Verification of Low-Density Lipoprotein Cholesterol Levels Measured by Anion-Exchange High-Performance Liquid Chromatography in Comparison with Beta Quantification Reference Measurement Procedure.

BACKGROUND: A new lipoprotein testing method based on anion-exchange HPLC (AEX-HPLC) was recently established. We verified the accuracy of LDL-C levels, a primary therapeutic target for the prevention of cardiovascular disease (CVD), measured by AEX-HPLC comparing with LDL-C levels measured by beta quantification-reference measurement procedure (BQ-RMP), homogenous assays, and calculation methods. METHODS: We compared LDL-C levels measured by AEX-HPLC (adLDL-Ch: LDL-Ch and IDL-Ch) and BQ-RMP using blood samples from 52 volunteers. AdLDL-Ch levels were also compared with those measurements by homogeneous assays and calculation methods (Friedewald equation, Martin equation, and Sampson equation) using blood samples from 411 participants with dyslipidemia and/or type 2 diabetes. RESULTS: The precision and accuracy of adLDL-Ch were verified by BQ-RMP. The mean percentage bias [bias (%)] for LDL-C was 1.2%, and the correlation was y = 0.990x + 3.361 (r = 0.990). These results met the acceptable range of accuracy prescribed by the National Cholesterol Education Program. Additionally, adLDL-Ch levels were correlated with LDL-C levels measured by the 2 homogeneous assays (r > 0.967) and the calculation methods (r > 0.939), in serum samples from patients with hypertriglyceridemia. CONCLUSIONS: AEX-HPLC is a reliable method for measuring LDL-C levels for CVD risk in daily clinical laboratory analyses.

A method for measuring glycerol-blanked triglyceride concentrations by using gas chromatography-isotope dilution mass spectrometry.

BACKGROUND: Serum triglyceride concentrations are measured as total glycerides content in many Western countries. In Japan, glycerol-blanked triglycerides (TG-GB) are measured to identify postprandial hypertriglyceridaemia and to minimize the influence of glycerol formulation on serum triglyceride values. However, TG-GB measurements have not been standardized. Therefore, we developed an efficient quantification system for total glycerides and free glycerol that allows the calculation of TG-GB concentrations. METHODS: We measured total glycerides and free glycerol in human serum by using gas chromatography-isotope dilution mass spectrometry and compared its performance to the reference method of the US Centers for Disease Control and Prevention (CDC). RESULTS: Our practical method of total glycerides and free glycerol quantification achieved excellent precision for both within-run and among-run coefficients of variation (<1.5% and <2.7%, respectively), with an average recovery of 99.8% for free glycerol. However, we noted an average %bias of -0.26% for total glycerides and -3.15% for free glycerol between our TG-GB method and the CDC reference method. CONCLUSIONS: This practical method of total glycerides and free glycerol quantification enables traceability assessment of TG-GB measurements. Differences between the output values of TG-GB and the CDC reference method might result from the differences in free glycerol values.

Total cholesterol performance of Abell-Levy-Brodie-Kendall reference measurement procedure: Certification of Japanese in-vitro diagnostic assay manufacturers through CDC's Cholesterol Reference Method Laboratory Network.

BACKGROUND: Accurate measurement of total cholesterol (TC) is important for cardiovascular disease risk management. The US Centers for Disease Control and Prevention (CDC) and Cholesterol Reference Method Laboratory Network (CRMLN) perform Abell-Levy-Brodie-Kendall (AK) reference measurement procedure (RMP) for TC as a secondary reference method, and implement Certification Protocol for Manufacturers. Japanese CRMLN laboratory at Osaka performed the AK RMP for 22 years, and conducted TC certification for reagent/calibrator/instrument systems of six Japanese manufacturers every 2 years for 16 years. Osaka TC performance was examined and compared to CDC's reference values. METHODS: AK RMP involved sample hydrolysis, cholesterol extraction, and determination of cholesterol levels by spectrophotometry. The Certification Protocol for Manufacturers includes comparison with AK RMP using at least 40 fresh specimens. Demonstration of average bias ≤3% and total coefficient of variation ≤3% qualified an analytical system for certification. RESULTS: In the AK RMP used in the Osaka CRMLN laboratory, the regression equation for measuring TC was y (Osaka)=1.000x (CDC)+0.032 (n=619, R(2)=1.000). Six Japanese manufacturers had allowable performance for certification. CONCLUSIONS: The AK RMP for TC measurement was accurate, precise, and stable for 22 years. Six Japanese manufacturers were certified for 16 years.

HDL cholesterol performance using an ultracentrifugation reference measurement procedure and the designated comparison method.

BACKGROUND: Accurate high-density lipoprotein cholesterol (HDL-C) measurements are important for management of cardiovascular diseases. The US Centers for Disease Control and Prevention (CDC) and Cholesterol Reference Method Laboratory Network (CRMLN) perform ultracentrifugation (UC) reference measurement procedure (RMP) to value assign HDL-C. Japanese CRMLN laboratory (Osaka) concurrently runs UC procedure and the designated comparison method (DCM). Osaka performance of UC and DCM was examined and compared with CDC RMP. METHODS: CDC RMP involved UC, heparin-MnCl2 precipitation, and cholesterol analysis. CRMLN DCM for samples containing <200 mg/dl triglycerides involved 50-kDa dextran sulfate-MgCl2 precipitation and cholesterol determination. RESULTS: HDL-C regression equations obtained with CDC (x) and Osaka (y) were y=0.992x+0.542 (R(2)=0.996) for Osaka UC and y=1.004x-0.181 (R(2)=0.998) for DCM. Pass rates within ±1 mg/dl of the CDC target value were 91.9 and 92.1% for Osaka UC and DCM, respectively. Biases at 40 mg/dl HDL-C were +0.22 and -0.02 mg/dl for Osaka UC and DCM, respectively. CONCLUSIONS: Osaka UC and DCM were highly accurate, precise, and stable for many years, assisting manufacturers to calibrate products for clinical laboratories to accurately measure HDL-C for patients, calculate non-HDL-C, and estimate low-density lipoprotein cholesterol with the Friedewald equation.

LDL cholesterol performance of beta quantification reference measurement procedure.

BACKGROUND: Accurate measurement of blood lipids is crucial in cardiovascular disease risk management. The Centers for Disease Control and Prevention (CDC) Cholesterol Reference Method Laboratory Network (CRMLN) has assured the accuracy of these measurements for over 20 years using beta quantification (BQ) method as reference measurement procedure (RMP) for high- and low-density lipoprotein cholesterol (HDL-C, LDL-C). Only limited data exist about the performance of the BQ RMP. METHODS: Bottom fraction cholesterol (BFC), HDL-C, and LDL-C results after ultracentrifugation from the CDC lipid reference laboratory and the Japanese CRMLN laboratory were compared using 280 serum samples measured over the past 15 years. Data were compared statistically using method comparison and bias estimation analysis. RESULTS: Regression analysis between CDC (x) and Osaka (y) for BFC, HDL-C, and LDL-C were y=0.988x+1.794 (R(2)=0.997), y=0.980x+1.118 (R(2)=0.994), and y=0.987x+1.200 (R(2)=0.997), respectively. The Osaka laboratory met performance goals for 90% to 95% of the CDC reference values. CONCLUSIONS: The BQ method by the Osaka CRMLN laboratory is highly accurate and has been stable for over 15 years. Accurate measurement of BFC is critical for the determination of LDL-C.

Differences between sliding mechanics with implant anchorage and straight-pull headgear and intermaxillary elastics in adults with bimaxillary protrusion.

The aim of this retrospective study was to determine differences between the outcomes of treatment using implant anchorage compared with straight-pull headgear and intermaxillary elastics in bimaxillary protrusion patients. The lateral cephalograms of 28 adult orthodontic patients (3 males and 25 females; age, 24.9 ± 5.0 years) who had an Angle Class I malocclusion with bimaxillary protrusion were selected. Group 1 (14 patients; 1 male and 13 females; age, 25.0 ± 5.1 years) received sliding mechanics with implant anchorage and group 2 (14 patients; 2 males and 12 females; age, 24.8 ± 5.1 years) a straight-pull headgear and intermaxillary elastics. Lateral cephalometric radiographs obtained before and after treatment were traced, 13 landmarks identified, and differences in the skeletal and dental changes compared between the groups. Wilcoxon's signed-rank test was used to determine changes within the treatment groups and a Mann-Whitney U-test to evaluate significant differences. More anchorage loss occurred at the maxillary posterior teeth in group 2 (2.1 mm) than in group 1 (0.1 mm). Closing rotation of the mandible occurred in group 1, while opening rotation of the mandible was observed in group 2. These results suggest that sliding mechanics with implant anchorage may provide absolute anchorage and could control mandibular rotation more than the conventional technique.

Ten-year evaluation of homogeneous low-density lipoprotein cholesterol methods developed by Japanese manufacturers. Application of the Centers for Disease Control and Prevention/Cholesterol Reference Method Laboratory Network lipid standardization protocol.

AIM: The risk index for atherosclerotic cardiovascular diseases in the Japanese metabolic syndrome-focused health checkup program was changed from total cholesterol (TC) to low-density lipoprotein cholesterol (LDL-C). We discuss the validity of this change with respect to standardization. METHODS: The beta-quantification procedure of the Centers for Disease Control and Prevention (CDC) uses the LDL-C reference value as a target. Clinical laboratories and commercial manufacturers use homogeneous LDL-C methods for standardization. (A) For clinical laboratories, LDL-C in 648 samples requested from 108 hospitals was analyzed. (B) Manufacturers participated in the CDC/Cholesterol Reference Method Laboratory Network LDL-C standardization protocol. The standardization was conducted with a performance follow-up for the 10-year period from 1998 to 2008 at 2-year intervals, 6 times. RESULTS: (A) In clinical laboratories, acceptable LDL-C levels within ±4% of the CDC's criteria remained 70.4%, 456 of 648 subjects. Negative maximum bias deviating from the LDL-C target value was -35.8%, -52.5 mg/dL, and positive maximum bias was +24.5%, +32.3 mg/dL. (B) For manufacturers, the standardization achievement rate of the analytical reagent/instrument/calibrator system in the last four standardizations from 2002 to 2008 remained on average 66.6%, far lower than the level required. CONCLUSIONS: The standardization achievement rate of homogeneous LDL-C methods was much low-er than that of TC. TC should still be used as a risk index for atherosclerotic cardiovascular diseases. The standardization achievement rate of homogeneous LDL-C should be maintained at 100%, at least using samples with normal lipoprotein profiles. The accuracy and specificity of LDL-C should be further improved before practical and clinical use.

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.

Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage.

Recently, implant anchors such as titanium screws have been used for absolute anchorage during edgewise treatment. However, there have been few human studies reporting on the stability of implant anchors placed in the posterior region. The purpose of this study was to examine the success rates and to find the factors associated with the stability of titanium screws placed into the buccal alveolar bone of the posterior region. Fifty-one patients with malocclusions, 134 titanium screws of 3 types, and 17 miniplates were retrospectively examined in relation to clinical characteristics. The 1-year success rate of screws with 1.0-mm diameter was significantly less than that of other screws with 1.5-mm or 2.3-mm diameter or than that of miniplates. Flap surgery was associated with the patient's discomfort. A high mandibular plane angle and inflammation of peri-implant tissue after implantation were risk factors for mobility of screws. However, we could not detect a significant association between the success rate and the following variables: screw length, kind of placement surgery, immediate loading, location of implantation, age, gender, crowding of teeth, anteroposterior jaw base relationship, controlled periodontitis, and temporomandibular disorder symptoms. We concluded that the diameter of a screw of 1.0 mm or less, inflammation of the peri-implant tissue, and a high mandibular plane angle (ie, thin cortical bone), were associated with the mobility (ie, failure) of the titanium screw placed into the buccal alveolar bone of the posterior region for orthodontic anchorage.