Vrednovanje analitičkih metoda i laboratorijskih postupaka u kemijskim mjerenjima

Method validation is a key element in the establishment of reference methods and in the assessment of a laboratory’s competence in producing reliable analytical data. Hence, the scope of the term »method validation« is wide, especially if one bears in mind the role of Quality Assurance/Quality Control (QA/QC). The paper puts validation in the context of the process generating chemical information, introduces basic performance parameters included in the validation processes, and evaluates current approaches to the problem. Two cases are presented in more detail: the development of European standard for chlorophenols and its validation by a full scale collaborative trial and the intralaboratory validation of a method for ethylenethiourea (ETU) by using alternative analytical techniques.Vrednovanje metoda ključni je postupak u utvrđivanju referentnih metoda i procjeni kompetencije laboratorija da proizvodi pouzdane rezultate analiza. Stoga je značenje širine okvira ovog termina posebice važno jer valja imati na umu i ulogu osiguranja kakvoće i kontrole kakvoće. Autori stavljaju postupak vrednovanja metoda u kontekst proizvodnje kemijskoanalitičkih podataka, upoznaju čitatelja s osnovnim parametrima pri ocjeni uspješnosti te ocjenjuju trenutne pristupe ovom problemu. U dva je primjera posebna pozornost posvećena razvoju europske norme za klorofenole i njezinoj ocjeni opsežnim pokusom te unutarlaboratorijskom potvrdom metode za određivanje etilentioureje rabeći alternativne analitičke tehnike

The use of the DR CALUX bioassay and indicator polychlorinated biphenyls for screening of elevated levels of dioxins and dioxin-like polychlorinated biphenyls in eel.

The DR CALUX bioassay is a very suitable screening method for dioxins and dioxin-like-PCBs in feed and food. This was, e. g. demonstrated in a survey in the Netherlands to control the dioxin levels in eel. The DR CALUX assay, but also indicator polychlorinated biphenyls (PCB) were evaluated as a screening method. Based on the limit for polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/F) [at that time 8 pg toxic equivalents (TEQ)/g eel], and the relation between PCDD/F and dioxin-like-PCB, a decision limit of 30 pg TEQ/g eel was used for screening of 153 field samples. Suspected samples (21) and part of the higher contaminated negative samples (35) were analyzed by GC/MS for dioxins, non-ortho, mono-ortho and indicator PCB, revealing 13 samples exceeding the action limit of 30 pg TEQ/g eel. Only one sample slightly exceeded the dioxin level of 8 pg TEQ/g eel. The relatively low sensitivity for mono-ortho PCB was overcome by the use of reference samples, as shown by the correlation of 0.93 between GC/MS and CALUX determined total TEQ levels. The present data show that the DR CALUX assay can be used for screening of total TEQ levels in eel. The use for dioxins only requires a safe, and therefore relatively low, decision limit. The indicator PCB also showed a good correlation with total TEQ levels, mainly due to the large contribution of the mono-ortho PCB at higher concentrations. The relation with dioxins was very poor and as such indicator PCB seem less suitable than the DR CALUX assay for screening for dioxins only. The present study clearly shows that part of the wild eel samples contains high total TEQ levels and will exceed the future European Union limit of 12 pg TEQ/g eel for dioxins and dioxin-like PCB. Especially at high TEQ levels, dioxin-like PCB contribute most to the total TEQ. In practice, wild eel presents only a minor part of the eel consumed

Vrednovanje analitičkih metoda i laboratorijskih postupaka u kemijskim mjerenjima

Method validation is a key element in the establishment of reference methods and in the assessment of a laboratory’s competence in producing reliable analytical data. Hence, the scope of the term »method validation« is wide, especially if one bears in mind the role of Quality Assurance/Quality Control (QA/QC). The paper puts validation in the context of the process generating chemical information, introduces basic performance parameters included in the validation processes, and evaluates current approaches to the problem. Two cases are presented in more detail: the development of European standard for chlorophenols and its validation by a full scale collaborative trial and the intralaboratory validation of a method for ethylenethiourea (ETU) by using alternative analytical techniques.Vrednovanje metoda ključni je postupak u utvrđivanju referentnih metoda i procjeni kompetencije laboratorija da proizvodi pouzdane rezultate analiza. Stoga je značenje širine okvira ovog termina posebice važno jer valja imati na umu i ulogu osiguranja kakvoće i kontrole kakvoće. Autori stavljaju postupak vrednovanja metoda u kontekst proizvodnje kemijskoanalitičkih podataka, upoznaju čitatelja s osnovnim parametrima pri ocjeni uspješnosti te ocjenjuju trenutne pristupe ovom problemu. U dva je primjera posebna pozornost posvećena razvoju europske norme za klorofenole i njezinoj ocjeni opsežnim pokusom te unutarlaboratorijskom potvrdom metode za određivanje etilentioureje rabeći alternativne analitičke tehnike

Stable isotope tagging of epitopes: a highly selective strategy for the identification of major histocompatibility complex class I-associated peptides induced upon viral infection.

Identification of peptides presented in major histocompatibility complex (MHC) class I molecules after viral infection is of strategic importance for vaccine development. Until recently, mass spectrometric identification of virus-induced peptides was based on comparative analysis of peptide pools isolated from uninfected and virus-infected cells. Here we report on a powerful strategy aiming at the rapid, unambiguous identification of naturally processed MHC class I-associated peptides, which are induced by viral infection. The methodology, stable isotope tagging of epitopes (SITE), is based on metabolic labeling of endogenously synthesized proteins during infection. This is accomplished by culturing virus-infected cells with stable isotope-labeled amino acids that are expected to be anchor residues (i.e. residues of the peptide that have amino acid side chains that bind into pockets lining the peptide-binding groove of the MHC class I molecule) for the human leukocyte antigen allele of interest. Subsequently these cells are mixed with an equal number of non-infected cells, which are cultured in normal medium. Finally peptides are acid-eluted from immunoprecipitated MHC molecules and subjected to two-dimensional nanoscale LC-MS analysis. Virus-induced peptides are identified through computer-assisted detection of characteristic, binomially distributed ratios of labeled and unlabeled molecules. Using this approach we identified novel measles virus and respiratory syncytial virus epitopes as well as infection-induced self-peptides in several cell types, showing that SITE is a unique and versatile method for unequivocal identification of disease-related MHC class I epitopes

Evaluation of a patient decision aid for BRCA1/2 pathogenic variant carriers choosing an ovarian cancer prevention strategy

OBJECTIVE: Risk-reducing surgery is advised to BRCA1/2 pathogenic variant (PV) carriers around the age of 40 years to reduce ovarian cancer risk. In the TUBA-study, a multicenter preference study (NCT02321228), BRCA1/2-PV carriers are offered a choice: the standard strategy of risk-reducing salpingo-oophorectomy or the novel strategy of risk-reducing salpingectomy with delayed oophorectomy. We evaluated feasibility and effectiveness of a patient decision aid for this choice. METHODS: Premenopausal BRCA1/2-PV carriers were counselled for risk-reducing surgical options in the TUBA-study; the first cohort was counselled without and the second cohort with decision aid. Evaluation was performed using digital questionnaires for participating women and their healthcare professionals. Outcome measures included actual choice, feasibility (usage and experiences) and effectiveness (knowledge, cancer worry, decisional conflict, decisional regret and self-estimated influence on decision). RESULTS: 283 women were counselled without and 282 women with decision aid. The novel strategy was chosen less frequently in women without compared with women with decision aid (67% vs 78%, p = 0.004). The decision aid was graded with an 8 out of 10 by both women and professionals, and 78% of the women would recommend this decision aid to others. Users of the decision aid reported increased knowledge about the options and increased insight in personal values. Knowledge on cancer risk, decisional conflict, decisional regret and cancer worry were similar in both cohorts. CONCLUSIONS: The use of the patient decision aid for risk-reducing surgery is feasible, effective and highly appreciated among BRCA1/2-PV carriers facing the decision between salpingo-oophorectomy or salpingectomy with delayed oophorectomy

Results of the first European Source Apportionment intercomparison for Receptor and Chemical Transport Models

In this study, the performance of the source apportionment model applications were evaluated by comparing the model results provided by 44 participants adopting a methodology based on performance indicators: z-scores and RMSEu, with pre-established acceptability criteria. Involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), provided a unique opportunity to cross-validate them. In addition, comparing the modelled source chemical profiles, with those measured directly at the source contributed to corroborate the chemical profile of the tested model results. The most used RM was EPA- PMF5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) and more difficulties are observed with SCE time series (72% of RMSEu accepted). Industry resulted the most problematic source for RMs due to the high variability among participants. Also the results obtained with CTMs were quite comparable to their ensemble reference using all models for the overall average (>92% of successful z-scores) while the comparability of the time series is more problematic (between 58% and 77% of the candidates’ RMSEu are accepted). In the CTM models a gap was observed between the sum of source contributions and the gravimetric PM10 mass likely due to PM underestimation in the base case. Interestingly, when only the tagged species CTM results were used in the reference, the differences between the two CTM approaches (brute force and tagged species) were evident. In this case the percentage of candidates passing the z-score and RMSEu tests were only 50% and 86%, respectively. CTMs showed good comparability with RMs for the overall dataset (83% of the z-scores accepted), more differences were observed when dealing with the time series of the single source categories. In this case the share of successful RMSEu was in the range 25% - 34%.JRC.C.5-Air and Climat

Screening suspected counterfeit Viagra and imitations of Viagra with near-infrared spectroscopy.

We describe a near-infrared spectroscopy (NIRS) method for fast-screening Viagra tablets, counterfeit Viagra tablets, and imitations of Viagra. The method can (1) check the homogeneity of a batch; (2) distinguish counterfeits and imitations from authentic Viagra; (3) screen for the presence of sildenafil citrate, the pharmacologically active substance in Viagra, irrespectively of the excipients present; (4) and detect whether similar samples have been previously analysed. We applied the method to 103 samples with a diversity of appearance, chemical composition, and origin. Other analytical methods confirmed the positive screening results for sildenafil citrate and the presence of other pharmacological active substances. The NIRS screening indicated the absence of sildenafil citrate in the presence of another pharmacological substance for only 2 samples, where the reference methods showed the presence of sildenafil citrate in addition to that of clomifene citrate. Otherwise, the method gave no false positive or negative results. The NIRS screening method is very fast and reliable for detecting counterfeits and imitations, and it correctly predicts the presence or absence of sildenafil citrate in 98% of the samples

Particulate air pollution from different sources and mortality in 7.5 million adults — The Dutch Environmental Longitudinal Study (DUELS)

Background: Long-term exposure to particulate air pollution has been associated with mortality in urban cohort studies. Few studies have investigated the association between emission contributions from different particle sources and mortality in large-scale population registries, including non-urban populations. Objectives: The aim of the study was to evaluate the associations between long-term exposure to particulate air pollution from different source categories and non-accidental mortality in the Netherlands based on existing national databases. Methods: We used existing Dutch national databases on mortality, individual characteristics, residence history, neighbourhood characteristics and modelled air pollution concentrations from different sources and air pollution components: particulate matter PM10, primary particulate matter PM10 (PPM10), particulate matter PM2.5, primary particulate matter PM2.5 (PPM2.5), elemental carbon (EC), nitrogen dioxide (NO2) and secondary inorganic aerosol (SIA) in PM10 (SIA10) or in PM2.5 (SIA2.5). We established a cohort of 7.5 million individuals 30 years or older. We followed the cohort for eight years (2008–2015). We applied Cox proportional hazard regression models adjusting for potential individual and area-specific confounders. Results: We found statistically significant associations between total and primary particulate matter (PM10 and PM2.5), elemental carbon and mortality. Adjustment for nitrogen dioxide did not change the associations. Secondary inorganic aerosol showed less consistent associations. All primary PM sources were associated with mortality, except agricultural emissions and, depending on the statistical model, industrial PM emissions. Conclusions: We could not identify one or more specific source categories of particulate air pollution as main determinants of the mortality effects found in this and in a previous study. This suggests that present policy measures should be focussed on the wider spectrum of air pollution sources instead of on specific sources

Particulate air pollution from different sources and mortality in 7.5 million adults - The Dutch Environmental Longitudinal Study (DUELS).

We used existing Dutch national databases on mortality, individual characteristics, residence history, neighbourhood characteristics and modelled air pollution concentrations from different sources and air pollution components: particulate matter PM10, primary particulate matter PM10 (PPM10), particulate matter PM2.5, primary particulate matter PM2.5 (PPM2.5), elemental carbon (EC), nitrogen dioxide (NO2) and secondary inorganic aerosol (SIA) in PM10 (SIA10) or in PM2.5 (SIA2.5). We established a cohort of 7.5 million individuals 30 years or older. We followed the cohort for eight years (2008-2015). We applied Cox proportional hazard regression models adjusting for potential individual and area-specific confounders