After the relationship between glycemic control and the HbA1c concentration was demonstrated, many tests have been developed to determine the HbA1c concentration. The test results are standardized to the International Federation of Clinical Chemistry (IFCC) Reference Measurement Procedure (RMP) in harmony with the efforts of the National Glycohemoglobin Standardization Program (NGSP). The longitudinal use of the test requires strict quality management including accreditation of the laboratory, a dedicated internal control design, participation in an external quality assessment (EQA) program (proficiency test), and careful consideration of pre- and post-analytical aspects of the test. Performance goals for optimizing determination of the HbA1c concentration have been described. As an index of long-term glycemic control and a risk predictor, the HbA1c concentration is an indispensable part of routine management of diabetes. Because of the improving quality of the test, the HbA1c concentration is being increasingly applied in the diagnosis of diabetes. There are, however, concerns of this application in point-of-care settings. The HbA1c concentration is also used to achieve stringent control in pregnant diabetic patients. Strict standardization enables the definition of universal reference values and clinical decision limits. This review describes the present status of analytical and clinical aspects of determining the HbA1c concentration and highlights the challenges involved.
Diabetes Mellitus/blood/diagnosis ; Hemoglobin A, Glycosylated/*analysis/standards ; Humans ; Immunoassay/standards ; Point-of-Care Systems ; Quality Control

BACKGROUND: Due to the westernization of living environments in Korea, a number of allergy patients are greatly increasing. External quality control assessments are difficult for allergy tests due to the lack of reference methods. We surveyed the current status of allergy tests performed in medical laboratories in Korea to prepare for an external quality control assessment in the near future. METHODS: We conducted a survey on internal and external quality control trials, calibrations and its intervals, medical staffs, analyzers in use, an average number of tests per months, and report formats. RESULTS: Among the 85 laboratories surveyed, 61 were doing allergy tests including 6 reference laboratories. There were two different types of analyzers (1) qualitative or semi-quantitative and (2) quantitative. These analyzers use either chemiluminescent or immunoblot method. Fifty-five laboratories were using 'qualitative or semi-quantitative' analyzers as a screening test and 31 laboratories were using quantitative analyzers. Most of the laboratories were only doing an internal quality control assessment included in the test kits. Excepting a few laboratories, calibrations were not done. About 34 laboratories reported numerical values with interpretative reports prepared by laboratory medical doctors. CONCLUSIONS: The necessity of external quality control assessment has become an issue for improving the quality of allergy tests. But due to the lack of standardization, it is difficult to carry out external quality control assessments. By grouping the laboratories in terms of the type of analyzers, we could overcome the problem of analyzer variations and launch an external quality control assessment program in the near future.
Allergens/*immunology ; Chemiluminescent Measurements/standards ; Humans ; Immunoassay/instrumentation/*standards ; Immunoblotting/standards ; Immunoglobulin E/*blood/immunology ; Korea ; Quality Control

No abstract available.
*Algorithms ; Automation ; Clinical Laboratory Information Systems/*standards ; Humans ; Immunoassay/*methods ; Indicator Dilution Techniques ; alpha-Fetoproteins/*analysis

Performance of the electrochemiluminescent immunoassay system of Elecsys 2010 was evaluated by quantitative assay. The functional sensitivity of the TSH assay was 0.004 microU/ml. The extra-assay imprecision was RSD = 1.45%-4.65% in the range of TSH concentrations of 0.43-88.15 microU/ml. The intra-assay imprecision was RSD = 1.38%-3.14% in the range of TSH concentrations of 0.41-87.28 microU/ml. The recovery of TSH was in the range of 98.6%-104.4%. The correlation between theoretical values and obtained values of TSH was adequate(r = 0.999). We conclude that the Elecsys 2010 is provably satisfactory in sensitivity, precision, accuracy, reliability, practicability and rapidity.
Electrochemistry ; instrumentation ; Evaluation Studies as Topic ; Humans ; Immunoassay ; instrumentation ; standards ; Luminescent Measurements ; Sensitivity and Specificity ; Thyrotropin ; blood

In 2010, the Japan Diabetes Society decided to introduce the National Glycohemoglobin Standardization Program (NGSP) values into clinical practice. Accordingly, NGSP Certification of Japanese manufacturers of HbA(1c)-related diagnostic reagents and instruments was initiated in February, 2012, through an NGSP network laboratory, the Asian Secondary Reference Laboratory (ASRL) #1. Traceability to the NGSP reference system can be endorsed by manufacturer certification, as well as by the College of American Pathologists (CAP) survey. Nevertheless, only a few manufacturers participate in the CAP survey in Japan. Thus, proficiency testing (PT) was proposed and executed by ASRL #1. Single-donor whole-blood samples were used for the PT. The participated measurement systems were NGSP certified. Twenty-two laboratories obtained certification through ASRL #1; 2 through the Secondary Reference Laboratory (SRL) #8; and 9 through the SRL #9. The combination plots of the bias data in this PT and in the NGSP certification performed in March and May in 2012 were consistent with each other: mean NGSP values at each level agreed well with the target value. In conclusion, PT using whole blood is useful in endorsing NGSP certification.
Asia ; Chromatography, High Pressure Liquid ; Enzyme Assays ; Hemoglobin A, Glycosylated/*analysis/standards ; Humans ; Immunoassay ; Japan ; Laboratory Proficiency Testing/*standards ; Quality Control ; Reference Standards ; Republic of Korea ; Societies, Scientific

BACKGROUND: Establishment of trimester- and assay-specific reference intervals for every population is recommended. The aim of this study was to establish a trimester- and assay-specific reference interval for thyroid-stimulating hormone (TSH) and free thyroxine (FT4) in Korean pregnant women. METHODS: From April 2012 to December 2012, 531 pregnant women receiving prenatal care and 238 age-matched, non-pregnant women were enrolled in this study. After excluding patients with pregnancy-associated complications or thyroid-specific autoantibody, 465 pregnant and 206 non-pregnant women were included. Non-parametric analysis (2.5-97.5th percentile) was performed to determine the reference interval. Levels of TSH and FT4 were determined by electrochemiluminescence immunoassay (Elecsys thyroid tests, Roche Diagnostics, Germany). RESULTS: The TSH reference intervals were 0.01-4.10, 0.01-4.26, and 0.15-4.57 mIU/L for the first, second, and third trimester, respectively. From the first trimester to the third trimester, the median TSH levels showed a significantly increasing trend (P<0.0001). The FT4 reference intervals were 0.83-1.65, 0.71-1.22, and 0.65-1.13 ng/dL for the first, second, and third trimester, respectively, showing a significantly decreasing trend (P<0.0001). CONCLUSIONS: Establishing trimester-specific reference intervals in pregnant women is essential for accurate assessment of thyroid function. Our population-specific and method-specific reference intervals will be useful for screening Korean pregnant women for thyroid disease.
Adult ; Asian Continental Ancestry Group ; Case-Control Studies ; Female ; Humans ; *Immunoassay/standards ; Luminescent Measurements ; Pregnancy ; Pregnancy Trimesters ; Prenatal Care ; Reference Values ; Republic of Korea ; Thyroid Hormones/*analysis/standards ; Thyroxine/*analysis/standards

BACKGROUND: Fibrin-related markers (FRM) such as fibrin monomer (FM) and D-dimer (DD) are considered useful biological markers for the diagnosis of disseminated intravascular coagulation (DIC). However, no studies on the diagnostic performance of different FRMs have been published in Korea. The aim of this study was to evaluate the diagnostic performance of FM for DIC in comparison with DD. METHODS: The reference limit of FM was determined based on plasma sample data obtained from 210 control individuals. To evaluate diagnostic performance, FM data from the plasma samples of 139 patients with DIC-associated diseases were obtained for DIC scoring. FM was measured by immunoturbidimetry using STA-LIATEST FM (Diagnostica Stago, France). Patients were classified according to the DIC score as non-DIC, non-overt DIC, or overt DIC. ROC curve analyses were performed. RESULTS: The reference limit in the control individuals was determined to be 7.80 microg/mL. Patients with DIC-associated diseases were categorized as non-DIC (N=43), non-overt DIC (N=80), and overt DIC (N=16). ROC curve analyses showed that the diagnostic performance of FM was comparable to DD in both non-overt DIC and overt DIC (P=0.596 and 0.553, respectively). In addition, FM had higher sensitivity, specificity, positive predictive value, and negative predictive value than DD for differentiating overt DIC from non-DIC. CONCLUSIONS: This study demonstrated that the diagnostic performance of FM for DIC was comparable to DD. FM might be more sensitive and more specific than DD in the diagnosis of overt DIC, but not non-overt DIC.
Area Under Curve ; Biological Markers/blood ; Disseminated Intravascular Coagulation/blood/*diagnosis ; Fibrin Fibrinogen Degradation Products/*analysis/immunology/standards ; Humans ; Immunoassay/*methods/standards ; Nephelometry and Turbidimetry/*methods/standards ; ROC Curve ; Reagent Kits, Diagnostic ; Reference Values

BACKGROUND: Fibrin-related markers (FRM) such as fibrin monomer (FM) and D-dimer (DD) are considered useful biological markers for the diagnosis of disseminated intravascular coagulation (DIC). However, no studies on the diagnostic performance of different FRMs have been published in Korea. The aim of this study was to evaluate the diagnostic performance of FM for DIC in comparison with DD. METHODS: The reference limit of FM was determined based on plasma sample data obtained from 210 control individuals. To evaluate diagnostic performance, FM data from the plasma samples of 139 patients with DIC-associated diseases were obtained for DIC scoring. FM was measured by immunoturbidimetry using STA-LIATEST FM (Diagnostica Stago, France). Patients were classified according to the DIC score as non-DIC, non-overt DIC, or overt DIC. ROC curve analyses were performed. RESULTS: The reference limit in the control individuals was determined to be 7.80 microg/mL. Patients with DIC-associated diseases were categorized as non-DIC (N=43), non-overt DIC (N=80), and overt DIC (N=16). ROC curve analyses showed that the diagnostic performance of FM was comparable to DD in both non-overt DIC and overt DIC (P=0.596 and 0.553, respectively). In addition, FM had higher sensitivity, specificity, positive predictive value, and negative predictive value than DD for differentiating overt DIC from non-DIC. CONCLUSIONS: This study demonstrated that the diagnostic performance of FM for DIC was comparable to DD. FM might be more sensitive and more specific than DD in the diagnosis of overt DIC, but not non-overt DIC.
Area Under Curve ; Biological Markers/blood ; Disseminated Intravascular Coagulation/blood/*diagnosis ; Fibrin Fibrinogen Degradation Products/*analysis/immunology/standards ; Humans ; Immunoassay/*methods/standards ; Nephelometry and Turbidimetry/*methods/standards ; ROC Curve ; Reagent Kits, Diagnostic ; Reference Values

BACKGROUND: The importance and usefulness of therapeutic drug monitoring (TDM) have been emphasized, and analysis of drugs has been increased in clinical laboratories. We evaluated the analytical performance and clinical usefulness of a recently introduced enzyme multiplied immunoassay instrument, Viva-E Drug Testing System (Dade Behring Inc., USA). METHODS: Using patients' samples and quality control material, we evaluated the analytical performance of Viva-E for a total of 11 drugs (cyclosporine, tacrolimus, mycophenolic acid, valproic acid, digoxin, theophylline, carbamazepine, phenytoin, phenobarbital, vancomycin, and gentamicin) with respect to linearity, precision, and correlations with other methods according to CLSI guidelines. Cobas Integra 800 (Roche Diagnostics, Switzerland) and API 4000 LC-MS/MS System (Applied Biosystems, USA) were used to make a comparison. In addition, we analyzed analysis time. RESULTS: Viva-E showed a good linearity (r2 > or = 0.97) for all items. Within-run CVs were within 5% and total CVs were within 10% for all drugs except for tacrolimus and digoxin at low concentrations. The system correlated well with the other methods (r=0.9283-0.9778). The time required for reporting the first sample was 11 min and the analysis time was 1.1 min. CONCLUSIONS: Since Viva-E showed a good analytical performance required for TDM in its linearity, precision, and accuracy with its wide drug menus including cyclosporine, tacrolimus, and mycophenolic acid, stat and random accessing functions, and the consolidation to a single workstation, it could be very useful in the clinical laboratory for various needs.
Data Interpretation, Statistical ; Drug Monitoring/*instrumentation/methods ; Enzyme Multiplied Immunoassay Technique/*instrumentation ; Humans ; Immunoenzyme Techniques ; Pharmaceutical Preparations/*analysis ; Quality Control ; Reference Standards ; Reproducibility of Results

Amyloid β (Aβ) peptides are important components of plaques in patients with Alzheimer's disease (AD). Recent studies suggest that a low plasma ratio of Aβ42 to Aβ40 may precede the development of the sporadic form of AD. The aim of this study was to establish reference intervals for plasma Aβ in Korean adults. A total of 370 apparently healthy individuals (181 males and 189 females aged 40-69 yr) without cognitive impairment were enrolled. Plasma concentrations of Aβ40 and Aβ42 were measured by using a human amyloid β assay kit (Immuno-Biological Laboratories, Japan). Reference intervals were established according to the "CLSI guidelines for defining, establishing, and verifying reference intervals in the clinical laboratory". There was no need to partition the data with respect to gender or age group. The 95th percentile reference intervals for Aβ40 and Aβ42 were 127-331 pg/mL and 2.31-19.84 pg/mL, respectively. The reference interval for the Aβ42/Aβ40 ratio was 0.011-0.092. Plasma Aβ concentrations obtained in this study could be used as reference intervals for clinical purposes.
Adult ; Aged ; Alzheimer Disease/blood ; Amyloid beta-Peptides/*blood/standards ; Asian Continental Ancestry Group ; Biomarkers/blood ; Female ; Healthy Volunteers ; Humans ; Immunoassay/standards ; Male ; Middle Aged ; Reference Values ; Republic of Korea