Establishment of reference intervals of clinical chemistry analytes for the adult population in Egypt.

BACKGROUND: This is the first Egyptian nationwide study for derivation of reference intervals (RIs) for 34 major chemistry analytes. It was conducted as a part of the global initiative by the IFCC Committee on Reference Intervals and Decision Limits (C-RIDL) for establishing country-specific RIs based on a harmonized protocol. METHODS: 691 apparently healthy volunteers aged ≥18 years were recruited from multiple regions in Egypt. Serum specimens were analyzed in two centers. The harmonization and standardization of test results were achieved by measuring value-assigned serum panel provided by C-RIDL. The RIs were calculated by parametric method. Sources of variation of reference values (RVs) were evaluated by multiple regression analysis. The need for partitioning by sex, age, and region was judged primarily by standard deviation ratio (SDR). RESULTS: Gender-specific RIs were required for six analytes including total bilirubin (TBil), aspartate and alanine aminotransferase (AST, ALT). Seven analytes required age-partitioning including glucose and low-density lipoprotein cholesterol (LDL-C). Regional differences were observed between northern and southern Egypt for direct bilirubin, glucose, and high-density-lipoprotein cholesterol (HDL-C) with all their RVs lower in southern Egypt. Compared with other collaborating countries, the features of Egyptian RVs were lower HDL-C and TBil and higher TG and C-reactive protein. In addition, BMI showed weak association with most of nutritional markers. These features were shared with two other Middle Eastern countries: Saudi Arabia and Turkey. CONCLUSION: The standardized RIs established by this study can be used as common Egyptian RI, except for a few analytes that showed regional differences. Despite high prevalence of obesity among Egyptians, their RVs of nutritional markers are less sensitive to increased BMI, compared to other collaborating countries.

The distributions of hematologic and biochemical values in healthy high-school adolescents in Japan.

Laboratory tests of adolescents are often interpreted by using reference intervals derived from adults, even though these populations differ in their physical and physiologic characteristics and disease susceptibility. Therefore, to examine the distribution of laboratory values specific for adolescents, we analyzed hematologic and biochemical measurements obtained from 12,023 healthy Japanese adolescents (ages 15 through 18 years; male, 9165; female, 2858) during 2009 through 2018. Distributions were shown as medians with 95% (2.5th and 97.5th percentiles) of values and were compared with those from previous studies that examined similar Asian populations. There were some differences between hematologic parameters, serum creatinine and uric acid concentration, and lipid levels of Japanese adults and adolescents. In comparison with other Asian populations, the distributions of serum uric acid and high-density-lipoprotein cholesterol in the present study were slightly higher than those in the other studies. Although further research is need, the distributions of hematologic and biochemical tests in adolescents may have the potential to facilitate the early identification and management of disease in this population.

Calibration of High-Density Lipoprotein Cholesterol Values From the Korea National Health and Nutrition Examination Survey Data, 2008 to 2015.

BACKGROUND: For correct interpretation of the high-density lipoprotein cholesterol (HDL-C) data from the Korea National Health and Nutrition Examination Survey (KNHANES), the values should be comparable to reference values. We aimed to suggest a way to calibrate KNHANES HDL-C data from 2008 to 2015 to the Centers for Disease Control and Prevention (CDC) reference method values. METHODS: We derived three calibration equations based on comparisons between the HDL-C values of the KNHANES laboratory and the CDC reference method values in 2009, 2012, and 2015 using commutable frozen serum samples. The selection of calibration equation for correcting KNHANES HDL-C in each year was determined by the accuracy-based external quality assurance results of the KNHANES laboratory. RESULTS: Significant positive biases of HDL-C values were observed in all years (2.85-9.40%). We created the following calibration equations: standard HDL-C=0.872×[original KNHANES HDL-C]+2.460 for 2008, 2009, and 2010; standard HDL-C=0.952×[original KNHANES HDL-C]+1.096 for 2012, 2013, and 2014; and standard HDL-C=1.01×[original KNHANES HDL-C]-3.172 for 2011 and 2015. We calibrated the biases of KNHANES HDL-C data using the calibration equations. CONCLUSIONS: Since the KNHANES HDL-C values (2008-2015) showed substantial positive biases compared with the CDC reference method values, we suggested using calibration equations to correct KNHANES data from these years. Since the necessity for correcting the biases depends on the characteristics of research topics, each researcher should determine whether to calibrate KNHANES HDL-C data or not for each study.

Importancia de la dislipidemia en la enfermedad cardiovascular: un punto de vista / Importance of dyslipidaemia in cardiovascular disease: a point of view

Los autores exponen su punto de vista sobre la prevención de las enfermedades cardiovasculares, aceptando los criterios europeos ESC/EAS. Consideran que el objetivo del control lipídico, basado en objetivos de cLDL, es básico para la prevención y el tratamiento de la enfermedad cardiovascular. En sujetos con síndrome metabólico (fundamentalmente obesidad abdominal, prediabetes y diabetes) el objetivo primario debería ser apoB o el cNo-HDL, que se correlacionan mejor con el riesgo cardiovascular. El tratamiento debe establecerse con modificaciones del estilo de vida y control de otros factores de riesgo. Tras el cálculo del riesgo cardiovascular, en los casos indicados utilizaremos estatinas, con la potencia y dosis necesaria para conseguir objetivos. Si no se consiguen objetivos, se añadirá ezetimiba o resinas. Los anticuerpos monoclonales anti-PCSK-9, recientemente aprobados en España, constituyen una interesante opción. En sujetos de muy alto riesgo cardiovascular, una vez alcanzados los objetivos de cLDL o los de apoB/cNo-HDL, se valorará añadir otros fármacos (fibratos, ácidos grasos omega-3) capaces de modificar los triglicéridos y el cHDL. El tratamiento para reducir el riesgo cardiovascular y prevenir la enfermedad cardiovascular ha demostrado efectividad en todas las poblaciones y edades. En los sujetos mayores de 80 años deberá valorarse individualmente la situación y las morbilidades asociadas para decidir su utilización

The authors present their view on the prevention of cardiovascular diseases, accepting the European ESC/EAS guidelines. They consider that the aim of the lipid control, based on LDL-C goals, is essential for the prevention and treatment of cardiovascular diseases. In subjects with metabolic syndrome (mainly, abdominal obesity, pre-diabetes and diabetes), the primary objective should be apoB or Non-HDL-C, which are better associated with cardiovascular risk. The treatment must be lifestyle changes and control of other risk factors. After calculating cardiovascular risk, statins are the first therapeutic step, with the strength and dose needed to achieve LDL-C goals. If targets are not achieved, ezetimibe or resins should be added. A new group of potent cholesterol-lowering agents, the PCSK-9 monoclonal antibodies, have recently been approved in Spain. Subjects at very high cardiovascular risk that have achieved LDL-C goals, or other objectives (apoB, Non-HDL-C), other drugs (fibrates, omega-3) capable of modifying triglycerides and HDL-C could be added, if necessary. Treatment to reduce cardiovascular risk and prevent cardiovascular disease has proven effective in all populations and at all age groups. Subjects older than 80 years should be individually assessed, taking into consideration possible comorbidities

Metabolic-cognitive syndrome: a cross-talk between metabolic syndrome and Alzheimer's disease.

A growing body of epidemiological evidence suggested that metabolic syndrome (MetS) and Mets components (impaired glucose tolerance, abdominal or central obesity, hypertension, hypertriglyceridemia, and reduced high-density lipoprotein cholesterol) may be important in the development of age-related cognitive decline (ARCD), mild cognitive impairment (MCI), vascular dementia, and Alzheimer's disease (AD). These suggestions proposed in these patients the presence of a "metabolic-cognitive syndrome", i.e. a MetS plus cognitive impairment of degenerative or vascular origin. This could represent a pathophysiological model in which to study in depth the mechanisms linking MetS and MetS components with dementia, particularly AD, and predementia syndromes (ARCD or MCI), suggesting a possible integrating view of the MetS components and their influence on cognitive decline. In the present article, we discussed the role of these factors in the development of cognitive decline and dementia, including underlying mechanisms, supporting their influence on ß-amyloid peptide metabolism and tau protein hyperphosphorylation, the principal neuropathological hallmarks of AD. In the next future, trials could then be undertaken to determine if modifications of these MetS components including inflammation, another factor probably related to MetS, could lower risk of developing cognitive decline. Future research aimed at identifying mechanisms that underlie comorbid associations of MetS components will not only provide important insights into the causes and interdependencies of predementia and dementia syndromes, but will also inspire novel strategies for treating and preventing cognitive disorders.

Measurement performance of reagent manufacturers by Centers for Disease Control and Prevention/Cholesterol Reference Method Laboratory Network lipid standardization specified for metabolic syndrome-focused health checkups program in Japan.

AIM: This study was designed to clarify the current measurement performance of 7 reagent manufacturers for high-density lipoprotein cholesterol (HDLC), low-density lipoprotein cholesterol (LDLC) and triglycerides (TG) specified for the metabolic syndrome (MetS)-focused health checkups program in Japan. METHODS: Twenty HDLC, 21 LDLC and 9 TG analytical reagent/instrument/calibrator systems (system), and combinations of reagent lots, instrument models and calibrator lots, underwent Centers for Disease Control and Prevention (CDC)/Cholesterol Reference Method Laboratory Network (CRMLN) lipid standardization. Eighty and 100% systems were requested to achieve an accuracy of within +/-1% and +/-2% of the reference value, so that a clinical laboratory can meet the CDC criteria. RESULTS: The CDC performance criteria of HDLC, LDLC and TG require an accuracy of within +/-5%, +/-4% and +/-5%, respectively. For HDLC, all 20 systems met the criteria. Fourteen (70.0%) and 18 (90.0%) systems were within +/-1% and +/-2%, respectively. For LDLC, 14 (66.7%) of 21 systems met the criteria, but 7 (33.3%) failed. Five (23.8%) and 17 (81.0%) systems were within +/-1% and +/-2%, respectively. For TG, 8 of 9 systems met the criteria. Two (22.2%) and 4 (44.4%) systems were within +/-1% and +/-2%, respectively. The minimum and maximum differences of a specified sample among manufacturers were 1.6 and 11.0 mg/dL for HDLC, 7.8 and 33.0 mg/dL for LDLC, and 2.8 and 27.4 mg/dL for TG, respectively. CONCLUSION: Homogeneous HDLC methods are acceptable for MetS, but further accuracy improvement of homogeneous LDLC and TG methods will be needed because of their poor performance.

Prevalence and extent of dyslipidemia and recommended lipid levels in US adults with and without cardiovascular comorbidities: the National Health and Nutrition Examination Survey 2003-2004.

BACKGROUND: Despite improvements in low-density lipoprotein cholesterol (LDL-C) levels, recent national data are limited regarding the proportion of adults at recommended lipid levels according to the presence of cardiovascular disease (CVD) and related comorbidities. We evaluated the proportion of US adults with and without these conditions at (and distance to) recommended levels of LDL-C, non-high-density lipoprotein cholesterol (non-HDL-C), HDL-C, and triglycerides. METHODS: We analyzed data from adults aged > or =20 who had fasted for 8 or more hours (n = 2,883, weighted to a US population of 128.5 million) in the National Health and Nutrition Examination Survey 2003-2004, a nationally representative cross-sectional survey. The number of adults at National Cholesterol Education Program recommended levels for LDL-C, non-HDL-C, HDL-C, triglycerides, and combined lipids, stratified by sex, age group, ethnicity, and the presence of CVD comorbidities was determined. RESULTS: Although 85% to 89% of persons without CVD or related comorbidities were at recommended levels for LDL-C, non-HDL-C, HDL-C, and triglycerides, only 36% to 37% of those with CVD or related comorbidities were at recommended levels for LDL-C and non-HDL-C, and only 17% were at recommended levels for all lipids. Treated persons compared with those untreated had significantly lower LDL-C (112.3 vs 156.7 mg/dL, P < .001) and non-HDL-C levels (145.9 vs 188.7 mg/dL, P < .001), but similar HDL-C (52.0 vs 50.1 mg/dL, P = .09) and triglyceride (160.1 vs 148.7 mg/dL, P = .20) levels. CONCLUSIONS: Despite improved LDL-C levels, many adults, especially with CVD or related comorbidities, are not at recommended levels for all lipids. Improved treatment efforts to target the spectrum of dyslipidemia are needed.

Lipid external quality assessment: commutability between external quality assessment and clinical specimens.

BACKGROUND: Targets for cholesterol reduction are part of the Quality Outcomes Framework and general practitioners have to meet these targets to fulfil their remuneration package. By contrast, there are no targets for the accuracy of cholesterol or other lipid measurements and no recent surveys on performance of these assays. We have assessed the performance of lipid measurement of the available methods in the UK. METHODS: Serum samples collected from individual donors attending the national blood service were distributed after values were obtained from a secondary reference laboratory. Samples were sent to participant laboratories to assess different methods' analytical performance on single donation specimens, on routine external quality assessment pooled specimens, on specimens subjected to a range of freeze-thaw cycles and on frozen-stored specimens. RESULTS: Differences in measured cholesterol were found that were method-dependent and related to triglyceride content. HDL-cholesterol (HDL-C) showed significant positive bias in all assays. Individual donor specimens showed no significant changes with differing numbers of freeze-thaw cycles. Pooled serum was stable for up to six months. CONCLUSIONS: Most cholesterol measurements are accurate but some methods are affected by triglyceride interference. HDL-C methods show significant positive bias. Although there are potential matrix effects introduced as a result of specimen preparation, additional work is needed to show if these effects are present in fresh patient samples.

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.

Commutability assessment of potential reference materials using a multicenter split-patient-sample between-field-methods (twin-study) design: study within the framework of the Dutch project "Calibration 2000".

BACKGROUND: The Dutch project "Calibration 2000" aims at harmonization of laboratory results via calibration by development of commutable, matrix-based, secondary reference materials. An alternative approach to the NCCLS EP14 protocol for studying commutability of reference materials is presented, the "twin-study design", which in essence is a multicenter, split-patient-sample, between-field-methods protocol. METHODS: The study consisted of the simultaneous analysis of fresh patient sera and potential reference materials (PRMs) for HDL-cholesterol (HDL-C) by 86 laboratories forming 43 laboratory couples. Six subgroups of method combinations were formed. The patient sera were selected and interchanged by each laboratory couple. The PRMs consisted of three types: C37, prepared according to the NCCLS C37 protocol; Fro, frozen selectively pooled human serum; and Lyo, which was the same serum pool as Fro but lyophilized in the presence of sucrose. All PRMs were provided in three HDL-C concentrations. The regression line residuals for the PRMs were normalized by expressing them as multiples of the state-of-the-art within laboratory SD (SD(SA)). In addition, the extra contribution of each PRM to the total measurement uncertainty, CV(Netto), was calculated. RESULTS: Averaged over the three PRM concentrations, 1.6% of the C37 residuals were outside the 3 SD(SA) limit. For the Fro and Lyo PRMs, these values were 2.4% and 11.1%. CV(Netto) values for C37, Fro, and Lyo were 2.9%, 4.3%, and 5.3%, respectively. CONCLUSIONS: The present twin-study design, as a practical alternative to the NCCLS EP14 protocol, is a viable way of studying commutability characteristics of PRMs. The study suggests that the C37 PRMs are the best candidates for a future reference material.

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.

Survey of total error of precipitation and homogeneous HDL-cholesterol methods and simultaneous evaluation of lyophilized saccharose-containing candidate reference materials for HDL-cholesterol.

BACKGROUND: Standardization of HDL-cholesterol is needed for risk assessment. We assessed for the first time the accuracy of HDL-cholesterol testing in The Netherlands and evaluated 11 candidate reference materials (CRMs). METHODS: The total error (TE) of HDL-cholesterol measurements was assessed in native human sera by 25 Dutch clinical chemistry laboratories. Concomitantly, the suitability of lyophilized, saccharose-containing CRMs (n = 11) for HDL-cholesterol was evaluated. RESULTS: In the precipitation method group, which included 25 laboratories and four methods, the mean (minimum-maximum) TE was 11.5% (2.7-25.2%), signifying that 18 of 25 laboratories satisfied the TE goal of

Assessment of interlaboratory performance in external proficiency testing programs with a direct HDL-cholesterol assay.

Direct assays for the determination of HDL-cholesterol (HDL-C) have recently become available. The methods are precise, require small sample volume, and appear to be less affected by increased triglycerides than traditional precipitation methods. In this study, we describe the inter- and intralaboratory variability of the Boehringer Mannheim Corporation direct HDL-C assay and its performance in external proficiency testing surveys. A comparison study among three laboratories, using different analyzers and 85 serum specimens, showed a correlation coefficient (r) of 0.99. The direct HDL-C assay also showed good agreement with the ultracentrifugation-dextran sulfate-Mg2+ method (r = 0.98) and the Cholesterol Reference Method Laboratory Network-Designated Comparison Method (a = 0.98x + 4.75 mg/L, r = 0.98). Total error at medical decision levels ranged from -0.8% to +11.1%. Furthermore, this assay performed adequately in the College of American Pathologists and the ALERT surveys as well as the CDC Lipid Standardization Program and met all performance criteria of regulatory agencies.

[Standardization of the methods of lipid determination according to WHO in the regional project of prevention of cardiovascular diseases in Friuli-Venezia Giulia]. / La standardizzazione dei metodi per la determinazione dei lipidi secondo l'OMS, nel progetto regionale di prevenzione delle malattie cardiovascolari del Friuli-Venezia Giulia.

BACKGROUND: The recognition of dyslipidemias as a major modifiable risk factor for atherosclerosis and coronary heart disease underlines the need to obtain precise and accurate assay results of plasma lipids. Today the use of automatic laboratory methods and of internal quality control favours the precision of the results but does not guarantee accuracy. The efficiency of a laboratory can be ensured by a standardization programme, systematically monitoring precision and accuracy by means of independent internal and external quality control, international reference standards (e.g. those of CDC-NHLBI and WHO) and protocols to identify and reduce the errors due to biological variability and pre-analytical factors. After the foundation of the Regional Project for Prevention of Cardiovascular Diseases in Friuli-Venezia Giulia, a lipid standardization programme was set-up, covering the 20 chemico-clinical laboratories of the Region. The programme was directed by the International WHO-MONICA-Lipid Reference Centres of Prague-Udine. METHODS: During the years 1993-1994, three sets of lyophilized human serum samples were dispatched to each laboratory for the blind evaluation of total cholesterol, triglycerides and HDL-cholesterol. The samples were obtained by the combination of three serum pools at least at different lipid concentration. The first set included 20 samples to be tested in 5 weeks, the second set included 30 samples to be tested in 8 weeks and the third set included 21 samples to be tested in 9 weeks. The assay results were sent to the Prague-Udine WHO-MONICA Centres where they were computerized and evaluated, particularly considering precision for each set, estimated by the variation coefficient (i.e. standard deviation/mean value of the measurements per cent) and accuracy (the bias was computed as mean of the measurement minus the reference value/reference value per cent). RESULTS: In the three assay series for total cholesterol, almost all the laboratories showed the variation co-efficient (precision) to be less than the WHO-MONICA limit of 3.7% (for a cholesterol level of 250 mg) (Tab. II) and in 8 cases out of 20, less than the CDC limit of 3%; the accuracy bias was less than the WHO-MONICA limit of 5% in 17 laboratories out of 20 and less than the CDC limit of 3% in 11 cases out of 20. For the HDL-cholesterol standardization programme the reference values were based upon the phosphotungstate method. However, the pools were also controlled by the other precipitation methods used in the 20 participating laboratories: 11 laboratories worked within the WHO-MONICA limits of precision and accuracy (respectively 6.5% and 7.5%) in at least two of the three sets. Concerning triglycerides, the regional laboratories showed a greater variability and, though most of the variation coefficients were within the WHO-MONICA limit of 5%, half of the accuracy biases were greater than the limit of 10%. The bias of the measurement average of all the laboratories was excellent for total and HDL-cholesterol, not quite good but acceptable for triglycerides. Laboratory performance improved progressively from the first to the last set, on more than one occasion. CONCLUSIONS: The lipid standardization experience carried out in the framework of the Regional Project for Prevention of Cardiovascular Disease demonstrates that it is possible to set up a wide and co-ordinated collaboration with laboratories of an entire region with positive and improving results. For this global quality control system, the resource allocated is limited but widely rewarded by the community benefits in terms of assay reliability and savings at medical care level, basic research and population studies.

Regional interlaboratory standardization of determinations of cholesterol, high-density lipoprotein cholesterol, and triglycerides.

The Clinical Chemistry Forum of Central Virginia initiated a lipid standardization program to help ensure that its members meet the current National Cholesterol Education Program guidelines for cholesterol testing, and to standardize assays of high-density lipoprotein (HDL) cholesterol and triglycerides so as to provide accurate lipid profiles. We found that freshly collected, never-frozen human sera must be used to assess interlaboratory accuracy for cholesterol, HDL cholesterol, and triglycerides assays, and that at least 23 samples are required to detect a 3% bias with 90% power when the between-laboratory imprecision (CV) is 3%. After recalibration, all 12 laboratories had a mean HDL cholesterol bias less than or equal to 5%, nine of 10 laboratories had a mean HDL cholesterol bias less than or equal to 40 mg/L for samples with values less than or equal to 570 mg/L, and 10 of 12 laboratories had a mean triglycerides bias less than or equal to 10% for fresh human sera split between participants and the Centers for Disease Control. Pools of frozen human sera were shown to have matrix biases greater than 3% for cholesterol in seven of 11 laboratories, and greater than 40 mg/L for HDL cholesterol in six of nine laboratories.