Effect of a high dose of simvastatin on muscle mitochondrial metabolism and calcium signaling in healthy volunteers.

Statin use may be limited by muscle side effects. Although incompletely understood to date, their pathophysiology may involve oxidative stress and impairments of mitochondrial function and of muscle Ca(2+) homeostasis. In order to simultaneously assess these mechanisms, 24 male healthy volunteers were randomized to receive either simvastatin for 80 mg daily or placebo for 8 weeks. Blood and urine samples and a stress test were performed at baseline and at follow-up, and mitochondrial respiration and Ca(2+) spark properties were evaluated on a muscle biopsy 4 days before the second stress test. Simvastatin-treated subjects were separated according to their median creatine kinase (CK) increase. Simvastatin treatment induced a significant elevation of aspartate amino transferase (3.38±5.68 vs -1.15±4.32 UI/L, P<0.001) and CK (-24.3±99.1±189.3 vs 48.3 UI/L, P=0.01) and a trend to an elevation of isoprostanes (193±408 vs 12±53 pmol/mmol creatinine, P=0.09) with no global change in mitochondrial respiration, lactate/pyruvate ratio or Ca(2+) sparks. However, among statin-treated subjects, those with the highest CK increase displayed a significantly lower Vmax rotenone succinate and an increase in Ca(2+) spark amplitude vs both subjects with the lowest CK increase and placebo-treated subjects. Moreover, Ca(2+) spark amplitude was positively correlated with treatment-induced CK increase in the whole group (r=0.71, P=0.0045). In conclusion, this study further supports that statin induced muscular toxicity may be related to alterations in mitochondrial respiration and muscle calcium homeostasis independently of underlying disease or concomitant medication.

Regulation of oxidative stress by glycaemic control: evidence for an independent inhibitory effect of insulin therapy.

AIMS/HYPOTHESIS: We examined whether type of diabetes and/or insulin treatment can modulate the impact of sustained hyperglycaemia and glycaemic variability as activators of oxidative stress. METHODS: This was an observational study in 139 patients with diabetes, 48 with type 1, 60 with type 2 treated by oral hypoglycaemic agents (OHAs) alone and 31 with type 2 treated with insulin plus OHAs. In addition, two groups of ten patients with type 2 diabetes were investigated either before and after introducing insulin treatment (add-on insulin group) or before and after add-on OHA therapy to metformin (add-on OHA group). Oxidative stress was estimated from 24 h urinary excretion rates of 8-isoprostaglandin F2alpha (8-iso-PGF2alpha). HbA(1c) was assessed and mean amplitude of glycaemic excursions (MAGE) was estimated by continuous monitoring. RESULTS: The 24 h excretion rate of 8-iso-PGF2alpha (median [range] picomoles per millimole of creatinine) was much higher (p < 0.0001) in type 2 diabetes patients treated with OHAs alone (112 [26-329]) than in the type 1 diabetes group (65 [29-193]) and the type 2 diabetes group treated with insulin (69 [30-198]). It was associated with HbA(1c) (F = 12.9, p = 0.0008) and MAGE (F = 7.7, p = 0.008) in non-insulin-treated, but not in insulin-treated patients. A significant reduction in 24 h excretion rate of 8-iso-PGF2alpha from 126 (47-248) to 62 (35-111] pmol/mmol of creatinine was observed in the add-on insulin group (p = 0.005) but not in the add-on OHA group. CONCLUSIONS/INTERPRETATION: In type 1 and type 2 diabetes, insulin exerts an inhibitory effect on oxidative stress, a metabolic disorder that is significantly activated by sustained hyperglycaemia and glucose variability in non-insulin-treated type 2 diabetes.

An SOD rich melon extract Extramel prevents aortic lipids and liver steatosis in diet-induced model of atherosclerosis.

BACKGROUND AND AIMS: Oxidative stress has been involved in the early steps of atherosclerosis and previous studies on hypercholesterolemic hamsters have shown that non-enzymatic antioxidant could prevent fatty streak formation. Therefore, we investigated whether a melon juice extract (Extramel((R))) rich in superoxide dismutase (SOD) would prevent the development of early atherosclerosis. METHODS AND RESULTS: The effects of Extramel((R)) on plasma cholesterol, aortic fatty streak formation, hepatic steatosis, superoxide anion tissue production and NAD(P)H oxidase expression were studied in hamsters fed with an atherogenic diet (HF), receiving by gavage either water or Extramel((R)) at 0.7, 2.8 or 5.6mg/d. After 12 weeks of oral administration, Extramel((R)) lowered plasma cholesterol and non-HDL cholesterol and induced blood and liver SOD activities. It also strongly reduced the area of aortic fatty streak by 49-85%, cardiac (45%) and liver (67%) production of superoxide anion and liver p22(phox) subunit of NAD(P)H oxidase expression by 66%, and attenuated the development of hepatic steatosis. CONCLUSION: These findings support the view that chronic consumption of melon juice extract rich in SOD has potential beneficial effects with respect to the development of atherosclerosis and liver steatosis, emphasizing its use as potential dietary therapy.

Evolution of coronary artery calcifications following kidney transplantation: relationship with osteoprotegerin levels.

We prospectively assessed the evolution of coronary artery calcification (CAC) and osteoprotegerin (OPG) levels after renal transplantation (RT). Eighty-three recipients were followed-up prospectively during 1 year. Blood was collected before (baseline) and after RT for determination of mineral metabolism parameters including OPG. CAC was measured by multidetector computed tomography at transplantation (baseline) and 1 year later. Progression of CAC was defined as a difference between the follow-up square-root transformed volume (SRV) and the baseline SRV >or= 2.5. By multivariate analysis, baseline OPG level, age and low LDL levels were significantly associated with baseline CAC. RT was accompanied by mineral metabolism improvement with a decrease of OPG from 955 [395-5652] to 527 [217-1818] pg/mL and parathyroid hormone from 94 [1-550] to 62 [16-410] pg/mL. Thirty-one percent of patients did not exhibit CAC at baseline. CAC diminished in 14.5%, stabilized in 59.2% and progressed in 26.3% of patients. Baseline CAC was associated with progression (OR 2.92 [1.02-8.36]). No significant association was found between OPG and CAC progression despite a higher baseline OPG level in progressors (1046 [456-3285]) vs. non-progressors (899 [396-5952] pg/mL). CAC at baseline, but not 1 year after RT, is independently associated with baseline OPG; posttransplant CAC progression is predicted by baseline CAC score.

Protein biochip array technology to monitor rituximab in rheumatoid arthritis.

In rheumatoid arthritis (RA) there are currently no good indicators to predict a clinical response to rituximab. The purpose of this study was to monitor and determine the role of peripheral blood cytokine profiling in differentiating between a good versus poor response to rituximab in RA. Blood samples were collected at baseline and at 3 months from 46 RA patients who were treated with rituximab. Responders are defined by the presence of three of four American College of Rheumatology criteria: >or=20% decrease in C-reactive protein, visual analogical score of disease activity, erythrocyte sedimentation rate and improvement of the disease activity score (28) (four values) by >or=1.2 obtained at 3 months. Twelve cytokines were measured from serum collected on days 0 and 90 by proteomic array, including interleukin-6 (IL-6), tumour necrosis factor-alpha, IL-1a, IL-1b, IL-2, IL-8, interferon-gamma, IL-4, IL-10, monocyte chemoattractant protein-1, epidermal growth factor and vascular growth factor. We showed that C-reactive protein and IL-6 levels decrease significantly at 3 months in the responder group compared with baseline. At day 90 we identified a cytokine profile which differentiates responders and non-responders. High serum levels of two proinflammatory cytokines, monocyte chemoattractant protein-1 and epidermal growth factor, were significantly higher in the responder group at day 90 compared with non-responders. However, we were not able to identify a baseline cytokine profile predictive of a good response at 3 months. These findings suggest that cytokine profiling by proteomic analysis may be a promising tool for monitoring rituximab and may help in the future to identify responder RA patients.

Multi-site, multi-country evaluation of analytical and operational performance of a low-mid volume chemiluminescent immunoassay analyzer.

BACKGROUND: A new automated immunoassay low-mid volume (< or = 250 immunoassays/day) chemiluminescent analyzer, Abbott Architect i1000sR, was evaluated by seven laboratories around the world (4 in Europe, one each in Canada, Japan, and the U.S.A.) to demonstrate equivalent performance for key operating characteristics (e.g., precision, turn around time, limit of detection, functional sensitivity, and linearity). METHODS: The laboratories followed standard protocols to assess precision, limit of detection (LoD), functional sensitivity, assay linearity, method comparison, and sample carryover. Turn around time for three stat assays (beta-hCG, BNP, and CK-MB) and the time required to complete workloads of 50 and 100 tests with a mixture of 75% routine tests and 25% stat tests was also evaluated. RESULTS: Total precision was typically < 5% CV for nine immunoassays. Analytical performance met design goals and demonstrated equivalency to package insert data for assays on market and in use for an existing high volume immunoassay system. Stat turn around times were consistent with the fixed analytical time of 15.6 minutes and met the expectations of the laboratories. Measured test throughput ranged from 47 - 54 tests per hour and demonstrated that the analyzer was fit for the intended purpose of supporting a laboratory that performs < or = 250 immunoassays per day. CONCLUSIONS: A multisite, international analyzer familiarization study is a practical means of confirming that a new instrument meets both a manufacturer's design specifications and users' real world expectations and provides a pragmatic test for the system. The experience of investigators at seven sites around the world indicates that a new fully automated chemiluminescent system is suitable for use.

Calcineurin Inhibitor Determination in Whole Blood With the RXL Dimension Analyzer: A Useful Tool for Immunosuppressive Drug Monitoring.

Routine monitoring of cyclosporine and tacrolimus levels is necessary to minimize adverse side effects and to ensure effective immunosuppression. The RXL Dimension apparatus conceived for ACMIA technologies is proposed to determine C0 and C2 cyclosporine levels and also tacrolimus levels in whole blood without any dilution or pretreatment using specific calibrators and Flex reagent cartridges (reagent stability: 72 hours for Neoral C0 and C2; 48 hours for tacrolimus). The assay ranges were between 25 to 500 ng/mL for C0; 350 to 2000 ng/mL for C2; and 1.2 to 30 ng/mL for tacrolimus. Within-run and between-day imprecision were <10% for cyclosporine. The coefficient of linearity was r(2) = .998 for C0, C2, and tacrolimus. Moreover, for cyclosporine and tacrolimus assays, the time for the first result was 20 minutes. Cyclosporine (C0, n = 152; C2, n = 54) and tacrolimus (n = 70) ACMIA assays were compared with enzyme-multiplied immunoassay technique (EMIT) cyclosporine and tacrolimus assays (V-Twin, Siemens ex-Dade Behring Laboratories) among 276 transplant patients: 119 kidney, 67 liver, 28 heart, and 62 bone marrow transplantations. Values obtained with the ACMIA assay were highly correlated with the EMIT assay for CsA C0 levels (ACMIA = 1.04 EMIT - 9.32; r(2) = .97); CsA C2 levels (ACMIA = 1.15 EMIT - 53.7; r(2) = .94); and tacrolimus levels (ACMIA = 0.93 EMIT - 0.16; r(2) = .93). In conclusion, the RXL Dimension analyzer is a useful tool for routine monitoring with a single method for C0 and C2 cyclosporine and tacrolimus level determinations in whole blood without any dilution or preanalytic treatment.

[Hematocrit measurement: comparison of conductimetry to microcentrifugation]. / Mesure de l'hématocrite: comparaison de la conductimétrie à la microcentrifugation.

In general, blood gas analysers can also determine the value of haematocrite by measuring the blood's conductivity. The question to ask is whether this value is reliable. In this study, hematocrit obtained via conductivity from 6 different pieces of equipment were compared with those measured using the gold standard method, which is microcentrifugation. By interpreting the results of 320 arterial blood samples taken in the intensive care unit DAR "B" we can see that the reliability between two measurements on the same piece of equipment is very good, in general > 0.95 whatever the equipment. The reliability between the means of the two measurements and the gold standard is slightly lower but remains very satisfactory, most often between 0.8 and 0.9. The Gem Premier 3000 (IL) analyser and the Roche OMNI S gave the best reliability compared with centrifugation. The Spearman coefficients between the mean values of the analysers and those of centrifugation were high, with the exception of the Rapidpoint 405. They are all statistically different from zero (p<0.0001).

[Carbonyl stress and oxidatively modified proteins in chronic renal failure]. / Stress carbonylé et modifications oxydatives des protéines au cours de l'insuffisance rénale chronique.

Oxidative stress is commonly observed in chronic renal failure patients resulting from an unbalance between overproduction of reactive oxygen species and impairement of defense mechanisms. Proteins appear as potential targets of uremia-induced oxidative stress and may undergo qualitative modifications. Proteins could be directly modified by reactive oxygen species which leads to amino acid oxydation and cross-linking. Proteins could be indirectly modified by reactive carbonyl compounds produced by glycoxidation and lipo-peroxidation. The resulting post-traductional modifications are known as carbonyl stress. In addition, thiols could be oxidized or could react with homocystein leading to homocysteinylation. Finally, tyrosin could be oxidized by myeloperoxidase leading to advanced oxidative protein products (AOPP). Oxidatively modified proteins are increased in chronic renal failure patients and may contribute to exacerbate the oxidative stress/inflammation syndrome. They have been involved in long term complications of uremia such as amyloidosis and accelerated atherosclerosis.

Improved quality of samples and laboratory turnaround time using 3.5 mL low vacuum BD Vacutainer® Barricor tubes in the emergency department.

BACKGROUND: Centrifugation is a consuming time step which participates to increase the turnaround time (TAT) in laboratories, likewise hemolysis sample that needs a re-sampling could delay management of patients. Recently, it has been postulated that BD Barricor™ tube could allow to decrease the centrifugation time and prevent hemolysis, two key feature to ensure high-quality results.Aim of the study was to evaluate the impact of replacing 4 mL BD vacutainer heparin lithium tube by low vacuum 3.5 mL BD vacutainer Barricor™ tube in an emergency department (ED) on hemolysis rate and TAT. METHODS: Data of hemolysis index (HI) and TAT were compared between the first period of 15 days using 4 mL BD vacutainer heparin lithium tubes with 15 min at 2000xg as centrifugation setting and a second period of 15 days using BD vacutainer Barricor™ tube centrifuged 3 min at 4000xg. RESULTS: A significantly reduced time duration between reception of sample and available results in informatics lab system was observed with the reduction time of centrifugation allowed by use of Barricor™ tube compared to regular heparin lithium tubes (p < 0.001). A significative decrease in hemolysis rate also occurred in the second period as samples with HI < 10 reached from 52.5% in the first period to 68.5% (p < 0.001) in the second. CONCLUSION: Low vacuum BarricorTM tubes allowing a higher speed of centrifugation improve lab TAT without impairment of sample quality as a significant reduction of hemolysis was observed, a double advantage which is of particular interest for ED.

Protein biochip array technology for cytokine profiling predicts etanercept responsiveness in rheumatoid arthritis.

In rheumatoid arthritis (RA) there are currently no useful indicators to predict a clinical response to tumour necrosis factor-alpha (TNF-alpha) blockade. The purpose of this study was to determine the role of peripheral blood cytokine profiling in differentiating between a good versus poor response to etanercept in RA. Peripheral blood samples were collected at baseline and at 3 months from 33 patients with active disease who were treated twice weekly by etanercept therapy. Responders are defined by the presence of three of four American College of Rheumatology criteria: > or =20% decrease in C-reactive protein (CRP), visual analogue score of disease activity, erythrocyte sedimentation rate and improvement of the disease activity score (28; four values) by > or =1.2 obtained at 3 months. Twelve cytokines were measured from serum collected on days 0 and 90 by proteomic array (protein biochip array, Investigator Evidence, Randox France), including interleukin (IL)-6, TNF-alpha, IL-1a, IL-1b, IL-2, IL-8, interferon-gamma, IL-4, IL-10, monocyte chemoattractant protein (MCP)-1, epidermal growth factor (EGF) and vascular endothelium growth factor. Our results showed that high serum levels of MCP-1 and EGF were associated with a response to etanercept. In addition, the increase of two combined parameters CRP and EGF was predictive of a response to etanercept treatment at 3 months (sensitivity: 87.5% and specificity: 75%, accuracy: 84.4%). These findings suggest that cytokine profiling by proteomic analysis before treatment initiation may help to identify a responder patient to TNF-alpha blocking agents in RA.

[Evaluation of renal function: an update]. / Evaluation de la fonction rénale: une actualisation.

During the last years, GFR estimation has received substantial attention with a focus on comparing results of new formulas with GFR measurements, and standardization of creatinine assays. Calibration of creatinine should improve performances. However, frequently used equations have lower precision in high GFR populations. This is the reason why a continuous effort in improving predicting equations is still needed. The use of calibrated creatinine, the onset of new GFR markers such as cystatin C, and pooling data across many study populations are underway to develop better prediction.

[Consequences for clinical biochemists of the modifications of the creatinine-based evaluation of glomerular filtration rate between 2005 and 2008]. / Evolution des modalités d'évaluation de la fonction rénale basée sur la créatinine entre 2005 et 2008: conséquences pour les biologistes.

Since 2005, international guidelines propose a stadification for chronic renal failure based on the glomerular filtration rate (GFR) value. The performance of the creatinine-based equations allowing the estimation of GFR and the bias of the creatinine measurements is, more than ever, a crucial issue. The consequences for the clinical biologists are of importance. First, the Cockcroft-Gault formula must be replaced by the four variable-MDRD equation. Second, the biologists must chose from the "175" and the "186" versions of the MDRD equation. The first one fits the creatinine methods which are traceable to the reference method (liquid or gas chromatography coupled to mass spectrometry). The second equation must be used for creatinine methods, which are not traceable to the reference method. Today, only some enzymatic methods can prove that they are traceable to the reference method. For the colorimetric methods, future is inclear.

[Cystatin C: current step and future prospects]. / Cystatine C: point d'étape et perspectives.

Cystatin C is a low molecular weight-protein, which may replace creatinine for the evaluation of renal function, particularly in the clinical settings where the relationship between creatinine production and muscular mass impairs the clinical performance of creatinine. This paper intends to summarize the current knowledge about the physiology of cystatin C and about its use as a renal marker, alone or within formulas developed to estimate the glomerular filtration rate. Moreover, this paper reviews the recent data about potential other applications of cystatin C, especially in cardiology, in oncology and in clinical pharmacology.

Dietary fat and the risk of age-related maculopathy: the POLANUT study.

This study aimed at assessing the associations of dietary fat with the risk of age-related maculopathy (ARM), in the framework of a population-based study from southern France. Nutritional data were collected using a dietitian-administered food-frequency questionnaire. ARM was classified from retinal photographs using the international classification and included neovascular age-related macular degeneration, geographic atrophy, soft indistinct drusen, soft distinct drusen associated with pigmentary abnormalities. After multivariate adjustment, high total, saturated and monounsaturated fat intake were associated with increased risk for ARM (odds ratio (OR)=4.74, P=0.007; OR=2.70, P=0.04; and OR= 3.50, P=0.03, respectively). Total polyunsaturated fatty acid was not significantly associated with ARM. Total and white fish intake was not significantly associated with ARM, but fatty fish intake (more than once a month versus less than once a month) was associated with a 60% reduction in risk for ARM (OR=0.42, P=0.01).

Waist circumference adds to the variance in plasma C-reactive protein levels in elderly patients with metabolic syndrome.

BACKGROUND: C-reactive protein (CRP), a nonspecific marker of the inflammatory status, is associated with cardiovascular disease risk factors and may be an important feature of the metabolic syndrome (MSX) in middle-aged subjects. OBJECTIVES: We assessed the relationship of CRP levels to specific components of MSX and other potential determinants in apparently healthy elderly subjects living in the South of France. METHODS: In the framework of the population-based POLA (Pathologies Oculaires Liées à l'Age) Study, performed in 2,404 subjects aged 60 years or more, we measured the plasma CRP levels. All subjects with known systemic inflammatory diseases, such as chronic bronchitis, cardiovascular disease, and diabetes, and those who were on systemic steroid therapy as well as subjects with CRP levels >10 mg/l were excluded from the study, leaving 1,709 subjects for the statistical analyses. MSX was defined according to NCEP (National Cholesterol Education Program) criteria. Other potential determinants were assessed through interviewer-based questionnaire. RESULTS: We grouped the subjects into three categories based on the 75th and 25th percentiles, corresponding to 3.05 and 0.82, respectively. We compared subjects in the highest quartile, i.e., with CRP >/=3.05 mg/l, with those in the two intermediate quartiles, i.e., with 0.82 < CRP < 3.05, and those in the lowest quartile, i.e., with CRP <0.82 mg/l according to gender. MSX, which had a prevalence of 31%, was significantly associated with elevated CRP levels. Among MSX components, the strongest positive association with the highest quartile of CRP was with waist circumference in males as well as in females (age-adjusted odds ratio OR 3.06 and 95% confidence interval CI 1.82-5.14; OR 7.04 and 95% CI 4.79-10.34, respectively). Each component of the MSX, such as abnormal fasting plasma glucose (OR 2.90, 95% CI 1.69-4.99), triglycerides (OR 1.96, 95% CI 1.30-2.96), high-density lipoprotein cholesterol (OR 2.31, 95% CI 1.61-3.30), and blood pressure (OR 1.66, 95% CI 1.12-2.45), was significantly associated with high CRP values in elderly women only. In men, only current smoking was significantly associated with high CRP levels (OR 1.52, 95% CI 1.04-2.2). In multivariate analysis, the waist circumference remained significantly associated with high CRP levels, with a graded effect of CRP quartile whatever the gender. In men, current and former smoking remained significantly associated with the CRP levels. In women, the association observed in univariate analysis with fasting glucose or hypertension did not reach statistical significance in the multivariate analysis, while only a weak association could be observed with lipid parameters such as triglycerides and high-density lipoprotein cholesterol. CONCLUSIONS: Abdominal adiposity adds to the variance in plasma CRP levels in elderly patients with MSX. This suggests that weight loss or other interventions targeted at adipocyte-related inflammation may represent an important means to prevent subclinical inflammation in the elderly, bearing a high risk of cardiovascular disease.

Lipid and oxidative stress disorders in a rat model of chronic rejection.

Chronic allograft dysfunction is the primary cause of graft loss after the first posttransplant year. Graft arteriosclerosis, a main component of this pathology, has oxidative stress and interactions with lipid disorders as part of the pathogenesis. The objective of our study was to determine whether oxidative stress was associated with the vascular lesions observed in a rodent model of graft arteriosclerosis. Using model of orthotopic aortic allograft in the rat, the allotransplantation (A) group included 12 Sprague-Dawley donors to 12 Lewis recipients, and the isotransplantation (B) group. 12 Lewis donors to 12 Lewis recipients. The rats received no immunosuppressants or antioxidants. After 12 weeks, the rats were humanely killed and the aorta cryopreserved until analysis. Blood samples were drawn for lipid assessment and oxidative stress analysis. Tissue expression of NADPH oxidase was quantified by Western blot, determining the constitutive membrane unit (p22phox) and the cytosolic regulating unit (p67phox). We observed a greater increase in the plasma markers of oxidative stress in group A than group B but without lipid abnormalities. The expression of NADPH subunits p22phox and p67phox were similar in both groups. These results showed that oxidative stress was associated with vascular lesions in our aortic graft model, but the origin of oxidative stress seemed to be independent of the NADPH oxidase.

[Comparative study of six blood gas analysers]. / Etude comparative de six analyseurs de gaz du sang.

An evaluation process directed by the biochemistry department of the UHC of Montpellier about acquisition of blood gas analysers for a point of care testing in 10 different medical care services. The values obtained by the different measurement machines have been compared taking into account the intra and inter measures variabilities. In this work, the results of 4 machines tested: Rapid-point 405, GEM Premier 3000, i-STAT 1 (série 300) and ABL 77 are compared with one i-STAT (série 200) and one OMNI S already available in the laboratory. The study lasted one month (november 2004). Each week, the two machines of the laboratory was compared with a new analyser randomly chosen between the four machines tested. In this study, including 21000 values, the statistical tests have been applied under the hypothesis that none of the measurement machine could be a "gold standard". Beside the classical research of correlation between the different values, we added the research of concordance between machines and the application of imperfect gold standard method. A high level of statistic concordance was observed between the different analysers. So the equipment has been selected using biological, analytic and computing criteria.

[Sodium determination in biological fluids]. / Méthodes de dosage du sodium dans les liquides biologiques.

Electrolyte disorders are frequently observed in nephrology and intensive care unit department and Na determination is routinely performed in biochemistry laboratories. Three methods are currently available. Flame photometry remains the reference method. With this method the serum sample is diluted before the actual measurement is obtained. Results are expressed as molarity (per Liter of plasma). Potentiometric methods have an increasing importance due to the advances in ion sensitive (selective) electrodes (ISE). Whereas the instruments for routine chemical analysis typically use indirect potentiometry (involving te dilution of samples) to measure sodium levels, the equipment for measuring arterial blood gases use direct potentiometry without any dilution. Thus, results obtained with indirect potentiometry are expressed in molarity (per liter of plasma) while results obtained with direct potentiometry are initially given in morality (per kg of plasma water) then converted in molarity. Analytical performances are in all cases satisfactory and therefore all the methods could be used in both normal and pathological ranges. Methods involving sample dilution such as flame photometry or indirect potentiometry, the serum sodium value would be expected to be low in case of decrease plasma water (pseudohyponatremia). By contrast, with direct potentiometry where no sample dilution takes place, no interference would be expected since the activity of sodium in the water phase only is being measured. Thus, the classical pseudohyponatremia observed with hyperlipemia or paraproteinemia are not further observed with direct potentiometry. These differences in methodology should be taken into account to explain discrepancies between results obtained with classical biochemistry analyser and with blood gas apparatus.

[Residual renal function in dialysis patients]. / Rôle de la fonction rénale résiduelle dans la balance sodée du dialysé: est-ce un bénéfice ou un risque?

Residual renal function (RRF) contributes to the achievement of treatment adequacy in CKD-5 patients. It may facilitate patients' acceptance of renal replacement therapy (RRT) in minimizing dietary and fluid restriction. It has been confirmed to improve dialysis patient outcomes. Attempts to preserve RKF in incident CKD-5 patients are still subject to controversies. In this review we analyze the role of RRT in dialysis patient. What are the positive and the beneficial effects of maintaining RRF? What are the negative and the risks of maintaining a RRF? At what expense the maintenance of RRF is achieved? Preservation of RRF is undoubtedly an interesting means to enhance the efficacy of renal replacement therapy and reduce dietary fluid restriction. However, maintainance of RRF should not be considered as a goal of dialysis adequacy in dialysis patients but rather a means of optimizing RRT. Further, preservation of RRF should be considered as a permanent trade-off between patient comfort and chronic fluid volume overload with its deleterious effects.