NMR measurement of LDL particle number using the Vantera® Clinical Analyzer

BackgroundThe Vantera Clinical Analyzer was developed to enable fully-automated, high-throughput nuclear magnetic resonance (NMR) spectroscopy measurements in a clinical laboratory setting. NMR-measured low-density lipoprotein particle number (LDL-P) has been shown to be more strongly associated with cardiovascular disease outcomes than LDL cholesterol (LDL-C) in individuals for whom these alternate measures of LDL are discordant.ObjectiveThe aim of this study was to assess the analytical performance of the LDL-P assay on the Vantera Clinical Analyzer as per Clinical Laboratory Standards Institute (CLSI) guidelines.ResultsSensitivity and linearity were established within the range of 300–3500 nmol/L. For serum pools containing low, medium and high levels of LDL-P, the inter-assay, intra-assay precision and repeatability gave coefficients of variation (CVs) between 2.6 and 5.8%. The reference interval was determined to be 457–2282 nmol/L and the assay was compatible with multiple specimen collection tubes. Of 30 substances tested, only 2 exhibited the potential for assay interference. Moreover, the LDL-P results from samples run on two NMR platforms, Vantera Clinical Analyzer and NMR Profiler, showed excellent correlation (R² = 0.96).ConclusionsThe performance characteristics suggest that the LDL-P assay is suitable for routine testing in the clinical laboratory on the Vantera Clinical Analyzer, the first automated NMR platform that supports NMR-based clinical assays.     

Comparison of low-density lipoprotein cholesterol concentrations measured by a direct homogeneous assay and by the Friedewald formula in a large community population

BackgroundWe compare the direct homogeneous low-density lipoprotein cholesterol (LDL-C) assay with the Friedewald formula (FF) for determination of LDL-C in a large community-dwelling population.MethodsA total of 21,194 apparently healthy subjects aged 40 to 79 years with triglyceride (TG) concentrations < 4.52 mmol/l were enrolled. LDL-C were directly measured by the enzymatic homogeneous assay (LDL-C (D)) and also estimated by the FF (LDL-C (F)). Paired t-test, Pearson's correlation coefficient and linear regression analysis were performed and the concordances of the National Cholesterol Education Program (NCEP) risk category were estimated.ResultsBoth in fasting (n = 3270) and nonfasting samples (n = 17,924), LDL-C (D) highly correlated with LDL-C (F): r = 0.971 and 0.955, respectively. Concordant results for NCEP categories were 84.8% for fasting samples and 80.1% for nonfasting samples. However, the bias between the 2 measurements increased in samples with TG concentrations > 1.69 mmol/l, especially in nonfasting samples.ConclusionsThe results showing less variability of the direct LDL-C assay than that of the FF in nonfasting samples suggest that epidemiological studies can use LDL-C measured by the direct assay both in fasting and nonfasting samples.     

Plasma proprotein convertase subtilisin–kexin type 9 is predominantly related to intermediate density lipoproteins

ObjectivesProprotein convertase subtilisin–kexin type 9 (PCSK9) is a key regulator of low density lipoprotein (LDL) receptor processing, but the PCSK9 pathway may also be implicated in the metabolism of triglyceride-rich lipoproteins. Here we determined the relationship of plasma PCSK9 with very low density lipoprotein (VLDL) and LDL subfractions.Design and methodsThe relationship of plasma PCSK9 (sandwich enzyme-linked immunosorbent assay) with 3 very low density lipoprotein (VLDL) and 3 low density lipoprotein (LDL) subfractions (nuclear magnetic resonance spectroscopy) was determined in 52 subjects (30 women).ResultsIn age- and sex-adjusted analysis plasma PCSK9 was correlated positively with total cholesterol, non-high density lipoprotein cholesterol and LDL cholesterol (r = 0.516 to 0.547, all p < 0.001), as well as with triglycerides (r = 0.286, p = 0.044). PCSK9 was correlated with the VLDL particle concentration (r = 0.336, p = 0.017) and with the LDL particle concentration (r = 0.362, p = 0.010), but only the relationship with the LDL particle concentration remained significant in multivariable linear regression analysis. In an analysis which included the 3 LDL subfractions, PCSK9 was independently related to intermediate density lipoproteins (IDL) (p < 0.001), but not to other LDL subfractions.ConclusionsThis study suggests that plasma PCSK9 predominantly relates to IDL, a triglyceride-rich LDL subfraction. The PCSK9 pathway may affect plasma triglycerides via effects on the metabolism of triglyceride-rich LDL particles.     

Estimation of the low-density lipoprotein (LDL) subclass phenotype using a direct,automated assay of small dense LDL-cholesterol without sample pretreatment

BackgroundA new method (sLDL-EX “SEIKEN”) is commercially available for the direct quantification of small dense LDL-cholesterol (sd-LDL) on automated chemistry analyzers, without manual sample pretreatment. We evaluated the performance of this direct assay to estimate the small dense LDL subclass phenotype (“non-A”), defined by polyacrylamide gel tube electrophoresis.MethodsFasting serum samples from 189 healthy subjects (age 18–75 y, 96 females) were collected. The direct sd-LDL assay (from Randox Laboratories) was applied on a Roche Modular P analyzer. The Quantimetrix Lipoprint^TM LDL System was used to define LDL subclass phenotypes (A and non-A). ROC curve analysis was performed for sd-LDL and other lipids and apolipoproteins (apo) with respect to phenotype non-A.Resultssd-LDL concentrations (40.4 ± 18.6 mg/dl) in the total group correlated (P < 0.0001) with apoB (r = 0.831), apoB/A-I ratio (r = 0.757), non-HDL-cholesterol (r = 0.821), triglycerides (r = 0.439), and LDL-cholesterol (r = 0.641). Higher sd-LDL concentrations (P < 0.0001) were measured in subjects with LDL phenotype non-A (53.6 ± 17.0 mg/dl, n = 92) than in those with phenotype A (27.9 ± 8.9 mg/dl, n = 97). In logistic regression analysis, sd-LDL and apoA-I were independently associated with LDL subclass phenotype non-A. Highest areas under ROC curves were obtained for sd-LDL (0.943), triglycerides (0.833), triglyceride/HDL-cholesterol (0.838) and apoB/A-I ratio (0.826) to predict phenotype non-A. The sd-LDL cut-off point for optimal sensitivity (87.9%) and specificity (92.8%) was > 38.5 mg/dl.ConclusionsThe direct, homogeneous sd-LDL method is easily applicable on an automated chemistry analyzer and shows acceptable performance to estimate the electrophoretic LDL subclass phenotype.     

Changes in lipid measures and incident coronary heart disease: Tehran Lipid & Glucose Study

BackgroundData on the impact of changes in lipid measures on subsequent coronary heart disease (CHD) outcomes are not consistent.MethodsStudy was conducted in 4459 adults, aged ≥ 30 years, free of cardiovascular disease at baseline who attended two consecutive examinations first in 1999–2001 and second in 2001–2003, and were followed up until March 31, 2010. Multivariate Cox proportional hazard regression adjusted for baseline lipid measures and other risk factors was calculated for a 1 standard deviation (SD) change in total cholesterol (TC), log-transformed triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) (calculated using modified Friedewald formula), non-HDL-C, TC/HDL-C and log-transformed TG/HDL-C. Effect of change in dyslipidemia (TC ≥ 6.21 mmol/L or TG ≥ 2.26 mmol/L or HDL-C < 1.03 mmol/L or non-HDL-C ≥ 4.91 mmol/L) on incident CHD was examined, considering those with no dyslipidemia at baseline and follow-up as the reference group.ResultsDuring a mean follow-up of 9.5 years, 303 cases of CHD occurred. A 1-SD increase in TC, TG, non-HDL-C, TC/HDL-C and TG/HDL-C was associated with 14, 20, 19, 16 and 14% increase in risk of CHD event, respectively (all p values < 0.05); the corresponding risk for LDL-C was [1.12 (0.99–1.27), P = 0.07]. Participants with maintained dyslipidemia during follow-up had a significant risk for incident CHD [HR: 1.67(1.21–2.49)] compared to those with no dyslipidemia at baseline or follow-up.ConclusionChanges in TC, TG, and non-HDL-C, TC/HDL-C, TG/HDL-C were independent predictors of CHD events. Furthermore, maintained dyslipidemia was a strong predictor for CHD events.     

Performance characteristics of a no-pretreatment,random access sirolimus assay for the Dimension® RxL clinical chemistry system

ObjectivesCurrent therapeutic drug monitoring methods for sirolimus require a manual pre-treatment step and batch analysis. We describe and validate a no-pretreatment, random access sirolimus assay for the Dimension® RxL clinical chemistry system from Siemens Healthcare Diagnostics Inc.Design and methodsWhole blood samples from renal transplant patients prescribed sirolimus were analyzed by the LC–MS/MS reference method, Abbott IMx and Dimension RxL methods in accordance with CLSI recommendations.ResultsThe Dimension sirolimus assay had a functional sensitivity of 2.0 ng/mL and repeatability and within-laboratory imprecision less than 12.6% at 3 ng/mL and less than 5% at 11–12 ng/mL. Least squares linear regression demonstrated the following relationships: RxL = 1.20(LC–MS/MS) – 0.70, r = 0.95 and RxL = 1.33(IMx) – 0.75, r = 0.96.ConclusionsThe Dimension sirolimus assay correlates well with the LC–MS/MS reference and IMx immunoassay methods and has the advantage of random access analysis without a manual pre-treatment step.     

Evaluation of the analytical performance of the Nova StatSensor creatinine meter and reagent strip technology for whole blood testing

ObjectiveTo evaluate the analytical performance of the Nova StatSensor creatinine meter.Design and methodsImprecision, linearity, patient correlation and interference studies were completed.ResultsTotal imprecision was 4.5–9.1%CV and a linear measurement range of 93–863 µmol/L (1.05–9.76 mg/dL) was verified. Whole blood creatinine results correlated well with laboratory plasma measurements (R² = 0.9328) but exhibited a negative proportional bias. In vitro, high levels of creatine and urea falsely elevated creatinine measurement.ConclusionsThe creatinine meter provides reliable measurement across a clinically relevant range and has potential use in point-of-care testing.     

Strict versus liberal insulin therapy in the cardiac surgery patient: An evidence-based practice development,implementation and evaluation project

BackgroundHyperglycemia post-cardiac surgery is associated with poor clinical outcomes. Recent studies suggest maintaining liberal glycemic control (< 180 mg/dL) using a continuous insulin infusion (CII) versus strict control achieves optimal outcomes and prevents hypoglycemia.PurposeTo develop, implement and evaluate a nurse managed liberal CII protocol.MethodsRetrospective review of 144 strict CII patient records and 147 liberal CII patient records.ResultsMean blood glucose was 159.8 mg/dL (liberal CII) compared to 143.3 mg/dL (strict CII) (p ≤ 0.001). No surgical site infections occurred in either group. Mean ICU length of stay was 4.5 days (liberal) versus 4.4 days (strict) (p = 0.74). Two 30-day mortalities occurred for the liberal cohort compared to no deaths in the strict group (p = 0.49). Hypoglycemia incidence within 24 h after surgery was 0.1% (liberal) compared to 0.3% (strict) compared to (p = 0.16).ConclusionUse of a nurse managed liberal CII resulted in similar outcomes with fewer incidents of hypoglycemia.     

Performance characteristics of an automated assay for the quantitation of CYFRA 21-1 in human serum

ObjectivesA fragment of cytokeratin 19, CYFRA 21-1, has been reported to be a sensitive tumor marker for non-small cell lung cancer (NSCLC). We describe analytical performance characteristics of a novel CYFRA 21-1 assay and hypothesize that CYFRA 21-1 complements the clinical sensitivity of carcinoembryonic antigen (CEA) and squamous cell carcinoma antigen (SCCa).Design and methodsPerformance characteristics of a CYFRA 21-1 immunochemiluminescent assay included analytical sensitivity, imprecision, linearity, analyte stability, and reference interval determination. Ninety-two pretreatment NSCLC serum samples were tested for CYFRA 21-1, CEA, and SCCa. Sensitivity was determined for each marker individually and in combination, with regard to tumor stage and histology.ResultsThe analytical sensitivity was 0.01 ng/mL. Total imprecision ranged from 4.0 to 6.3% at 4.9 to 28.4 ng/mL, respectively. The assay was linear from 0.9 to 71.4 ng/mL (slope = 0.995, intercept = ? 0.60, r² = 0.999). CYFRA 21-1 was stable for 48 h at ambient temperature and 14 days at 4 °C. The 97.5th percentile of a reference population was 1.9 ng/mL. Across disease stage, the sensitivities of CYFRA 21-1, CEA, and SCCa were 17–81%, 30–52%, and 24–39%, respectively. CYFRA 21-1 combined with CEA or SCCa increased sensitivity above that of any single marker.ConclusionsAn immunochemiluminescent assay for CYFRA 21-1 had favorable performance characteristics. CYFRA 21-1 was complementary to CEA and SCCa and increased clinical sensitivity in patients with NSCLC.     

A next generation enzymatic magnesium assay on the Abbott ARCHITECT chemistry system meets performance goals based on biological variation

ObjectiveTo evaluate the performance of the Abbott ARCHITECT enzymatic assay for magnesium (3P68) in serum/plasma and urine against analytical goals based on biological variation.MethodsAnalytical performance was evaluated according to CLSI protocols. Precision was examined using commercial chemistry controls. Accuracy was assessed against NIST SRM 956c, electrolytes in human serum. Correlation with the arsenazo Mg assay (7D70) was completed using patient samples (plasma, N = 101; urine, N = 90). Common interferences were examined in pooled patient specimens with high and low magnesium concentrations.ResultsThe enzymatic Mg assay displayed imprecision of 1.7% at 0.72 mmol/L and 1.4% at 1.80 mmol/L (20 days, one calibration, one reagent lot). The linear range was verified between 0.18–7.0 mmol/L (plasma) and 0.01–10.69 mmol/L (urine). Results of the enzymatic assay (x) correlated well with the predicate assay (y) with the relationships y = 0.891x + 0.035, R = 0.967 (plasma) and y = 1.181x + 0.086, R = 0.997 (urine). Mean bias of the NIST SRM 956c samples was − 1.4%. This method showed minimal interference by hemoglobin (3 g/L as hemolysate), lipemia (20 g/L Intralipid), unconjugated bilirubin (531 μmol/L), and ascorbate (680 μmol/L).ConclusionsThe ARCHITECT Magnesium assay 3P68 achieved the desirable analytical quality specification of 4.8% for total allowable error. In comparison to the 7D70 assay, notable improvements are seen in precision, 30-day calibration stability, and minimal interference by hemolyzed and lipemic samples.     

Efficacy and safety of a combination of red yeast rice and olive extract in hypercholesterolemic patients with and without statin-associated myalgia

Cholesfytol^®, a lipid-lowering dietary supplement with antioxidant and anti-atherosclerotic properties, combines red yeast rice (RYR) and olive extract (5 mg hydroxytyrosol equivalent) and represents an alternative for patients who do not wish or are unable to use chemical statins, including individuals with previous statin-associated muscle symptoms (SAMS). A 2-months observational non-randomized study was performed to evaluate the efficacy, tolerance and safety of Cholesfytol^® (1 tablet/day) in 642 hypercholesterolemic patients (mean age: 59 yrs; total cholesterol (TC) ≥200; LDL-C ≥140 mg/dl). Patients were followed by 126 GPs, and included irrespective of SAMS history and/or diabetes. None of the patients were taking statins or other lipid-modifying therapy at inclusion. At baseline, 26% had fasting glucose >100 ≤125 mg/dL, and 5% >125 mg/dL; 32% (n = 194) had a SAMS history; and 21% had atherogenic dyslipidemia (AD). In the entire cohort, pre-treatment TC; non-HDL-C; LDL-C; and TG were 259; 200; 168; 158 mg/dL, respectively, and decreased significantly on treatment (−17.5% (TC) and −23.3% (LDL-C)). Fasting glucose and HbA_1c decreased between visits. The reduction in lipids was greater in patients with higher values at baseline. For comparable pre-treatment values, patients with SAMS history had reductions in TC, LDL-C, non-HDL-C, and apoB₁₀₀ slightly less than patients without myalgia. AD patients had greater on-treatment decrease in TG. Overall, 13 patients reported minor side-effects, and 4 patients reporting myalgia had antecedent SAMS. In conclusion, a substantial decrease in LDL-C was obtained with a combination of RYR and olive extract in high-risk hypercholesterolemic patients, without inducing new-onset SAMS.     

Multicentric evaluation of the homogeneous LDL-cholesterol Plus assay: comparison with beta-quantification and Friedewald formula

ObjectivesTo evaluate the analytical and clinical performance of a new version of the LDL-C Plus assay and compare it with the beta-quantification (BQ) method in a multicenter study.Design and methodsDirect LDL-C was measured in 169 fresh pooled samples and in 830 clinical samples with known LDL-C by BQ. The reactivity of lipoproteins and the effect of hemoglobin, bilirubin and chylomicrons (CM) were studied.ResultsDirect LDL-C total imprecision was < 2.2%; inaccuracy < ± 2.5% (unaffected by triglycerides up to 9.5 mmol/L); and total error 9.8%. Direct assay reacted with 95%, 50% and 25% of the cholesterol in the LDL, intermediate (IDL) and VLDL fractions, respectively. A significant association was observed with BQ. Icteric samples showed a negative bias and the effect of CM was variable. A positive bias was observed when VLDL-cholesterol/triglyceride ratio was > 0.57.ConclusionsLDL-C Plus assay represents a valid alternative to BQ for clinical laboratories.     

Diagnostic utility of a single-epitope sandwich B-type natriuretic peptide assay in stable coronary artery disease: Data from the Akershus Cardiac Examination (ACE) 1 Study

ObjectivesTo assess the merit of a novel single-epitope sandwich (SES) assay specific to the stable part of BNP in patients with reversible myocardial ischemia as post-translational modifications of BNP may influence assay performance.Design and methodsWe measured BNP concentration by a conventional assay and the SES-BNP assay in 198 patients referred for myocardial perfusion imaging (MPI). BNP concentration was determined before and immediately after exercise stress testing, and 1.5 and 4.5 h later. Patients were categorized according to MPI results.ResultsBNP concentration was higher with both assays at all time points in patients with reversible myocardial ischemia (n = 19) compared to the other patients (n = 179). Measuring BNP after stress testing or calculating the changes in BNP concentration did not improve diagnostic accuracy compared to baseline measurements: SES-BNP: AUC 0.71 (95% CI 0.58–0.84) vs. conventional BNP: 0.71 (0.59–0.83), p = 0.96. By linear regression analysis, reversible myocardial ischemia was significantly associated with baseline SES-BNP concentration (p = 0.043), but not with measurements by the conventional assay (p = 0.089). In multivariate logistic regression models, only baseline measurement with the SES-BNP assay was significantly associated with reversible myocardial ischemia: odds ratio [logarithmical transformed BNP] 2.00 (95% CI 1.16–3.47), p = 0.013. The SES-BNP assay, but not the conventional BNP assay, reclassified a significant proportion of the patients towards their correct category on top of the best clinical model of our data set: NRI = 0.47, p = 0.04.ConclusionsThe SES-BNP assay was significantly associated with reversible myocardial ischemia as assessed by several statistical indices, while a conventional BNP assay was not.     

Evaluation of a new homogenous method for detection of small dense LDL cholesterol: Comparison with the LDL cholesterol profile obtained by density gradient ultracentrifugation

BackgroundSmall, dense LDL (sdLDL) are highly atherogenic, and evidence indicates that sdLDL are useful predictors of cardiovascular disease. We evaluated a homogeneous method for the quantitative determination of sdLDL cholesterol (sdLDL-C) and compared it to the LDL-cholesterol profile obtained by density gradient ultracentrifugation (DGUC).MethodssdLDL-C was measured in plasma and in lipoprotein fractions obtained by DGUC using the sdLDL-EX “Seiken” kit.ResultssdLDL-C was only present in dense or intermediate LDL fractions obtained by DGUC. Plasma sdLDL-C levels were inversely corelated to the LDL relative floatation rate. The proportion of LDL-C that is sdLDL-C increases as a function of LDL density from a median of 19% for very buoyant LDL to 91% for very dense LDL particles. Plasma sdLDL-C level was significantly correlated with plasma triglyceride (TG) (n = 840, r_s = 0.710, p < 0.001). Among subjects with plasma TG > 150 mg/dl, 75% had sdLDL-C > 30 mg/dl, whereas among those with TG ≤ 150 mg/dl, only 17% had sdLDL-C > 30 mg/dl.ConclusionsThis precise and fully automated method for measuring plasma levels of sdLDL-C will allow the analysis of large number of samples in routine laboratories which will facilitate the evaluation of the clinical usefulness of sdLDL as a risk factor for CHD.     

Establishment of reference intervals for soluble ST2 from a United States population

BackgroundSoluble ST2 (sST2) is a protein in the interleukin-1 receptor family secreted by myocytes in response to mechanical strain. Elevated sST2 is strongly prognostic in patients with heart failure.MethodssST2 was measured using the Presage? ST2 ELISA. Evaluation included imprecision, linearity, recovery, analytical sensitivity, limit of quantification, stability, and sample type comparisons. Gender-specific reference intervals were established from 245 male and 245 female serum specimens.ResultsAt sST2 concentrations of 11.6, 26.9, and 88.0 ng/mL, the within-day CV was 7.6, 2.4, and 3.8%, respectively and the total CV was 11.5, 14.0, and 6.3%, respectively. The assay was linear over a concentration range of 2.8–161.1 ng/mL (y = 0.95x + 2.25; R² = 0.997; Sy.x = 3.03). The limit of quantification was 3.3 ng/mL. sST2 was stable for 2 days at room temperature, 10 days at 4 °C, and 30 days at ?20 °C. Concentrations of sST2 were significantly higher in males compared to females (24.9 vs. 16.9 ng/mL; p < 0.0001) but were not correlated by age in either gender (r = ?0.07; p = 0.14). Reference intervals for sST2 were determined to be 8.6–49.3 and 7.2–33.5 ng/mL for males and females, respectively.ConclusionThe Presage? ST2 ELISA had acceptable performance characteristics for quantifying sST2 in serum or plasma. The assay is precise and linear over a wide sST2 concentration range and can measure low sST2 concentrations. Concentrations of sST2 are unaffected by age but are higher in males compared to females.     

Evaluation of five immunoturbidimetric assays for urinary albumin quantification and their impact on albuminuria categorization

ObjectivesThe study was designed to evaluate the performance of five automated immunoturbidimetric assays to quantify urinary albumin, each corresponding to a combination of a reagent and an analyzer (Olympus on AU640®, Roche on Cobas Integra, Abbott on Architect, Ortho-Clinical Diagnostics Vitros on Fusion and Siemens on Dimension).Design and methodsTo assess imprecision, albumin was measured in three urinary pools with a mean value of 25, 66 and 131 mg/L. One hundred and eight patient urine samples were then used to compare each turbidimetric method using the Passing–Bablok regression and Bland–Altman analyses. Concordance of the albumin/creatinine ratio (ACR), according to the albuminuria classifications proposed by the KDIGO, was calculated to test the agreement between the different assays.ResultsAll immunoturbidimetric methods evaluated in this study exhibited acceptable imprecision (CV < 6%). Mean values for 108 urine samples varied from 0.5 to 762.2 mg/L. Significant differences were found (p < 0.05) between all methods except between Olympus and Ortho (p = 1.0) and between Abbott and Roche (p = 0.12). Regarding the albuminuria categories based on the ACR proposed by the KDIGO, only the classification obtained with the Roche method was significantly different from the four other methods (p < 0.001).ConclusionsWe demonstrated that all assays were not strictly equivalent which could affect ACR categories in clinical practice, suggesting the need for harmonization of commercial methods.     

BiliChek transcutaneous bilirubin meter overestimates serum bilirubin as measured by the Doumas reference method

ObjectivesTo determine the relationship between BiliChek TcB (Respironics, Marietta GA) and Doumas reference serum or plasma total bilirubin (TSB).Design and methodsPooled samples with values assigned by the Doumas reference method were used to establish the relationship between a local laboratory and reference Doumas TSB. We then established the relationship between TcB and TSB in the 3 months before and after reassignment of calibrator setpoints undertaken to match the local laboratory to Doumas reference bilirubin values.ResultsBefore calibrator setpoint reassignment TSB as measured in our laboratory overestimated Doumas reference bilirubin. After calibrator adjustment laboratory TSB was within 1.7–6.8 µmol/L (0.1–0.4 mg/dL) of Doumas reference values. Mean bias between BiliChek TcB and TSB was 42.8 ± 22.2 µmol/L (2.5 ± 1.3 mg/dL) (n = 94) before and 49.6 ± 22.2 µmol/L (2.9 ± 1.3 mg/dL) (n = 115) after calibration adjustment.ConclusionsBiliChek TcB significantly overestimates TSB as measured by the Doumas reference method.     

Omega-3 fatty acids improve postprandial lipemia and associated endothelial dysfunction in healthy individuals – a randomized cross-over trial

BackgroundPostprandial elevation of triglycerides impairs endothelial function and contributes to the development of atherosclerosis. We investigated the effects of omega-3 fatty acids on postprandial endothelial function and lipid profiles.MethodsHealthy volunteers [10] were given supplementation at 4 g/day omega-3 fatty acids (or were not treated) for 4 weeks in a randomised crossover study. Postprandial levels of various lipids were monitored and endothelial function assessed by brachial artery flow-mediated dilation during fasting and after a standard cookie test.ResultsOmega-3 fatty acids reduced postprandial endothelial dysfunction compared with the control diet (flow-mediated dilation at 4 h = −0.5 ± 1.2 vs. −2.0 ± 1.6%, P = 0.03). Postprandial levels of triglycerides, apolipoprotein B-48, and remnant lipoprotein-cholesterol increased in untreated subjects, peaked at 2–4 h, and returned to baseline at 8 h, whereas low-density lipoprotein-cholesterol levels did not change. Supplementation with omega-3 fatty acids significantly suppressed postprandial elevation of triglycerides (incremental area under the curve = 220 ± 209 vs. 374 ± 216 mg/h/dL, P = 0.04) and remnant lipoprotein-cholesterol (incremental area under the curve = 21.7 ± 13.8 vs. 13.3 ± 12.9 mg/h/dL, P = 0.04). Supplementation with omega-3 fatty acids significantly suppressed the increase in triglyceride content in chylomicrons as well as in very-low-density lipoproteins from baseline to 4 h after the cookie test.ConclusionOmega-3 fatty acids significantly decreased postprandial triglyceride elevation and postprandial endothelial dysfunction, suggesting that omega-3 fatty acids may have vascular protective effects in postprandial state.     

Analytical evaluation of a high-molecular-weight (HMW) adiponectin chemiluminescent enzyme immunoassay

BackgroundThe measurement of high-molecular-weight (HMW) adiponectin concentration provides valuable clinical information. However, the conventional ELISA method requires complicated and lengthy assay procedures to obtain assay results.MethodsWe prepared new assay reagents based on chemiluminescent enzyme immunoassay (CLEIA) on a fully-automated analyzer system using the same IH7 monoclonal antibody as for ELISA as solid phase and detection antibodies (CLEIA/cartridge-type and CLEIA/bottle-type).ResultsThe assay range of both CLEIA reagents were from 0.20 to 15.00 μg/ml, and lower limit of detection and quantification were lower than 0.0928 and 0.1346 μg/ml in CLEIA/cartridge-type and in CLEIA/bottle-type reagents, respectively. A good correlation was observed between both reagents (y = 1.000x + 0.120). The imprecision test as % of coefficient variation in both reagents were less than 3.3% and recovery test showed the range from 100% to 109%. No or little interference of blood components was observed in both reagents. HMW adiponectin concentration measured by CLEIA reagents was approximately half that measured by the previous ELISA because of reevaluation using freshly and highly purified HMW adiponectin standard.ConclusionThe newly prepared CLEIA reagents are robust and adequate and can be used for the measurement of HMW adiponectin in the clinical laboratory.     

Validating urinary measurement of beta-2-microglobulin with a Roche reagent kit designed for serum measurements

ObjectiveTo validate the use of a Roche serum beta-2-microglobulin (B2MG) kit for urinary B2MG measurements, and to establish reference limits for urinary B2MG/creatinine ratio from healthy individuals.Design and methodsThe Roche B2MG Tina-Quant serum kit was used to measure urinary B2MG immunoturbidimetrically.ResultsUsing human urine as a diluent, the B2MG method was linear from 73–2156 μg/L. The imprecision on a commercially available urine QC was 4.4% at a concentration of 380 μg/L. Limit of quantification at < 20% CV was 40 μg/L. Method comparison with Immulite 2000 (Siemens) yielded slope = 1.180 (95% CI 1.14–1.22), intercept = 11.5 (95% CI ? 3.6–26.6), SEE = 27.6 and r = 0.99 (n = 26) by the Deming regression analysis. The upper reference limit of B2MG/creatinine ratio determined from 195 healthy adults was 29 μg/mmol (97.5th centile).ConclusionsThe serum B2MG Tina Quant reagent kit is acceptable to measure urinary B2MG.