by dark-green Fe-rich biotite. Abundant mesoperthites, chess-board albite and low microcline are presumably related to magmatic stages and/or greenschist-facies metamorphic retrogression. Major, trace element and REE geochemistry, zircon typology, Y and Nb-bearing accessory minerals such as fergusonite and euxenite, all point to a metaluminous to peraluminous alkaline A-type granite. High-precision U-Pb zircon dating yielded a sub-concordant age of 500 +3/-4 Ma. The Thyon metagranite is the third record of a Cambro-Ordovician alkaline magmatic activity in the Alps. As A-type granitic magmatism is common in post-orogenic to anorogenic extensional tectonic regime, the Thyon intrusion could mark the transition between the Cadomian and the Caledonian orogenies.

Occupational exposure to beryllium in Switzerland : exposed workers and occupations at risk

Introduction: Beryllium (Be) is increasingly used in various industrial applications. Occupational exposure to Be may lead to chronic beryllium disease (CBD), a pulmonary granulomatous disorder closely similar to sarcoidosis, which develop in 1 to 15% of exposed workers. Although Switzerland is one of the major Be importers worldwide, little information is available about occurrence of exposure and the number of workers exposed in this country. Objectives: 1) evaluate the number of workers potentially exposed to Be in Switzerland; 2) construct a screening tool to allow potential Be exposure detection in a clinical setting. Methods: After identification of industrial sectors involving beryllium exposure based on expert reports and scientific literature, an estimation of the number of workers employed in these relevant industries was made using data from the Swiss federal population census and registries of economic activities. A second analysis was performed to estimate the fraction of workers really exposed to Be in each industrial sector. This adjustment was made according to the results of a French survey (INRS, Institut National de Recherche et de Sécurité) conducted by questionnaire addressed to 4500 companies in relevant industries on their use of beryllium and other issues such as percentage of employees really exposed. These realistic data were used to develop a self-administrated screening questionnaire allowed to identify patients with possible Be exposure. Results: In Switzerland, the number of workers employed in industries using Be was nearly 150 000. The estimated number of workers exposed to beryllium in these industries ranged from 2000 to 4000. Relevant sectors were: microengineering, precision turning, watchmaking and metal waste treatment and recycling. The validation of the self-administrated questionnaire containing a list of jobs and leisure activities associated with potential Be exposure is in progress within the framework of a national study. Conclusions: The number of workers potentially exposed to Be in Switzerland is rather high compared to estimations for other industrialized countries and might constitute an underestimated occupational health problem. Undetected Be exposure in patients with sarcoidosis may occur and result in misdiagnosis. Once validated, the self-administrated questionnaire could be used by clinicians to screen for Be exposure in patients with granulomatous lung disorders.

Heated Optical Fiber for Distributed Soil-Moisture Measurements: A Lysimeter Experiment

An Actively Heated Fiber Optics (AHFO) method to estimate soil moisture is tested and the analysis technique improved on. The measurements were performed in a lysimeter uniformly packed with loam soil with variable water content profiles. In the first meter of the soil profi le, 30 m of fiber optic cable were installed in a 12 loops coil. The metal sheath armoring the fiber cable was used as an electrical resistance heater to generate a heat pulse, and the soil response was monitored with a Distributed Temperature Sensing (DTS) system. We study the cooling following three continuous heat pulses of 120 s at 36 W m(-1) by means of long-time approximation of radial heat conduction. The soil volumetric water contents were then inferred from the estimated thermal conductivities through a specifically calibrated model relating thermal conductivity and volumetric water content. To use the pre-asymptotic data we employed a time correction that allowed the volumetric water content to be estimated with a precision of 0.01-0.035 (m(3) m(-3)). A comparison of the AHFO measurements with soil-moisture measurements obtained with calibrated capacitance-based probes gave good agreement for wetter soils [discrepancy between the two methods was less than 0.04 (m(3) m(-3))]. In the shallow drier soils, the AHFO method underestimated the volumetric water content due to the longertime required for the temperature increment to become asymptotic in less thermally conductive media [discrepancy between the two methods was larger than 0.1 (m(3) m(-3))]. The present work suggests that future applications of the AHFO method should include longer heat pulses, that longer heating and cooling events are analyzed, and, temperature increments ideally be measured with higher frequency.

Light-emitting diodes (LED) for domestic lighting: any risks for the eye?

Light-emitting diodes (LEDs) are taking an increasing place in the market of domestic lighting because they produce light with low energy consumption. In the EU, by 2016, no traditional incandescent light sources will be available and LEDs may become the major domestic light sources. Due to specific spectral and energetic characteristics of white LEDs as compared to other domestic light sources, some concerns have been raised regarding their safety for human health and particularly potential harmful risks for the eye. To conduct a health risk assessment on systems using LEDs, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), a public body reporting to the French Ministers for ecology, for health and for employment, has organized a task group. This group consisted physicists, lighting and metrology specialists, retinal biologist and ophthalmologist who have worked together for a year. Part of this work has comprised the evaluation of group risks of different white LEDs commercialized on the French market, according to the standards and found that some of these lights belonged to the group risk 1 or 2. This paper gives a comprehensive analysis of the potential risks of white LEDs, taking into account pre-clinical knowledge as well as epidemiologic studies and reports the French Agency's recommendations to avoid potential retinal hazards.

Fast quantification of ten psychotropic drugs and metabolites in human plasma by ultra-high performance liquid chromatography tandem mass spectrometry for therapeutic drug monitoring.

A sensitive and selective ultra-high performance liquid chromatography (UHPLC) tandem mass spectrometry (MS/MS) method was developed for the fast quantification of ten psychotropic drugs and metabolites in human plasma for the needs of our laboratory (amisulpride, asenapine, desmethyl-mirtazapine, iloperidone, mirtazapine, norquetiapine, olanzapine, paliperidone, quetiapine and risperidone). Stable isotope-labeled internal standards were used for all analytes, to compensate for the global method variability, including extraction and ionization variations. Sample preparation was performed by generic protein precipitation with acetonitrile. Chromatographic separation was achieved in less than 3.0min on an Acquity UPLC BEH Shield RP18 column (2.1mm×50mm; 1.7μm), using a gradient elution of 10mM ammonium formate buffer pH 3.0 and acetonitrile at a flow rate of 0.4ml/min. The compounds were quantified on a tandem quadrupole mass spectrometer operating in positive electrospray ionization mode, using multiple reaction monitoring. The method was fully validated according to the latest recommendations of international guidelines. Eight point calibration curves were used to cover a large concentration range 0.5-200ng/ml for asenapine, desmethyl-mirtazapine, iloperidone, mirtazapine, olanzapine, paliperidone and risperidone, and 1-1500ng/ml for amisulpride, norquetiapine and quetiapine. Good quantitative performances were achieved in terms of trueness (93.1-111.2%), repeatability (1.3-8.6%) and intermediate precision (1.8-11.5%). Internal standard-normalized matrix effects ranged between 95 and 105%, with a variability never exceeding 6%. The accuracy profiles (total error) were included in the acceptance limits of ±30% for biological samples. This method is therefore suitable for both therapeutic drug monitoring and pharmacokinetic studies.

New microfluidic-based sampling procedure for overcoming the hematocrit problem associated with dried blood spot analysis.

Hematocrit (Hct) is one of the most critical issues associated with the bioanalytical methods used for dried blood spot (DBS) sample analysis. Because Hct determines the viscosity of blood, it may affect the spreading of blood onto the filter paper. Hence, accurate quantitative data can only be obtained if the size of the paper filter extracted contains a fixed blood volume. We describe for the first time a microfluidic-based sampling procedure to enable accurate blood volume collection on commercially available DBS cards. The system allows the collection of a controlled volume of blood (e.g., 5 or 10 μL) within several seconds. Reproducibility of the sampling volume was examined in vivo on capillary blood by quantifying caffeine and paraxanthine on 5 different extracted DBS spots at two different time points and in vitro with a test compound, Mavoglurant, on 10 different spots at two Hct levels. Entire spots were extracted. In addition, the accuracy and precision (n = 3) data for the Mavoglurant quantitation in blood with Hct levels between 26% and 62% were evaluated. The interspot precision data were below 9.0%, which was equivalent to that of a manually spotted volume with a pipet. No Hct effect was observed in the quantitative results obtained for Hct levels from 26% to 62%. These data indicate that our microfluidic-based sampling procedure is accurate and precise and that the analysis of Mavoglurant is not affected by the Hct values. This provides a simple procedure for DBS sampling with a fixed volume of capillary blood, which could eliminate the recurrent Hct issue linked to DBS sample analysis.

Radiometric age constraints on mineral growth, metamorphism, and tectonism of the Gummfluh klippe, Brianconnais domain of the Prealpes, Switzerland

A combined Ar-40/Ar-39, K/Ar, Rb/Sr and stable isotope study has been made of white micas from the Gummfluh klippe (Brianconnais domain of the Prealpes), Switzerland. The klippe consists mainly of Mesozoic to early Tertiary carbonate rocks metamorphosed from anchizonal to epizonal conditions. At the base of the klippe is a 10-50 m thick, ductilely deformed marble mylonite containing deformed authigenic quartz segregations. Stable isotope measurements of the coexisting calcite (deltaO-18SMOW=24.5) and quartz (deltaO-18SMOW=28.4) from the mylonite indicate relatively low temperatures (< 300-degreesC) during mylonitization. Analyses of white mica separates of varying size fractions from the mylonitic rocks by K/Ar and Rb/Sr techniques yield ages between 57 and 103 Ma. This variation is correlated with two parameters, the size of the mineral fraction, and the proportion of 2M1 (more phengitic) to 1M (more muscovitic) polytype in the sample. The K/Ar and Rb/Sr ages are generally younger in the smaller size fractions, which also containless 2M1 phengite. High precision Ar-40/Ar-39 age spectra from different size fractions of these micas record three distinct components, a small Hercynian component (ca. 200-300 Ma), a significant Eoalpine component (64-80 Ma) forming Ar-40/Ar-39 age plateaus, and a very minor Tertiary component (ca. 20-40 Ma). Characterization of the samples by SEM indicates the presence of two white mica populations, a coarser grained, deformed, detrital mica that probably corresponds to the 2M1 phengite and a finer grained neoformed 1M mica. Collectively these observations suggest that the Gummfluh samples contain a mixture of detrital phengites of Hercynian age together with neocrystallized muscovites grown during the late Eoalpine metamorphic event followed by minor argon loss during the Tertiary. The main geologic episode recorded in the Ar-40/Ar-39 age spectra of white micas in the mylonite is of Late Cretaceous/Early Tertiary age (64-80 Ma), representing the first reliable Eoalpine ages ever to be reported from the Prealpes. Contrary to tectonic models, the marble mylonite at the base of the Gummfluh klippe appears to be a Cretaceous thrust plane and not the thrust surface formed during transport of the klippe into its present position from the Penninic Alps during the Tertiary. The late Cretaceous thrust developed during marine sedimentation at a depth of 800 m below the seafloor at temperatures of approximately 280-degrees-C, facilitated by warm fluids along the tectonic discontinuity.

Determination of meropenem in plasma and filtrate-dialysate from patients under continuous veno-venous haemodiafiltration by SPE-LC.

Meropenem, a carbapenem antibiotic displaying a broad spectrum of antibacterial activity, is administered in Medical Intensive Care Unit to critically ill patients undergoing continuous veno-venous haemodiafiltration (CVVHDF). However, there are limited data available to substantial rational dosing decisions in this condition. In an attempt to refine our knowledge and propose a rationally designed dosage regimen, we have developed a HPLC method to determine meropenem after solid-phase extraction (SPE) of plasma and dialysate fluids obtained from patients under CVVHDF. The assay comprises the simultaneous measurement of meropenem's open-ring metabolite UK-1a, whose fate has never been studied in CVVHDF patients. The clean-up procedure involved a SPE on C18 cartridge. Matrix components were eliminated with phosphate buffer pH 7.4 followed by 15:85 MeOH-phosphate buffer pH 7.4. Meropenem and UK-1a were subsequently desorbed with MeOH. The eluates were evaporated under nitrogen at room temperature (RT) and reconstituted in phosphate buffer pH 7.4. Separation was performed at RT on a Nucleosil 100-5 microm C18 AB cartridge column (125 x 4 mm I.D.) equipped with a guard column (8 x 4 mm I.D.) with UV-DAD detection set at 208 nm. The mobile phase was 1 ml min(-1), using a step-wise gradient elution program: %MeOH/0.005 M tetrabutylammonium chloride pH 7.4; 10/90-50/50 in 27 min. Over the range of 5-100 microg ml(-1), the regression coefficient of the calibration curves (plasma and dialysate) were >0.998. The absolute extraction recoveries of meropenem and UK-1a in plasma and filtrate-dialysate were stable and ranged from 88-93 to 72-77% for meropenem, and from 95-104 to 75-82% for UK-1a. In plasma and filtrate-dialysate, respectively, the mean intra-assay precision was 4.1 and 2.6% for meropenem and 4.2 and 3.7% for UK-1a. The inter-assay variability was 2.8 and 3.6% for meropenem and 2.3 and 2.8% for UK-1a. The accuracy was satisfactory for both meropenem and UK-1a with deviation never exceeding 9.0% of the nominal concentrations. The stability of meropenem, studied in biological samples left at RT and at +4 degrees C, was satisfactory with < 5% degradation after 1.5 h in blood but reached 22% in filtrate-dialysate samples stored at RT for 8 h, precluding accurate measurements of meropenem excreted unchanged in the filtrate-dialysate left at RT during the CVVHDF procedure. The method reported here enables accurate measurements of meropenem in critically ill patients under CVVHDF, making dosage individualisation possible in such patients. The levels of the metabolite UK-1a encountered in this population of patients were higher than those observed in healthy volunteers but was similar to those observed in patients with renal impairment under hemodialysis.

A novel method for quantification of sulfolane (a metabolite of busulfan) in plasma by gas chromatography-tandem mass spectrometry.

The role of busulfan (Bu) metabolites in the adverse events seen during hematopoietic stem cell transplantation and in drug interactions is not explored. Lack of availability of established analytical methods limits our understanding in this area. The present work describes a novel gas chromatography-tandem mass spectrometric assay for the analysis of sulfolane (Su) in plasma of patients receiving high-dose Bu. Su and Bu were extracted from a single 100 μL plasma sample by liquid-liquid extraction. Bu was separately derivatized with 2,3,5,6-tetrafluorothiophenolfluorinated agent. Mass spectrometric detection of the analytes was performed in the selected reaction monitoring mode on a triple quadrupole instrument after electronic impact ionization. Bu and Su were analyzed with separate chromatographic programs, lasting 5 min each. The assay for Su was found to be linear in the concentration range of 20-400 ng/mL. The method has satisfactory sensitivity (lower limit of quantification, 20 ng/mL) and precision (relative standard deviation less than 15 %) for all the concentrations tested with a good trueness (100 ± 5 %). This method was applied to measure Su from pediatric patients with samples collected 4 h after dose 1 (n = 46), before dose 7 (n = 56), and after dose 9 (n = 54) infusions of Bu. Su (mean ± SD) was detectable in plasma of patients 4 h after dose 1, and higher levels were observed after dose 9 (249.9 ± 123.4 ng/mL). This method may be used in clinical studies investigating the role of Su on adverse events and drug interactions associated with Bu therapy.

Test result-based sampling: an efficient design for estimating the accuracy of patient safety indicators.

OBJECTIVE: Accuracy studies of Patient Safety Indicators (PSIs) are critical but limited by the large samples required due to low occurrence of most events. We tested a sampling design based on test results (verification-biased sampling [VBS]) that minimizes the number of subjects to be verified. METHODS: We considered 3 real PSIs, whose rates were calculated using 3 years of discharge data from a university hospital and a hypothetical screen of very rare events. Sample size estimates, based on the expected sensitivity and precision, were compared across 4 study designs: random and VBS, with and without constraints on the size of the population to be screened. RESULTS: Over sensitivities ranging from 0.3 to 0.7 and PSI prevalence levels ranging from 0.02 to 0.2, the optimal VBS strategy makes it possible to reduce sample size by up to 60% in comparison with simple random sampling. For PSI prevalence levels below 1%, the minimal sample size required was still over 5000. CONCLUSIONS: Verification-biased sampling permits substantial savings in the required sample size for PSI validation studies. However, sample sizes still need to be very large for many of the rarer PSIs.

Inferring recent migration rates from individual genotypes.

We present a novel and straightforward method for estimating recent migration rates between discrete populations using multilocus genotype data. The approach builds upon a two-step sampling design, where individual genotypes are sampled before and after dispersal. We develop a model that estimates all pairwise backwards migration rates (m(ij), the probability that an individual sampled in population i is a migrant from population j) between a set of populations. The method is validated with simulated data and compared with the methods of BayesAss and Structure. First, we use data for an island model and then we consider more realistic data simulations for a metapopulation of the greater white-toothed shrew (Crocidura russula). We show that the precision and bias of estimates primarily depend upon the proportion of individuals sampled in each population. Weak sampling designs may particularly affect the quality of the coverage provided by 95% highest posterior density intervals. We further show that it is relatively insensitive to the number of loci sampled and the overall strength of genetic structure. The method can easily be extended and makes fewer assumptions about the underlying demographic and genetic processes than currently available methods. It allows backwards migration rates to be estimated across a wide range of realistic conditions.

Constraining ACT-R models of decision strategies: An experimental paradigm

It has been repeatedly debated which strategies people rely on in inference. These debates have been difficult to resolve, partially because hypotheses about the decision processes assumed by these strategies have typically been formulated qualitatively, making it hard to test precise quantitative predictions about response times and other behavioral data. One way to increase the precision of strategies is to implement them in cognitive architectures such as ACT-R. Often, however, a given strategy can be implemented in several ways, with each implementation yielding different behavioral predictions. We present and report a study with an experimental paradigm that can help to identify the correct implementations of classic compensatory and non-compensatory strategies such as the take-the-best and tallying heuristics, and the weighted-linear model.

Sensitive bioassay for determination of fluconazole concentrations in plasma using a Candida albicans mutant hypersusceptible to azoles.

The antifungal agent fluconazole (FLC) is widely used in clinical practice. Monitoring FLC levels is useful in complicated clinical settings and in experimental infection models. A bioassay using Candida pseudotropicalis, a simple and cost-effective method, is validated only for FLC levels ranging from 5 to 40 mg/liter. An extension of the analytical range is needed to cover most yeast MICs. A new bioassay in RPMI agar containing methylene blue was developed using C. albicans DSY1024, a mutant rendered hypersusceptible to FLC constructed by the deletion of the multidrug efflux transporter genes CDR1, CDR2, CaMDR1, and FLU1. Reproducible standard curves were obtained with FLC concentrations in plasma ranging from 1 to 100 mg/liter (quadratic regression coefficient &gt; 0.997). The absolute sensitivity was 0.026 microg of FLC. The method was internally validated according to current guidelines for analytical method validation. Both accuracy and precision lied in the required +/-15% range. FLC levels measured by bioassay and by high-performance liquid chromatography (HPLC) performed with 62 plasma samples from humans and rats showed a strong correlation (coefficients, 0.979 and 0.995, respectively; percent deviations of bioassay from HPLC values, 0.44% +/- 15.31% and 2.66% +/- 7.54%, respectively). In summary, this newly developed bioassay is sensitive, simple, rapid, and inexpensive. It allows nonspecialized laboratories to determine FLC levels in plasma to within the clinically relevant concentration range and represents a useful tool for experimental treatment models.

Sensitive determination of D-lactic acid and L-lactic acid in urine by high-performance liquid chromatography-tandem mass spectrometry.

D-lactic acid in urine originates mainly from bacterial production in the intestinal tract. Increased D-lactate excretion as observed in patients affected by short bowel syndrome or necrotizing enterocolitis reflects D-lactic overproduction. Therefore, there is a need for a reliable and sensitive method able to detect D-lactic acid even at subclinical elevation levels. A new and highly sensitive method for the simultaneous determination of L- and D-lactic acid by a two-step procedure has been developed. This method is based on the concentration of lactic acid enantiomers from urine by supported liquid extraction followed by high-performance liquid chromatography-tandem mass spectrometry. The separation was achieved by the use of an Astec Chirobiotic? R chiral column under isocratic conditions. The calibration curves were linear over the ranges of 2-400 and 0.5-100 µmol/L respectively for L- and D-lactic acid. The limit of detection of D-lactic acid was 0.125 µmol/L and its limit of quantification was 0.5 µmol/L. The overall accuracy and precision were well within 10% of the nominal values. The developed method is suitable for production of reference values in children and could be applied for accurate routine analysis.