Establishing age and sex dependent upper reference limits for the plasma lipoprotein (a) in a Chinese health check-up population and according to its relative risk of primary myocardial infarction.

BACKGROUND: Though lipoprotein (a) (Lp (a)) has been considered as a risk factor for coronary artery disease, there is a lack of cutoff values of Lp (a) for Chinese Han ethnicity. METHODS: We included 1 population for health check-ups. Lp (a) percentile distributions were analyzed and its cutoff for Chinese Han ethnicity was also proposed according to the its relative risk of myocardial infarction. RESULTS: Lp (a) distributions differed between sexes, and were highly skewed towards low concentrations with a long tail towards the highest ones. The relative risks of elevated Lp (a) concentrations for myocardial infarction had an inflection in Chinese Han ethnic at the 8th decile, corresponding to 167 mg/l, where the risk was prone to be increased. In terms of Lp (a) median concentrations, per higher age quantile (5-y interval) was associated with a significant increase of 3.2 mg/l and females were on average 19.75 mg/l higher than males with a significant difference. CONCLUSIONS: We proposed Lp (a) < 170 mg/l after rounding as cut-off values for Chinese Han ethnicity. Effects of age and sex on Lp (a) concentrations were also noted. Prospective validation of these cutoff values is critically important in Chinese Han ethnicity.

Utility of currently recommended pediatric dyslipidemia classifications in predicting dyslipidemia in adulthood: evidence from the Childhood Determinants of Adult Health (CDAH) study, Cardiovascular Risk in Young Finns Study, and Bogalusa Heart Study.

BACKGROUND: New age- and sex-specific lipoprotein cut points developed from National Health and Nutrition Examination Survey (NHANES) data are considered to be a more accurate classification of a high-risk lipoprotein level in adolescents compared with existing cut points established by the National Cholesterol Education Program (NCEP). The aim of this study was to determine which of the NHANES or NCEP adolescent lipoprotein classifications was most effective for predicting abnormal levels in adulthood. METHODS AND RESULTS: Adolescent and adult measures of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides were collected in 365 Australian, 1185 Finnish, and 273 US subjects participating in 3 population-based prospective cohort studies. Lipoprotein variables in adolescence were classified according to NCEP and NHANES cut points and compared for their ability to predict abnormal levels in adulthood. With the use of diagnostic performance statistics (sensitivity, specificity, positive predictive value, negative predictive value, area under receiver operating characteristic curve) in pooled and cohort-stratified data, the NHANES cut points (compared with NCEP cut points) were more strongly predictive of low high-density lipoprotein cholesterol in adults but less predictive of high total cholesterol, high low-density lipoprotein cholesterol, and high triglyceride levels in adults. We identified heterogeneity in the relative usefulness of each classification between cohorts. CONCLUSIONS: The separate use of NHANES cut points for high-density lipoprotein cholesterol and NCEP cut points for total cholesterol, low-density lipoprotein cholesterol, and triglycerides yielded the most accurate classification of adolescents who developed dyslipidemia in adulthood.

Developmental haemostasis. Impact for clinical haemostasis laboratories.

Developmental haemostasis is a concept, now universally accepted, introduced by Andrew et al. in the late 1980's. However, coagulation analysers and reagents have changed significantly over the past 15 years. Coagulation testing is known to be sensitive to changes in individual reagents and analysers. We hypothesised that the reference ranges developed by Andrew et al. may not be appropriate for use in a modern coagulation laboratory. Our study was designed to determine whether a current day coagulation testing system (STA Compact analyser and Diagnostica Stago reagent system) was sensitive to age-related changes in coagulation assays. This is the first large scale study since Andrew et al. to determine the age associated numerical changes in coagulation proteins. Our results confirm the concepts of developmental haemostasis elucidated by Andrew et al. However, our results clearly demonstrate that the absolute values of reference ranges for coagulation assays in neonates and children vary with analyser and reagent systems. The results confirm the need for coagulation laboratories to develop age-related reference ranges specific to their own testing systems. Without this, accurate diagnosis and management of neonates and children with suspected bleeding or clotting disorders is not possible. Finally we present age related reference ranges for D-dimers, TFPI, and endogenous thrombin potential, previously not described.

Lipid, lipoprotein, apolipoprotein and lipoprotein(a) levels: reference intervals in a healthy Indian population.

The role of lipids, lipoproteins and lipoprotein(a) [Lp(a)] in coronary artery disease (CAD) is known but the role of major apolipoproteins (apos) other than apo A-I and apo B remains unclear. In this study, using immunoturbidimetry we have estimated serum levels of total cholesterol, HDL-C, LDL-C, triglyceride, LDL-apoB and all major apos; A-I, A-II, B, C-II, C-III and E, in 751 healthy Indian subjects (470 men and 281 women, age 25-65 years), determined their percentiles, and established reference intervals. The effects of age, smoking and alcohol on all these analytes were also evaluated. This is the first study to provide reference intervals for all apos, in both sexes from a general population. The percentiles and the reference intervals have clinical relevance and will be useful in assessing the risk of CAD in patients with hyperlipidemia and other diseases.

Micafungin: the US perspective.

Invasive fungal infections cause considerable morbidity and mortality in nosocomial settings and amongst immunocompromised hosts. Invasive candidiasis and aspergillosis remain the most common invasive fungal infections, with Candida spp. constituting the fourth most common bloodstream infection in the USA. Currently available antifungal therapies include the polyene, antimetabolite, allylamine, azole and echinocandin drug classes. Micafungin, approved in March 2005 by the Food and Drug Administration for use in the USA, has shown safety and efficacy for the treatment of candidiasis and aspergillosis in clinical trials in Japan, Europe and South Africa. Micafungin holds promise as a first-line treatment option for candidiasis, as well as prophylaxis against invasive fungal infections during periods of neutropenia in high-risk patients.

Measurement of cholesterol and other lipoprotein constituents in the clinical laboratory.

Measurements of lipids and lipoproteins in the clinical laboratory have become increasingly important because of their predictive association with cardiovascular diseases, especially coronary artery disease. The US National Institutes of Health-sponsored National Cholesterol Education Program and counterparts in other countries have developed national consensus guidelines for diagnosis and treatment of coronary artery disease which provide risk cut-points and define use of the lipid/lipoprotein analytes in case finding and therapy. Total and low density lipoprotein cholesterol and triglycerides are measured as positive risk factors and high density lipoprotein cholesterol as an inverse risk factor for coronary artery disease. A National Cholesterol Education Program-sponsored expert laboratory panel has developed guidelines for measurements with requisite analytical performance targets for total error and corresponding precision and bias. The US Centers for Disease Control and Prevention have established reference methods for total and high density lipoprotein cholesterol and for triglycerides, with a method for low density lipoprotein cholesterol in development. Standardization programs for research laboratories and a Cholesterol Reference Method Laboratory Network for diagnostic manufacturers and clinical laboratories provide reliable access and documentation of traceability to accepted reference methods. Methods for the lipid/lipoprotein analytes have improved dramatically in recent years and, coupled with improved chemistry analyzer systems and more attention to standardization by manufacturers, offer considerable improvement in analytical performance. Fully automated homogeneous assays for high density lipoprotein cholesterol and newer similar assays for low-density lipoprotein cholesterol have potential for better precision as well as more convenient and cost-effective measurements. Attention to pre-analytical sources of variation is also important in making reliable classification of patients.

Laboratory standardization of a large international clinical trial: the DAIS experience. DAIS Project Group. Diabetes Atherosclerosis Intervention Study.

OBJECTIVE: To implement a quality control program for the standardization and harmonization of lipid and lipoprotein analyses as performed at two core laboratories (St. Paul's Hospital, UBC [Vancouver], and NPHI [Helsinki]) for the Diabetes Atherosclerosis Intervention Study (DAIS). DESIGN AND METHODS: A DAISSOFT computer program was designed to minimize the occurrence of data and sample management errors during the course of the study. Fresh human serum was used for the provision of an accuracy based external quality control program that monitored the analytical performance of lipid testing at these two laboratories. A separate program was designed for monitoring hemoglobin A1c (HbA1c). At the outset of the study, allowable total error goals were established for each analyte. Ongoing performance was monitored using bimonthly blinded challenges of fresh human serum. The two EQA programs routinely monitored the analysis of total cholesterol, calculated LDL-cholesterol, HDL-cholesterol, net triglycerides, apoprotein A-1, apoprotein B, and HbA1c. RESULTS: The EQA precision and accuracy data for the measurement of total cholesterol at the two core laboratories over the last 5 years indicated both laboratories operated with good precision, approximately 1% CV over the time period. The accuracy at both laboratories was similar initially. Part way through the study, the accuracy of the cholesterol method at NHPI tended to drift upward with an operating positive bias (+3%) relative to the Abell Kendall reference method. Triglyceride measurements were the most problematic for the study. By EQA cycle 8, the accuracy of the method at UBC had stabilized and was meeting the accuracy goals of the study. NPHI's method was negatively biased relative to the accuracy base of the DAIS study. In spite of recalibrating their method, NPHI found it difficult to maintain consistent accuracy for the measurement of triglycerides during the study. Both laboratories operated their HDL methods with excellent precision. Accuracy at NHPI was well maintained over the course of the study whereas the accuracy of HDL measurements at UBC was more problematic. There was an inconsistent variation in the accuracy of apoprotein A-1 measurements at both laboratories. In most cases, the bias would be corrected by the time of the next EQA challenge. In the case of apo B, one laboratory was standardized to the CDC while the other laboratory was standardized to IFCC/WHO. The discrepancy between these two accuracy bases was >20%. Recalibration to a common accuracy base rectified the problem. Only minor problems were encountered with the precision and accuracy of the DIAMAT assay for hemoglobin A-1c. The two DAIS core laboratories consistently operated within the 9% total error goals of the study for HbA1c. CONCLUSIONS: Through the use of this program, the two DAIS core laboratories were able to maintain their lipid analyses within the limits of allowable total error that had been established for the study.

Reference intervals and decision limits for plasma lipids and lipoproteins: a practical evaluation of current recommendations.

As part of a longitudinal study--the Kristianstad Survey--we measured plasma cholesterol, HDL- and LDL-cholesterol, triglycerides and lipoprotein (a) in a reference group consisting of 203 men and women aged 20-80, randomly sampled from a well-defined area in the southernmost part of Sweden. The selection of reference individuals and the collection of specimens for assay of the constituents were performed in accordance with current recommendations. The results were subjected to statistical analyses both with and without application of exclusion criteria. Application of the theoretical exclusion criteria resulted in the exclusion of 22% of the participants; however, this procedure had a remarkably weak impact on the results: the mean values and the standard deviations were almost unaltered. The mean (standard deviation) for cholesterol was 5.9 (1.3) mmol l-1, for HDL-C 1.1 (0.3) mmol l-1, and for LDL-C 4.3 (1.2) mmol l-1. Women had higher values than men. Plasma triglycerides were positively skewed; their median and Q3-Q1-values were 1.0 and 0.5 mmol l-1 respectively, men higher than women. There was an increase with age for cholesterol and LDL-C in both sexes and for triglycerides in women. The steepest increase of cholesterol values with age in women coincided with menopause, which have a more clear-cut separation between high and low cholesterol values than did any age limit.

Enzyme-linked immunoassay for Lp[a].

Based on our findings that rabbit antisera raised against human Lp[a] or apo[a] have the potential to cross-react with plasminogen, and in some cases have nearly equal affinities for plasminogen and Lp[a], we have developed an assay for plasma Lp[a] based on a "sandwich" ELISA that is insensitive to the presence of plasminogen. This was accomplished through the use of anti-apo[a] as a capture antibody and quantitation of the bound Lp[a], i.e., the apoB-100-apo[a] complex, with an anti-apoB antibody. Although apo[a] is heterogeneous in size, all Lp[a] particles tested, either in pure form or contained in whole plasma, gave parallel dose-response curves and were immunologically equivalent. However, when purified Lp[a] particles with different apo[a] isoforms were studied, those having larger isoforms were, on a weight basis, less reactive than those having a smaller size. Nearly equivalent reactivity was observed when protein concentration was expressed on a molar basis. The distribution of Lp[a] in a population of 84 subjects was skewed with one-third of the individuals having less than 1 mg/dl Lp[a] protein. All subjects tested had measurable concentrations of Lp[a] with a lower limit of detection of 0.030 mg/dl Lp[a] protein. The mean level was 3.2 mg/dl with a range of 0.045 to 13.3 mg/dl. These studies demonstrate the successful development of an ELISA for Lp[a] protein that is insensitive to the presence of plasminogen; that heterogeneity of Lp[a] and apo[a] are an important source of variation in the assay; and the need for an appropriate Lp[a] standard in order to minimize this variation.

Automated enzymatic standardized lipid analyses for plasma and lipoprotein fractions.

Excellent normal ranges for plasma lipid and lipoprotein cholesterol levels have been developed by the Lipid Research Clinics program, standardized by the Centers for Disease Control (CDC). However these values were generated by methods not currently in use in most clinical chemistry laboratories. Automated enzymatic methods for cholesterol, triglycerides and free glycerol determinations, as well as a dextran sulfate-Mg2+ procedure for separation of high density lipoproteins (HDL) with standardization are described. Similar methods for the measurement of unesterified cholesterol and phospholipids are also given. Serum pools for total cholesterol with values ranging from 1220-3490 mg/l produced coefficients of variation (CV) less than or equal to 2.85%; reference values for low total cholesterol samples in a range of 280-727 mg/l gave CV of 4.35% or less; HDL cholesterol reference values of 265-640 mg/l yielded CV less than or equal to 3.70%; and values for triglycerides between 0.74 and 3.05 mmol/l gave CV of 4.22% or less through three to eight testing cycles (9-24 mth). These data indicate that long term CDC standardization of total cholesterol, triglycerides, and HDL cholesterol can be obtained with automated enzymatic methods utilizing commercially available reagents.