Genome-Wide Association Study of Acute Renal Graft Rejection.

Acute renal rejection is a major risk factor for chronic allograft dysfunction and long-term graft loss. We performed a genome-wide association study to detect loci associated with biopsy-proven acute T cell-mediated rejection occurring in the first year after renal transplantation. In a discovery cohort of 4127 European renal allograft recipients transplanted in eight European centers, we used a DNA pooling approach to compare 275 cases and 503 controls. In an independent replication cohort of 2765 patients transplanted in two European countries, we identified 313 cases and 531 controls, in whom we genotyped individually the most significant single nucleotide polymorphisms (SNPs) from the discovery cohort. In the discovery cohort, we found five candidate loci tagged by a number of contiguous SNPs (more than five) that was never reached in iterative in silico permutations of our experimental data. In the replication cohort, two loci remained significantly associated with acute rejection in both univariate and multivariate analysis. One locus encompasses PTPRO, coding for a receptor-type tyrosine kinase essential for B cell receptor signaling. The other locus involves ciliary gene CCDC67, in line with the emerging concept of a shared building design between the immune synapse and the primary cilium.

Operational tolerance in kidney transplantation and associated biomarkers.

In the 1960s, our predecessors won a historical battle against acute rejection and ensured that transplantation became a common life-saving treatment. In parallel with this success, or perhaps because of it, we lost the battle for long-lived transplants, being overwhelmed with chronic immune insults and the toxicities of immunosuppression. It is likely that current powerful treatments block acute rejection, but at the same time condemn the few circulating donor cells that would have been able to elicit immunoregulatory host responses towards the allograft. Under these conditions, spontaneously tolerant kidney recipients - i.e. patients who maintain allograft function in the absence of immunosuppression - are merely accidents; they are scarce, mysterious and precious. Several teams pursue the goal of finding a biomarker that would guide us towards the 'just right' level of immunosuppression that avoids rejection while leaving some space for donor immune cells. Some cellular assays are attractive because they are antigen-specific, and provide a comprehensive view of immune responses toward the graft. These seem to closely follow patient regulatory capacities. However, these tests are cumbersome, and require abundant cellular material from both donor and recipient. The latest newcomers, non-antigen-specific recipient blood transcriptomic biomarkers, offer the promise that a practicable and simple signature may be found that overcomes the complexity of a system in which an infinite number of individual cell combinations can lead possibly to graft acceptance. Biomarker studies are as much an objective - identifying tolerant patients, enabling tolerance trials - as a means to deciphering the underlying mechanisms of one of the most important current issues in transplantation.

[Professional fatigue syndrome (burnout). Part 1 : identification by the general practitioner]. / Syndrome de fatigue professionnelle (burnout) 1ère partie : de l'identification par le médecin généraliste.

Burnout or professional fatigue syndrome has never been more talked about than in recent times. It is the result of exposure to a situation in which the strategies of the subject who are supposed to manage the stresses of the environment become outdated and inoperative. An imbalance is created between the demands and the material, operational and psychological resources to cope with them. Many health professions are confronted with the challenge of managing burnout. Among them, the general practitioner is very often on the front line. This paper is dedicated to him in priority. In its first part, it deals successively with the classification of the pathology (ICD-10 and DSM-5), its prevalence, its socio-economic impacts, its clinical picture (three stages), its diagnosis (by clinic and questionnaires), its causes, its evolution (from denial to acceptance), and its long-term consequences in the absence of treatment.

Le burnout ou syndrome de fatigue professionnelle n'a jamais autant fait parler de lui que ces derniers temps. Il est le résultat de l'exposition à une situation durant laquelle les stratégies du sujet, qui sont censées gérer les stress de l'environnement, deviennent dépassées et inopérantes. Un déséquilibre se crée entre l'exigence des demandes et les ressources matérielles, opérationnelles et psychologiques pour y faire face. De nombreuses professions de santé se trouvent confrontées au défi de la prise en charge du burnout. Parmi celles-ci, le médecin généraliste est très souvent en première ligne. Cet article s'adresse à lui en priorité. Dans ce premier volet, il traite successivement de la classification de la pathologie (ICD-10 et DSM-5), de sa prévalence, de ses impacts socio-économiques, de son tableau clinique (trois stades), de son diagnostic (par la clinique et les questionnaires), de ses causes, de son évolution (du déni à l'acceptation) et de ses conséquences à long terme en l'absence de traitement.

[Professional fatigue syndrome (burnout) : Part 2 : from therapeutic management]. / Syndrome de fatigue professionnelle (burnout) 2ème partie : de la prise en charge thérapeutique.

Burnout or professional fatigue syndrome is the result of exposure to a situation in which the strategies of the subject who are supposed to manage the stresses of the environment become outdated and inoperative. An imbalance is created between the demands and the material, operational and psychological resources to cope with them. Many health professions are confronted with the challenge of managing burnout, but the general practitioner is very often on the front line. After a first article devoted to the epidemiology, diagnosis, causes and consequences of the burnout, this second article is focusing on its therapeutic management, through listening, sick leave, dietary supplements, antidepressants, behavioural and cognitive therapy, professional coaching and multidisciplinary approach.

on disponible Résumé : Le burnout ou syndrome de fatigue professionnelle est le résultat de l'exposition à une situation durant laquelle les stratégies du sujet, qui sont censées gérer les stress de l'environnement, deviennent dépassées et inopérantes. Un déséquilibre se crée entre l'exigence des demandes et les ressources matérielles, opérationnelles et psychologiques pour y faire face. De nombreuses professions de santé se trouvent confrontées au défi de la prise en charge du burnout, dont le médecin généraliste. Après un premier article dédié à l'épidémiologie, au diagnostic, aux causes et aux conséquences du burnout, ce second article est consacré à la prise en charge de ce syndrome. Il se centre sur la prise en charge thérapeutique par l'écoute, l'interruption du temps de travail, les compléments alimentaires, les antidépresseurs, la thérapie comportementale et cognitive, le coaching professionnel et l'approche multidisciplinaire.

Array comparative genomic hybridization in male infertility.

BACKGROUND: Male infertility caused by a maturation arrest of spermatogenesis is a condition with an abrupt stop in spermatogenesis, mostly at the level of primary spermatocytes. The etiology remains largely unknown. METHODS: We focused on patients with a complete arrest at the spermatocyte level (n = 9) and used array comparative genomic hybridization to screen for deletions or duplications that might be associated with maturation arrest. Interesting copy number variations (CNVs) were further examined by using quantitative PCR. Where appropriate, the expression pattern was analyzed in multiple human tissues including the testis. RESULTS: A total of 227 CNVs were detected in the patient group. After the elimination of CNVs that were also present in the control group or that were not likely to be involved in male infertility, the remaining 11 regions were investigated more in detail. We first determined the expression pattern of seven genes, for which expression had not been reported to be investigated in testicular tissue, after which one region could be eliminated. Next, all 10 promising candidate regions were analyzed by quantitative PCR in a control population. CONCLUSIONS: Eight deletions/duplications were absent in our control group, and therefore might be linked with the male infertility in our patients. One of these alterations, however, has been detected in a proven fertile father group. Further research is necessary to determine the relationship between the observed genomic alterations and maturation arrest of spermatogenesis. Furthermore, several of the above genes have not been studied at the functional level and consequently, more research is required to determine their role in spermatogenesis.

Lipid peroxidation in judoists using oral contraceptives.

12 female judoists using oral contraceptives (OCU) containing 0.03 mg ethinylestradiol and 3 mg drospirenone for 20 ± 12 months (mean ± SD) were compared with a control group of 14 judoist noncontraceptive users (NCU) in order to evaluate resting (T1) and postexercise (T2) lipid peroxidation (LPO) and antioxidant parameters. Data were collected 20 min before and 10 min after a morning session of judo training and included determination of lag phase (Lp) before free radical-induced oxidation, glutathione peroxidase (GPx), α-tocopherol, retinol, and oxidative stress markers related to LPO. Significantly higher resting oxidative stress (+125.8 and +165.2% for malondialdehyde and lipid peroxides, respectively) and lower values of Lp and GPx (-23.4 and -12.1%, respectively) were observed in the OCU compared with NCU. The judo training session induced an increase in plasma LPO whatever the treatment. We noted significant increases in Lp (+14.7%; p<0.05 vs. preexercise) and GPx (22.1%; p<0.05 vs. preexercise) only in the NCU group. We suggest that a judo training session favourably altered some antioxidants in NCU but not in OCU. As excessive oxidative stress is linked to the development of several chronic diseases, the use of agents to reduce antioxidants may be reasonable in OCU.

Gross efficiency and energy expenditure in kayak ergometer exercise.

We purposed to study energy expenditure, power output and gross efficiency during kayak ergometer exercise in 12 elite sprint kayakers. 6 males (age 24.2±4.8 years, height 180.4±4.8 cm, body mass 79.7±8.5 kg) and 6 females (age 24.3±4.5 years, height 164.5±3.9 cm, body mass 65.4±3.5 kg), performed an incremental intermittent protocol on kayak ergometer with VO2 and blood lactate concentration assessment, a non-linear increase between power output and energy expenditure being observed. Paddling power output, energy expenditure and gross efficiency corresponding to VO2max averaged 199.92±50.41 W, 75.27±6.30 ml.kg - 1.min - 1, and 10.10±1.08%. Male kayakers presented higher VO2max, power output and gross efficiency at the VO2max, and lower heart rate and maximal lactate concentration than females, but no differences were found between genders regarding energy expenditure at VO2max. Aerobic and anaerobic components of energy expenditure evidenced a significant contribution of anaerobic energy sources in sprint kayak performance. Results also suggested the dependence of the gross efficiency on the changes in the amount of the aerobic and anaerobic contributions, at heavy and severe intensities. The inter-individual variance of the relationship between energy expenditure and the corresponding paddling power output revealed a relevant tracking for females (FDγ=0.73±0.06), conversely to the male group (FDγ=0.27±0.08), supporting that some male kayakers are more skilled in some paddling intensities than others.

Effects of 6 weeks of n-3 fatty acids and antioxidant mixture on lipid peroxidation at rest and postexercise.

The purpose of this randomized study was to measure the influence of 6 weeks of LCPUFA (600 mg EPA and 400 mg DHA per day) supplementation alone or in association with 30 mg vitamin E, 60 mg vitamin C and 6 mg ß-carotene on resting and exercise-induced lipid peroxidation in judoists (n = 36). Blood samples were collected at rest before (T (1)) and after the supplementation period, in preexercise (T (2)) and postexercise (T (3)) conditions, for analysis of α-tocopherol, retinol, lag phase (Lp) before free radical-induced oxidation, maximum rate of oxidation (R (max)) during the propagating chain reaction, maximum amount of conjugated dienes (CD(max)) accumulated after the propagation phase, and nitric oxide, malondialdehyde and lipoperoxide (POOL) concentrations. Dietary data were collected using a 7-day diet record. There were no significant differences among treatment groups with respect to habitual intakes of energy from fat, carbohydrate, or protein. At T (1), there were no significant differences among treatment groups with respect to lipid peroxidation, lag phase, and levels of α-tocopherol or retinol. The consumption of an n-3 LC PUFA supplement increased oxidative stress at rest and did not attenuate the exercise-induced oxidative stress. The addition of antioxidants did not prevent the formation of oxidation products at rest. On the contrary, it seems that the combination of antioxidants added to the n-3 LCPUFA supplement led to a decrease in, CD(max), R (max), and POOL and MDA concentrations after a judo training session.

Salivary alpha-amylase, cortisol and chromogranin A responses to a lecture: impact of sex.

The aim of this study was to (1) examine the presence of stress on professors when they teach in front of 200 students and analyse objectively such stress using biomarkers such as salivary cortisol, chromogranin A (CgA) and alpha-amylase (AA) (2) investigate whether sex affects the reactivity of salivary alpha-amylase (sAA) and cortisol concentrations and the interaction of both hormonal systems. Fifty-two participants (26 women and 26 men) collected nine unstimulated saliva samples on 2 days, (one working day, and one resting day). Cortisol concentrations and AA activity measured on the teaching day were significantly higher than those noted on the resting values. No differences between the resting day and the teaching day were reported for CgA. Our results showed a cortisol response to teaching, which was characterized by an anticipatory rise. The AA level was significantly increased after the end of the lecture, and returned to the pre-lecture level 30 min after the end of the lecture. The awakening cortisol response noted on the teaching day was significantly higher in females than in males. No baseline sex differences in sAA and CgA were observed and men and women seem to have a comparable reactivity in sAA, CgA and cortisol levels on lecture stress. The mechanisms that leads to modify activity of salivary AA and CgA due to stress is not entirely understood and further research is needed to elucidate them.

An unusual case of haemolytic uraemic syndrome following endoscopic retrograde cholangiopancreatography rapidly improved with eculizumab.

Atypical haemolytic uraemic syndrome (aHUS) is a rare but life-threatening complement system-related disorder, characterized by renal failure, non-immune haemolytic anaemia and thrombo-cytopenia. We report on a young woman who developed a pancreatitis-induced aHUS following a routine procedure of endoscopic retrograde cholangiopancreatography. The patient was successively treated by 2 plasma exchanges with fresh frozen plasma and eculizumab, a monoclonal antibody designed to block terminal complement activation. The last treatment resulted in the immediate improvement of haemolytic parameters and to the definitive suspension of plasma exchanges. This is likely the first description of the use of a complement inhibitor to treat post-pancreatitis aHUS. We discussed treatment options and concluded that eculizumab could be a beneficial alternative to plasma exchanges in the management of such complications.

A new HLA allocation procedure of kidneys from deceased donors in the current era of immunosuppression.

INTRODUCTION: It has recently been proposed to replace the current Eurotransplant kidney allocation based primarily on mismatches (MM) at the 3 HLA loci by a simpler system based on full HLA-DR compatibility. The present study analyzes this system in the current era of immunosuppression. METHODS: From 1999 to 2012, 723 renal grafts were performed on 586 patients who were treated with a calcineurin inhibitor, mycophenolate mofetil, and in most cases antilymphocyte globulins. Four groups of HLA MM were compared: (A) A+B 2-4/DR 1-2 MM (n = 397), (B) A+B 2-4 MM/DR 0 MM (n = 106), (C) A+B 0-1 MM/DR 1-2 MM (n = 138), and (D) A+B 0-1/DR 0 MM (n = 82). RESULTS: Acute rejection episodes were less frequent during the first post-transplantation year in group D than in the other groups (P = .018). Patient survival was lower in group A than in the other groups (P = .008). Immunologic graft survival was higher in group D than in the other groups in univariate (P = .015) and multivariate analyses (P = .033; 96.4% vs 90.1% at 10 years). CONCLUSIONS: In the current era of immunosuppression, allocation of kidneys from deceased donors could be performed primarily according to full DR compatibility then to the best A+B matching, affording excellent graft outcome to most recipients.

Patient and graft outcome in current era of immunosuppression: a single centre pilot study.

OBJECTIVES: The present single centre study aims at analyzing the impact on renal allograft outcome of the important changes which occurred in the transplant population and immunosuppressive therapy during the last two decades. METHODS: From 2000 to 2013, 779 single kidney transplantations were performed on 635 patients who all received on an intent-to-treat basis steroids, a calcineurin inhibitor, mycophenolate mofetil and an induction therapy with either antithymocyte globulin or an antagonist directed to the interleukin (IL)-2 receptor. Uni- and multivariate analyses of patient and immunologic graft survival were conducted. RESULTS: The sole factor predicting patient survival is recipient's age: 10-year survival rates are 94·7, 81·6 and 57·9% for the <45, 45-60 and >60 years age groups, respectively (P<0·001). Peak (>50% panel reactive antibodies) anti-human leucocyte antigens (HLA) sensitization, cold ischaemia time and HLA-B and -DR mismatches (MM) influence graft outcome: at 10 years, the difference in 10-year survival rates is 5·9% between grafts from sensitized and not sensitized patients (90·9 vs 96·8%, P = 0·002), 3·8% between grafts with <18 and ≧18 hours cold ischaemia (96·6 vs 92·8%, P = 0·003), 7·3% between grafts with no MM and either B or DR MM versus those with B and DR MM (96·8 vs 89·5%, P = 0·002). CONCLUSION: In our single centre experience, graft survival was most strongly determined by HLA matching, offering excellent long term graft outcome to most patients.

Survey of commercial pasteurised cows' milk in Wallonia (Belgium) for the occurrence of polychlorinated dibenzo-p-dioxins, dibenzofurans and coplanar polychlorinated biphenyls.

Congener-specific analyses of 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs) and 4 non-ortho (coplanar) polychlorinated biphenyls (cPCBs) were performed on 35 samples of commercial long-life pasteurised cows' milk issued from eight different brands available in Walloon supermarkets (Belgium). The observed congener profile was characteristic of milk samples issued from industrialised countries with good inter and intra-brand reproducibility's. The PCDDs to PCDFs ratio was equal to 1.8 in concentration. The toxic equivalent (TEQ based on WHO-TEF) value for PCDD/Fs in all analysed milks was 1.09+/-0.30 pg TEQ/g fat (range 0.86-1.59), which is below the recommended EU non-commercialisation threshold value of 3 pg TEQ PCDD/Fs/g of milk fat. The mean TEQ value including cPCBs was 2.23+/-0.55 pg TEQ/g fat. These PCBs actually contributed for 49+/-8.6% of the total TEQ. Among PCDD/Fs and cPCBs, tetrachloro dibenzo-p-dioxin (TCDD), pentachloro dibenzo-p-dioxin (PeCDD), pentachloro dibenzofurans (PeCDFs) and 3,3',4,4',5-pentachloro biphenyl (PCB-126) were the most important contributors to the TEQ. Estimated daily intake (EDI) due to consumption of such milks was 0.34 pg TEQ/kg of body weight/day for PCDD/Fs and 0.69 pg TEQ/kg of body weight/day when cPCBs were included.

Levels and congener distributions of PCDDs, PCDFs and non-ortho PCBs in Belgian foodstuffs--assessment of dietary intake.

Congener-specific analyses of 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs) and 4 non-ortho (coplanar) polychlorinated biphenyls (cPCBs) were performed on 197 foodstuffs samples of animal origin from Belgium during years 2000 and 2001. All investigated matrices (except horse) present background levels lower than the Belgian non-commercialization value of 5 pg TEQ/g fat. Pork was the meat containing the lowest concentration of both PCDD/Fs and cPCBs. The mean background concentration of 2,3,7,8-TCDD toxicity equivalent in milk was 1.1 pg/g of fat, with a congener distribution typical of non-contaminated milk. The relative contribution of 2,3,7,8-TCDD, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF to the PCDD/Fs TEQ was 85+/-7.9% for all investigated matrices. The cPCBs contribution to the total TEQ was 47+/-19.0% for products of terrestrial species and 69+/-20.0% for aquatic species. Once the contribution of cPCBs was added to the TEQ, few foodstuffs such as horse, sheep, beef, eggs and cheese presented levels above the future European guidelines that currently only include PCDD/Fs but will be re-evaluated later in order to include 'dioxin-like' PCBs. Based on levels measured in the samples, the estimation of the dietary intake was 65.3 pg WHO-TEQ/day for PCDD/Fs only (1.00 pg WHO-TEQ/kg bw/day, for a 65 kg person) and 132.9 pg WHO-TEQ/day if cPCBs were included (2.04 pg WHO-TEQ/kg bw/day, for a 65 kg person). Meat (mainly beef), dairy products, and fish each account for roughly one third of the intake.

Complement factor H functional assay may help to monitor atypical haemolytic uraemic syndrome: a pilot study.

BACKGROUND: Atypical haemolytic uraemic syndrome (aHUS) results from uncontrolled complement system activation. Complement factor H gene mutations are common causes of aHUS. Plasmatherapy, including plasma infusions and/or plasma exchanges, has been tried in this setting with various successes. At present, we lack a specific marker to monitor functional factor H deficiency-related aHUS. METHODS: We report the use of factor H functional assay in three patients with atypical haemolytic uraemic syndrome. This assay is based on the requirement of soluble complement regulators that bind sheep red cells to prevent haemolysis. As factor H is highly abundant in the plasma, its defect results in haemolysis. Factor H activity was also measured among plasma donors. RESULTS: One patient suffered from a plasma-dependent form of atypical haemolytic uraemic syndrome. Plasma exchanges restored higher factor H activity and were associated with a 15-months disease-free period. In the two other patients, one with a failing renal graft and the other on chronic dialysis, a bout of thrombotic microangiopathy was preceded by a drop of haemolytic activity below normal values. Plasma from healthy donors (N=65) showed only minimal variations of Factor H activity (mean activity: 98.3%, SD=4.0). CONCLUSION: These preliminary data suggest that factor H activity could be of interest in both the diagnosis and the treatment by plasmatherapy of factor H-related aHUS.

Differences in plasma cytokine levels between elite kayakers and nonathletes.

Regular moderate exercise has been shown to have anti-inflammatory effects that help prevent several chronic diseases. However, the effects of chronic training an elite athletes have not been the focus of much research. This study aimed to determine whether there were differences in cytokine levels (IL-1 ß , IL-1ra, IL-6, IL-10, IL-18, IFN- γ , and TNF- α ) in circulating peripheral blood (PB) between elite kayakers and nonathletes. Subjects were 13 elite male kayakers, aged 20.0 ± 3 years, with average body mass of 75.0 ± 7.9 kg and 177.3 ± 7.1 cm height and with a VO2max of 58.3 ± 7.8 mL·kg(-1)·min(-1). The nonathletes were 7 men, aged 18.2 ± 1.1 years, body mass of 81.3 ± 13.8 kg, and 171.9 ± 4.5 cm height. Blood samples were collected after six weeks of offtraining and before the start of a new training season. PB leukocyte populations were determined by flow cytometry. Cytokine levels were quantified by ELISA. When nonathletes were compared with the kayakers, the latter exhibited lower plasma concentrations of IL-1 ß , IL-18, and IFN- γ as well as a lower concentration of IL-1ra. Positive correlations between IL-18 and B cells in the athletes were also found. These results seem to reinforce the anti-inflammatory role of regular training.

Novel post-digest isotope coded protein labeling method for phospho- and glycoproteome analysis.

In the field of proteomics there is an apparent lack of reliable methodology for quantification of posttranslational modifications. Present study offers a novel post-digest ICPL quantification strategy directed towards characterization of phosphorylated and glycosylated proteins. The value of the method is demonstrated based on the comparison of two prostate related metastatic cell lines originating from two distinct metastasis sites (PC3 and LNCaP). The method consists of protein digestion, ICPL labeling, mixing of the samples, PTM enrichment and MS-analysis. Phosphorylated peptides were isolated using TiO(2), whereas the enrichment of glycosylated peptides was performed using hydrazide based chemistry. Isolated PTM peptides were analyzed along with non enriched sample using 2D-(SCX-RP)-Nano-HPLC-MS/MS instrumentation. Taken together the novel ICPL labeling method offered a significant improvement of the number of identified (∼600 individual proteins) and quantified proteins (>95%) in comparison to the classical ICPL method. The results were validated using alternative protein quantification strategies as well as label-free MS quantification method. On the biological level, the comparison of PC3 and LNCaP cells has shown specific modulation of proteins implicated in the fundamental process related to metastasis dissemination. Finally, a preliminary study involving clinically relevant autopsy cases reiterated the potential biological value of the discovered proteins.

Quantitative buffy coat analysis related to adrenocortical function in horses during a three-day event competition.

This study was carried out to investigate stress induced in a cross-country by measuring plasma cortisol and to compare the changes in cortisol level with the leucocytic changes measured with the quantitative buffy coat (QBC) analysis, which is a new method applicable in field conditions for the evaluation of haematological parameters in horses. Seven healthy horses competing in a national three-day event were investigated. Venous blood was sampled under resting condition, 2 min and 180 min after the completion of the cross-country and analysed for haematological parameters, plasma cortisol, protein and lactate levels. Immediately after the event, there was a significant increase in all values except in the granulocytes (Gr) to lymphocytes-monocytes (LM) ratio. 180 min after the event, all the parameters returned to their resting levels while white blood cells (WBC), Gr and Gr/LM ratio were significantly higher with respect to their resting values. A high correlation (r = 0.82) was found between the relative increase in plasma cortisol levels 2 min after exercise and the relative increase in Gr/LM 180 min after exercise. Therefore it was concluded that the Gr/LM ratio measured 180 min after exercise with the QBC analysis is a reliable index to estimate the plasma cortisol levels measured 2 min after exercise. This new technique could consequently be used in order to evaluate, in field conditions, the exercise-induced stress.

Validation of the CALUX bioassay for PCDD/F analyses in human blood plasma and comparison with GC-HRMS.

Following the dioxin crisis of 1999, several studies were conducted to assess the impact of this crisis on the dioxin body burden in the Belgian population. The Scientific Institute of Public Health identified a population from whom plasma samples were available and from whom, during the follow up survey, plasma samples were obtained in 2000. In total, 496 samples were collected for GC-HRMS and CALUX analyses to verify statistical assessment conclusions. This study was seen as an opportunity to validate the CALUX bioassay for biological sample analysis and to compare toxic equivalency (TEQ) values obtained by the reference GC-HRMS technique and by the screening method. This article focuses on the validation results of the CALUX bioassay for the analyses of the dioxin fractions of blood plasma. The sample preparation is based on a liquid-liquid extraction, followed by an acid silica in series with an activated carbon clean-up. A good recovery (82%) and reproducibility (coefficient of variation less than 25%) were found for this method. Based on 341 plasma samples, a significant correlation was established between the bioassay and chemical method (R = 0.64). However, a proportional systematic error was observed when the results obtained with the CALUX bioassay were regressed with the results from the GC-HRMS analyses. The limit of quantification (LOQ) used to calculate TEQ values from the GC-HRMS determinations, the use of the relative potency values instead of the toxic equivalent factor and the potential of CALUX bioassay to measure all compounds with affinity for the AhR may partly explain this proportional systematic error. Nevertheless, the present results suggest that the CALUX bioassay could be a promising valid screening method for human blood plasma analyses.