Objective To investigate the stability of glycated hemoglobin HbA1c in whole blood sample measured by Tosoh G7, Roche/Hitachi 7170A and NycoCard READER Ⅱ under different storage conditions. Methods Three whole blood samples (EDTA anticoagulated) with different glycated hemoglobin levels and one whole blood sample (heparin anticoagulated) were collected and stored at -80 ℃, -20 ℃, 4 ℃,room temperature(15 -25 ℃), and 37 ℃ HbA1c was analyzed by each method on days 1, 2, 5, 7, 9, 14, 21,28, 35, 42, 49, 56, 63 and 70 respectively. Results The results of sample stored at -80 ℃ appear to be stable for Tesoh G7 and Roche/Hitachi 7170A method. The coefficients of variation (CV) for Tosoh G7 was 0.54%-1.22%. The CV for Roche/Hitachi 7170A was 0.86% -1.82%. When samples was detected with Tosoh G7 method, the results was consistent when the sample was stored at -20 ℃ for 14 days, 4 ℃ for 63 days, room temperature for 5 days, and 37 ℃ for less than 1 day. When samples was detected with Roche/Hitachi 7170A method, the results was consistent when the samples was stored at -20 ℃ for 21 days, 4 ℃ for 42 days, room temperature for 7 days, and 37 ℃ for less than 1 day. The NycoCard READER Ⅱ showed stability at 4 ℃ for 9 days, and room temperature for less than 1 days. Conclusions The stability of whole blood samples is dependent on different methods. Storage time under different temperatures is different.

Diabetes is a worldwide epidemic disease in the twenty-first century.The most danger of diabetes is its complications which are the major cause of morbidity and mortality in diabetic patients.The development and progression of diabetes complications are directly associated with blood glucose levels,Hemoglobin A1c is not only the gold standard for the long-term blood glucose control of diabetic patients,but also the World Health Organization (WHO) recommended diagnosis of diabetes.Thus,a question has been raised:how to improve the comparability of hemoglobin A1c results meet clinical needs? At least four points should be taken in determining hemoglobin A1c:(1)Understand the interference factors; (2)Choose scientific and practical methodologies; (3)Standardized operation; (4)Regularly monitor the quality of testing results.

Objective To investigate the value of the joint detection of Troponin T(TnT),highsensitivity C-reactive protein (hs-CRP) and N-terminal probrain natriuretic peptide (NT-proBNP) for the clinical diagnosis of acute coronary syndrome(ACS) in elderly patients.Methods The adequate serum samples were collected in each group:unstable angina (UA) (49 cases),non-ST segment elevations myocardial infarction(NSTEMI) (48 cases),acute myocardial infarction(AMI) (37 cases)and healthy control (45 cases).The levels of TnT and NT-proBNP were measured by electrochemiluminescent double antibody sandwich method,and hs CRP by immune transmission turbidity.The roles of individual and joint detection of the three indicators were analyzed by ROC curve and Logistic regression model.Results Except for TnT in UA group,the serum TnT,NT-proBNP and hs-CRP levels were significantly higher in three ACS groups than in healthy control group (P＜0.05).The largest areas under the ROC curve (AUC) of individual TnT,NT-proBNP,hs-CRP testing and the joint detection for UA were 0.583±0.059,0.786±0.047,0.620±0.058 and 0.787±0.046,for NSTEMI were 0.967±0.022,0.978±0.015,0.897±0.032 and 0.991 ±0.009,for AMI were 0.971 ± 0.024,0.961 ± 0.021,0.874 ± 0.043 and 0.999 ± 0.002,therefore,the area under the ROC curve of the joint detection was increased to some degree as compared with individual TnT,NT-proBNP,hs-CRP testing.Similarly,the best sensitivity and specificity of individual TnT,NT-proBNP,hs-CRP testing and the joint detection for UA were 16.7％ and 100.0％,54.2％ and 91.1％,54.2％ and 75.6％,50％ and 95.6％; for NSTEMI were 93.5％ and 100.0％,95.7％ and 97.8％,67.4％ and 97.8％,95.7％ and 100.0％; for AMI were 94.1％ and 100.0％,91.2％ and 97.8％,67.8％ and 97.8％,100.0％ and 97.8％,respectively.Conclusions Joint detection of TnT,NT-proBNP,hs-CRP can significantly improve the diagnosis of UA; for NSTEMI and other AMI,it can be achieved the optimism of sensitivity and specificity,but its effect of distinguishing NSTEMI and AMI is little.

This article summarized recent correlative literatures focusing on international standards on glycated hemoglobin.The basic concept,determination of glycated hemoglobin,the present review in laboratory measurement and metrological traceability was introduced.The international community has established reference system and metrological traceability to the International System of Units on HbA1c.Determination in glycated hemoglobin is still in incipient stage in our country.Both clinical laboratorians awareness and clinical determination need to be strengthened.

Objective To prepare the serum reference materials for total thyroxine .Methods Individual blood samples were collected from 13 healthy donors (7 males and 6 females) aged from 20 to 50 years old, and the sera were separated and mixed into 4 serum pools according to the concentration of thyroxine.The materials were tested for homogeneity and stability using routine methods .The method of isotope dilution liquid chromatography tandem mass spectrometry ( ID-LC/MS/MS) was used to determine the concentration of thyroxine .The candidate reference materials were also measured by four conventional methods to analyze the commutability of the materials .Results It showed that the four candidate reference materials were homogeneous and commutable in four conventional methods and they were tested to be stable for at least 1 year at -70 ℃using the isochronous stability study .The certified values ( reference value ± expanded uncertainty ,nmol/L) were:75.9 ±1.8,105.3 ±2.2,114.7 ±2.1 and 187.4 ±2.9.Conclusions Certified reference materials for serum thyroxine have been prepared .These materials have been approved to be the Certificate Reference Materials of GBW 09127,GBW 09128,GBW 09129 and GBW 09130.

Objective To evaluate the commutability of certified reference materials, external quality assessment program materials and calibrators for serum glucose measurements which were performed in 24 routine measurement procedures.Methods 35 fresh patient specimens and some reference materials were analyzed by isotope dilution liquid chromatography tandem mass spectrometry ( as the comparative method) and 24 routine measurement procedures (as the evaluated methods).The relationships between the results from the evaluated method and the comparative methods were evaluated to identify the commutability.Results It showed that 5 certified reference materials, 2 trueness verification materials, and 5 calibrators were commutable in all 24 routine measurement procedures.The other samples were displayed the presence of commutability issue in different degrees.Conclusion It is important to pay more attention to the problems brought by commutability of reference materials in clinical laboratory.

Objective To develop a candidate reference method for the measurement of serum glucose based on isotope dilution liquid chromatography tandem mass spectrometry(ID-LC/MS/MS)Methods An internal standard [~(13)C_6]glucose was added to serum samples and equilibrated with endogenous glucose.Serum proteins were removed by a precipitation with anhydrous ethanol.Serum glucose and the internal standard were then reacted with 1-phenyl-3-methyl-5-pyrazolone and the formed derivatives were analyzed by liquid chromatography tandem mass spectrometry with multiple reaction monitoring(MRM).The method was calibrated with bracketing calibrators and serum glucose concentrations were calculated by comparing the peak area ratios of samples with that of the calibrators.Results The within-run,between-run and total coefficients of variation averaged 0.36%,0.47%and 0.61%,respectively.The analytical recoveries ranged from 99.0% to 100.9%.Results of analyzing the certified reference material SRM 965a showed an average biases of-0.20%.Conclusions An ID-LC/MS/MS method for measuring serum glucose has been developed.The method is highly precise and accurate and may be used as a candidate reference method.

Objective To develop a candidate reference method for the measurement of creatinine in human serum based on isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS). Methods An isotopically labeled internal standard [<'2>H<,3>] creatinine was added to the serum sample and equilibrated with the endogenous creatinine. The samples were treated with anhydrous ethanol to remove proteins by precipitation. After being washed with chloroform for further clean-up, the samples were analyzed by LC/MS/MS. Serum creatinine was quantified by a bracketing calibration. Results The within-run, between-run and total coefficients of variation ranged from 0.52% to 0.61%, 0.11% to 0.59% and 0.61% to 0.83%, and the averages were 0.57%, 0.43% and 0.73%, respectively. The analytical recoveries ranged from 99.09% to 101.13% with an average of 100.3%.The results of analyzing the certified reference material SRM 909b (Level Ⅰ and Ⅱ) and SRM 967b showed biases of less than 0.4%. Conclusions An ID-LC/MS/MS method for measuring serum creatinine has been developed. The method is highly precise and accurate and may be used as a candidate reference method for serum creatinine measurements.

Objective To develop a candidate reference method for the measurement of urea in human serum based on isotope dilution/gas chromatography/mass spectrometry.Methods [13C,15N2]Urea used as internal standard Was added to the serum sample and equilibrated with endogenous nonlabeled urea.The serum samples were treated with anhydrous ethanol to emove proteins by precipitation.The serum urea and labeled urea were converted into a trimethylsilyl derivative of 2-hydroxypyrimidine and analyzed by gas chromatography/mass spectrometry system with selected ion monitoring.The concentration of serum ureaWas calculated by the theory of bracketing method.Results The average value of within-run oefficient of vailation(CV),between-run CV and total CV of the procedure were 0.38%(ranged from 0.12%to 0.47%),O.62%(ranged form 0.49% to 0.87%)and 0.73%(ranged from 0.51% to 0.93%).Respectively.The analytical recoveries ranged from 99.37% to 100.95%.The resuhs of analyzing the certified refefence material SRM909b(Level Ⅰand Ⅱ)showed a bias less than 0.2%.Conclusion The procedure for measuring urea in serum is a highly accurate and precise method and can be used as a candidate reference method for serum urea assays.

Objective Preparation of aqueous reference materials for cholesterol and glycerol.Methods Study on reference materials.The certified reference materials GBW09203b and GBW09149 were weighed accurately and dissolved into 20% of methyl cyclodextrin aqueous solution to prepare six kinds of candidate reference materials of cholesterol and glycerol according to the concentration.The materials were tested for homogeneity and stability using routine methods.The reference methods of isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) were used to determine the concentration of cholesterol and glycerol to evaluate the accuracy of the certified values.Meanwhile, the blank verification test was carried out.The expanded uncertainty was the combination of standard uncertainty of measurement, unhomogeneity and instability.Results It showed that the six candidate reference materials were homogeneous and stable for at least 1 year at-70 ℃ and-20 ℃.The certified values (reference value ± expanded uncertainty,mmol/L) were as follows,for cholesterol:0.65±0.01,1.31 ±0.01,2.57±0.02,5.21±0.06,7.71±0.08,10.24±0.06;for glycerol:0.29±0.01,0.58±0.01,1.22±0.02,2.24±0.02,3.46±0.04,4.52 ±0.04.The results of reference methods were consistent with the certified values.Blank validation tests showed that the concentration of the analytes would not be affected by the reagent and the blank matrix.Conclusions Certified reference materials for cholesterol and glycerol in aqueous solution have been prepared successfully.These materials are homogeneous and stable, and the certified values are reliable.Therefore the materials have been approved to be the Certificate Reference Materials of GBW 09823, GBW 09824, GBW 09825, GBW09826, GBW09827 and GBW 09828.