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.

Monthly reference change value of cardiac troponin in hemodialysis patients as a useful tool for long-term cardiovascular management.

PURPOSE OF RESEARCH: Circulating cardiac troponin (cTn) has been identified as a risk factor for cardiovascular and overall mortality in patients undergoing hemodialysis. However, its interpretation remains difficult due to the high prevalence of patients with cTn level beyond the 99th percentile. Determining the cTn reference change value (RCV) may help in assessing a clinically significant change of cTn during regular follow-up of patients. We aimed to determine the long-term RCV of cTn in such patients and to calculate the perdialytic reduction rate of cTn. DESIGN AND METHODS: To calculate RCV, high-sensitivity (hs)-cTnT (Roche), hs-cTnI (Abbott), and cTnI-ultra (Siemens) were determined every month before the midweek dialysis session over a 3-month period in 36 stable hemodialysis patients. cTn was also measured after the midweek dialysis session to calculate the cTn removal rate. RESULTS: The mean RCV (95% confidence interval) was 22% (18-26) for hs-cTnT versus 53% (34-73) for hs-cTnI versus 65% (45-84) for cTnI-ultra. Log-normal RCV (%) was -19/+25 for hs-cTnT, -33/+96 for hs-cTnI, and -39/+115 for cTnI-ultra. The index of individuality was <0.6 regardless of the cTn assay used. A significantly greater reduction rate was observed for hs-cTnT (48%) than for hs-cTnI (30%, p<0.001) and cTnI-ultra (29%, p<0.05). CONCLUSIONS: These results underline the need to use the RCV approach rather than cutoff points to identify the critical change in long-term serial cTn levels. In addition, RCV should be determined for each available assay due to significant differences between assays. Removal of cTn during hemodialysis sessions should also be considered if acute coronary syndrome is suspected during a session.

Long term reference change value of creatinine in HIV-positive patients with anti-retroviral therapy: A new tool in clinical practice.

BACKGROUND: The use of reference change value (RCV) instead of reference interval emerged as an alternative approach for longitudinal interpretation of biological marker. Follow-up of creatinine variation in HIV-positive adults remains a challenge in order to prevent renal complications. OBJECTIVES: To determine the long term RCV of creatinine in HIV-positive adults receiving anti-retroviral therapy (ART) according to the use of tenofovir or ritonavir. DESIGN AND METHODS: Longitudinal study of 24 months that include 124 HIV-positive patients followed in HIV outpatient unit. Plasma creatinine was measured at 0, 6, 12 and 24 months in order to calculate the RCV. RESULTS: In the whole group, a 24-month RCV of creatinine was 22.5%. Whatever the ART, the index of individuality was <0.6. Significantly higher RCV of creatinine was observed in patients receiving the association tenofovir and ritonavir (28%) compared to the patients receiving i) tenofovir without ritonavir (21.9%), ii) no tenofovir but ritonavir (22.2%), and iii) no tenofovir and no ritonavir (19.7%). CONCLUSIONS: The low value of index of individuality pinpointed that RCV should be used to identify critical change in serial creatinine results in HIV-positive adults. RCV of creatinine under ART was around 20% but reached 28% in case of association of tenofovir and ritonavir.

Accuracy of GFR predictive equations in renal transplantation: validation of a new turbidimetric cystatin C assay on Architect c8000.

OBJECTIVES: To evaluate the Sentinel-PETIA cystatin C on Architect c8000 analyzer. DESIGN AND METHODS: We assessed analytical performances and clinical relevance by comparison with a reference isotopic method in kidney transplant recipients. RESULTS: This assay exhibited reliable precision and was close to the non standardized Siemens-PENIA method. All tested equations allowed reliable assessment of GFR. CONCLUSIONS: Cystatin C improved GFR determination at the critical level of 60 mL/min/1.73 m². New formulas might be necessary after IFCC standardization.

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.

[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.

Renal transplantation decreases osteoprotegerin levels.

Vascular calcifications are an important risk factor for cardiovascular mortality and morbidity in patients with chronic renal failure. Osteoprotegerin, a soluble decoy receptor for receptor activator NFkB ligand, has emerged as an independent predictive factor of atherosclerosis and vascular calcification in hemodialysis patients. Sparse data are available on the evolution of osteoprotegerin after renal transplantation. The aim of this study was to follow the evolution of serum osteoprotegerin levels and biochemical risk factors after renal transplantation. Forty patients were included. Blood samples for analysis were collected before and 3 months after renal transplantation. Besides the expected diminution in calcium-phosphate product, we have shown an early normalization of osteoprotegerin (10.05 +/- 4.77 pmol/L to 4.59 +/- 2.26 pmol/L). This study demonstrates that kidney transplantation improves this risk factor for vascular calcifications. However, these preliminary results should be confirmed and extended by the follow-up of vascular calcifications in the long term.

Evaluation of an immunoassay (Abbott-IMX Analyzer) allowing routine determination of sirolimus: comparison with LC-MS method.

BACKGROUND: The use of the immunosuppressive agent sirolimus is increasing in renal transplantation but its monitoring often requires high-performance liquid chromatography (HPLC) with ultra-violet (UV) or tandem mass spectrometric (MS-MS) detection. The aim of this study was to compare a new microparticle enzyme immunoassay (MEIA, Microparticle Enzyme Immunoassay) on IMx Abbott Analyser with a liquid chromatography-mass spectometry (LC-MS) method. METHOD: The accuracy of immunoassay analytical performance including within run and between run imprecision and linearity was tested. For comparison studies, sirolimus level was then determined with the two methods on 98 samples from 52 transplant patients. RESULTS: Total intra-assay and inter-assay variation coefficients were below 10% at the three levels tested, and the coefficient of linearity was r = 0.99. The values obtained were highly correlated with the LC-MS method (MEIA = 1.02LC-MS + 0.91; r(2) = 0.87). As a result, the immunoassay showed good performance, and clinical sample measurements were not affected by the method. The MEIA may be a useful alternative for routine monitoring of sirolimus.

Immunonephelometric determination of fibrinogen on citrated or heparinized plasma: comparison with functional Clauss method.

BACKGROUND: Fibrinogen is routinely determined by functional assay on citrated plasma in the hematology department. However, immunoassay can be performed easily with nephelometric analyzer in the clinical chemistry laboratory allowing automatization. The aim of this study was first to compare the clotting von Clauss method (activity assay) with an immunonephelometric method (antigen assay) on the BN ProSpec (Dade Behring). Moreover, we evaluated the possibility of collecting blood samples on heparin to facilitate blood collection for clinicians and reduce required blood collection volumes for dosages. METHODS: In a first step of experiment, the accuracy of immunonephelometric analytical performance was tested on heparinized and citrated tubes. For comparison studies, fibrinogen activity was then determined on citrated tubes in the hematology department and antigen measurement was performed on both citrated and heparinized plasma from 130 consecutive patients. RESULTS: As a result, the immunonephelometric method shows reliable performance and clinical sample measurements are not affected by the method used, validating the use of heparinized plasma samples for fibrinogen antigen determination with Dade Behring reagents.