The preparation and evaluation of CRP trueness verificator: homogeneity, stability and commutability / 中华检验医学杂志

Objective To prepare the trueness verification materials of C-reactive protein (CRP) and evaluate its homogeneity, stability and commutability. Methods The high and low CRP concentrations trueness verification materials were from patient leftover sera which were pooled, mixed thoroughly, filtered and aliquoted. The homogeneity, stability and commutability of these materials were evaluated according to CNAS(China National Accreditation Service for Conformity Assessment, CNAS)-GL29:2010 "Reference materials-General and statistical principles for certification (ISO Guide35:2006)"and the Clinical and Laboratory Standards Institute (CLSI) EP30A. The trueness verification materials were used to evaluate the commutability in 10 clinical CRP detection systems, using forty-five patients' leftover sera with different CRP concentration evaluated by Deming regression in EP30A of CLSI. Meanwhile, the commutability of dilution series of ERM DA-474/IFCC were evaluated using the same method. Results A total of two CRP concentration level trueness verification materials were prepared, with high and low concentration levels of 754 and 743 vials, 1 ml each, respectively. The preparation showed good homogeneity (F<F0.05(14,30);On the condition of room temperature, 2-8 ℃ and -80 ℃, these materials were stable for 7 days and 44 months respectively, the slope of the linear equation of | b1 | less than t0.95,n-2 · s(b1), there was no statistically significant difference between the slope and zero, the stability is satisfied. The materials and the dilution series of ERM-DA 474/IFCC also showed good commutability among patient sera in 10 systems. Conclusions The trueness verification materials of C-reactive protein (CRP) showed good homogeneity, stability and commutability. The dilution series ERM DA-474/IFCC also have good commutability. These provided experimental support for the value transfer and application of the trueness verification materials .

Improve the consistency of C-reactive protein test results using trueness control material / 中华检验医学杂志

Objective To explore the CRP harmonization by calibration using commutable trueness verification materials. Methods High and low level of CRP concentrations trueness verification materials(H and L) were prepared by Beijing center for clinical laboratories. Thesetrueness verification materials were diluted to 5 calibration points(5L, 4L+1H, 3L+2H, 1L+4H, 5H) by weighing method, respectively. These 5 points were used to calibrate four different brands of CRP detection system (Diasys, Leadman, Siemens and Roche) instead of the original procedure. Sera from 21 patients and the international standard ERM DA-474/IFCC were used to compare harmonization and trueness after calibration. Each sample above was measured twice. Results After calibration, the median of CV was reduced from 19.33％ to 2.92％ among 21 patient samples, less than the optimal CV based on biological variability (CV=10.6％). Compared with Desai, the slopes were closer to 1 from 0.90-1.09 to 0.93-0.96 after calibration. Meanwhile, if ERM-DA474/IFCC was used as the trueness verification materials, the absolute bias wasreduced from 3.08-11.07 mg/L to 0.52-2.97 mg/L which was close to theuncertainty of itself (2.5 mg/L). Conclusions Afterthe calibration which contained five linear concentration points of CRP trueness verification materials by weighing method, both harmonization and trueness of CRP were improved.

The value transfer and application for CRP trueness verification materials / 中华检验医学杂志

Objective To value C-reactive protein ( CRP ) trueness verification materials and to perform the CRP trueness verification program in Beijing .Methods The CRP value of trueness verification materials were assigned by the international reference material ERM DA-474/IFCC, using 10 clinical routine detection systems at departments of clinical laboratory of Beijing Chaoyang and Luhe Hospital Affiliated to Capital Medical University .The calibration curves with 4 ERM DA-474/IFCC dilutions were established and used for value transfer for trueness verification materials of two levels .The uncertainty was also assessed during the process.Then, the trueness verification was performed in the EQA at Beijing Center for Clinical Laboratories ( BCCL ) among 42 clinical laboratories.The samples were distributed according to BCCL standard operating procedure .The Microsoft Excel 2007 and SPSS 17.0 were used to process the results and the function of efficiency ( En) was calculated to verify the difference between the value and the overall mean of all participating laboratories .Results The values and uncertainties of two trueness verification materials of CRP were (109.9 ±9.4) mg/L and (27.1 ±2.4) mg/L respectively.The results of trial application of two level trueness verification materials in the EQA at Beijing Center for Clinical Laboratories (BCCL) were satisfied.There were no significant difference between the transfer values from our study and the values from means of all laboratories in Beijing .The function of efficiency ( En ) was less than 1.Conclusions The valueswhich were established by using multiple detection platforms for CRP trueness verification materialswere accurate and the uncertainties were small .This method is a preferably method for CRP value assignment because there was no suitable reference method for CRP measurement till now .Thematerialswere suitable for the trueness verification program for clinical laboratories in Beijing .

Selection and evaluation of calibrators for the conventional measurement system of serum α-Amylase / 临床检验杂志

Objective To select the calibrator for the conventional measurement system of serum a-Amylase (Amy).Methods The Amy levels of forty frozen serum samples were detected by the IFCC reference method (reference system),the conventional system A which used the Bioassay routine reagent and Randox calibrator,and was calibrated by the Roche PNPG7 method,and the conventional system B which used the Bioassay routine reagent and Randox calibrator,and was calibrated by the Rondox liquid stable PNPG7 method,respectively,and the acceptability of the two conventional systems was evaluated.Results The regression equations of the measurement values between the IFCC reference method and the conventional systems A and B were Y =0.964X +0.376 and Y =1.095X + 3.131,respectively.Among them,X and Y represented the results of the IFCC reference method and the conventional system,respectively.Compared with the IFCC reference method,the results of the conventional system A was reliable.Condusion With the guidance of the IFCC reference method,the domestic biochemical reagents matched with the suitable calibrators may provide the acceptable results.

The establishment of a method for serum glycated albumin based on liquid chromatography/tandem mass spectrometry / 中华检验医学杂志

Objective To establish a candidate reference method for determination of serum glycated albumin based on isotope dilution liquid chromatography /tandem mass spectrometry(ID-LC/MS). Methods Establishment of a method.According to the Japan Society of Clinical Chemistry(JSCC) reference method,the serum albumin was firstly purified by SDS-PAGE and decomposed into amino acid fragments.It selected 2H and 13C respectively as internal standards of lysine and DOF-lysine and chose the lysine and DOF-Lysine as standard material.Then the lysine and DOF-lysine were determined according to peak area after the optimization of analysis conditions.The validity of reference method was verified by the glycated albumin standard material JCCRM611-1 of Japan check medical material institutions.The evaluation of precision depended on the determination of three different concentrations of mixed serum samples for three days.The patients'serum(35 specimens)were determined by this method and a routine test method, and then the correlation of measured value was confirmed.Results The total CV of JCCRM611-1 reference material were 3.2%,2.3% and 2.6%, which had the bias of +2.25%, +2.38%, -1.21% by the deviation values.The intra CV was 0.33%-2.53%,CV for between -run assays was 0.83%-1.32%,total CV ranged from 2.27% to 3.2%.Correlation coefficient of the mass spectrometry and routine enzymatic method is 0.993.Conclusions The ID-LC/MS method for the measurement of serum glycated albumin is precise and accurate.In addition,this method showed great correlation with routine enzymatic method.It can be proposed as a candidate reference method for the determination of serum glycated albumin in China.

It is necessary to quickly establish the reference method and the traceability cyctem for GA in China / 中华检验医学杂志

Diagnosis and treatment of diabetes mellitus depend on accurate monitor of blood glucose of laboratory.Glycated albumin,the short-term indicator of blood glucose control, has special advantage and role in the monitor of diabetes mellitus and has been payed more and more attention.The standardization work of determination of glycated albumin at home and abroad is still in the primary stage at present.The consistency and accuracy of measurement results for glycated albumin is needed to be solved urgently.

Preparation of candidate reference materials for potassium in frozen human mixed serum / 中华检验医学杂志

Objective To prepare the candidate reference materials for frozen mixed serum potassium, in order to calibrate and evaluate the conventional methods to achieve mutual recognition of the results.Methods Fresh sera without hemolysis,lipemia and choloplania were collected.Serum pools were packed in the freezing tube in the 1 000 (1 ml/per).Use the Single Factor Analysis of Variance(ANOVA) to evaluate the homogeneity.The short-and long-term stability [(2 -8℃,room temperature,37 ℃) and long-term (-80 ℃ ) ] were investigatedby linear regression analysis.The value was assigned by transfer from NIST SRM-956c using reference method by ICP-MS and uncertain was calculated.We observed the commutability of 25 fresh patient serum samples and 3 levels candidate RMs between reference method and three analyzed systems.The candidate RMs( refernce materials) were then distributed to 33 laboratories in Beijing to apply in routine assay by using different detection systems.Results By statistical analysis of the SPSS 17 statistical software, the F value of homogeneity test of each level candidate RMs was 0.247, 0.117, 0.162.All of them were less than F0.05 (9,20) =2.39;Stability can be last at least 12 months,30 days, 12 days and 4 days at -80 ℃, 2-8℃, room temperature and 37℃respectively.The definited values of three levels candidate RMs for potassium were (2.349 ±0.028) mol/L,(3.845 ±0.024) mol/Land (5.831 ±0.042)mol/L;Coordinate dots of 3 levels candidate RMs are all within 95% confidence interval range of 25 serums regression line.They have the same speciality as serum.In correctness verification survey of 33 clinical laboratory of conventional methods,97%bias in results The biases of 97%RMs were within the range of ±2.5%( ±1/2 CLIA′88Tea).Conclusion The homogeneity, stability and commutability of 3 levels candidate RMs all meet the requirement and the target values are assigned accurately.

The preparation of human serum based reference materials for alpha-fetoprotein assay through quantity value transmission from multiple analysis systems / 中华检验医学杂志

Objective To prepare the frozen human serum pools for AFP reference materials through quantity value transmission from several analysis systems . Methods Method establishment. According to the requirement of preparation for the national standard materials , the studies of homogeneity and stability of frozen human serum pools for AFP reference materials were carried out .The commutability of prepared AFP reference materials and WHO AFP 72/225 reference material were assessed .By use of four automated chemiluminescence analysis systems , the prepared reference materials and different dilutions of WHO reference material 72/225 were tested in the same run.The values of prepared AFP reference materials were assigned by comparing these results and the uncertainty was evaluated .Results The three levels of AFP reference materials were tested to be homogeneous .The long term stability had been observed at -80℃for 14 months.The different dilutions of WHO AFP 72/225 reference material and three levels of prepared reference materials were commutable with patient serum samples among the four analysis systems .Through multiple system quantity value transmission and total uncertainty evaluation , the assigned values ( IU/ml) of three levels of AFP reference materials were 23.0 ±3.0, 93.2 ±7.2, ( 26.1 ±2.4 ) ×102 respectively.Conclusions The three levels of AFP reference materials were homogeneous and stable in accordance with requirement of preparation for national standard materials .The assigned values were reliable.The materials showed accepted commutability across 4 analytical systems.These materials had been approved as the national certified reference materials .These reference materials could be applied for the calibration or calibration verification of clinical analytical systems and the external quality assessment schemes for clinical laboratories.

Preparation of the mixed serum calibrators for C-reactive protein / 中华检验医学杂志

Objective To prepare serum calibrators for CRP measurement.Methods Fresh serum without infectious diseases , hemolysis, lipemia and choloplania were collected and divided into 3 groups, low, medium, and high, according to the CRP concentration.Each serum pool was mixed , filtered, sterilized and aliquoted.The materials were tested for homogeneity and stability.The values of the CRP was assigned by particle enhanced immunonephelpmetry , and calibrated with international reference materials.The expanded uncertainty was evaluated.Results The materials were tested to be homogeneous (Ubb﹤Ur, P>0.05) with Ubb values being 0, 0.125, 0, Ur values being 0.046, 0.213, 0.785, and F values being 0.803, 1.686, 0.966 in CL, CM, CH groups respectively.Stability study, where F values are 0.609, 0.259, and 1.557 at 22-25℃, 1.217, 4.583, and 0.893 at 2-8℃(P>0.05), showed that the materials were stable for at least 3 days at 22-25 ℃or 30 days at 2-8 ℃, respectively.The certified values of the 3 levels materials for CRP were ( 2.64 ±0.14 ) , ( 31.17 ±0.63 ) , ( 73.85 ±1.74 ) mg/L, respectively.Conclusion The calibrators prepared for serum CRP measurement were homogeneous , stable and accurately assigned and can be used to calibrate the CRP measure system.

The determination of potassium in human serum by isotope dilution inductively coupled with plasma mass spectrometry / 中华检验医学杂志

Objective To establish a method for the determination of serum potassium using isotope dilution inductively coupled plasma mass spectrometry.Methods Frozen human serum pools of different potassium concentrations were prepared from healthy donors of Chao-yang Hospital laboratory in 2010 Serum samples were diluted with 1％ HNO3 supplemented with 41K spike and isotope ratio was measured after selection and optimization of ICP-MS analysis conditions.Serum 39K concentrations were calculated by interpolation method.3 different serum samples were used to evaluate the precision of the method.Standard Reference Material 909b Ⅰ and Ⅱ of National Institute of Standards and Technology were used to evaluate the accuracy.The recovery was evaluated through 2 serum samples added standard material for potassium,uncertainty was calculated.Results The analytical precision of serum potassium measurement was 0.14％ to 0.11％.The results of SRM909b Ⅰ and Ⅱ gave the coefficients of variation (CVs) of 0.39％ to 0.32％.Data was consistent with the certified value and the CV was + 0.12％ and + 0.49％ respectively.The recovery was 99.68％ to 100.12％ for 2 different serum samples.Conclusions ID-ICP-MS method was successfully established to measure the serum potassium concerntration precisely and accurately,it is an ideal method for the accurate determination of inorganic elements.

Determination of glycated hemoglobin standardization situation / 中华检验医学杂志

Glycated hemoglobin is internationally recognized as the gold standard for assessment of long-term glycemic status in diabetic patients,but our determination of glycosylated hemoglobin standardization work is still at primary stage at present.Consistency and accuracy of glycated hemoglobin results are still needed to be solved.

Measurement of serum calcium by flame atomic absorption spectrometry: validation of a candidate reference method / 中华检验医学杂志

Objective To investigate the measurement of serum calcium by flame atomic absorption spectrometry (FAAS) and to validate the method for use as a candidate reference method. Methods Serum was diluted by 50 fold with 50 mmol/L hydrochloric acid containing 10 mmol/L LaCl3 and analyzed for calcium on an AA 6800 atomic absorption spectrophotometer. Dilution solutions and FAAS conditions were optimized and the performance of the method was evaluated. Results The method showed within-run, between-run and total CVs of 0. 31%～0.38%, 0.16%～0.30% and 0.35%～0.49%, respectively, and analytical recoveries ranging 98.9%～101.1%. No significant interferences were detected. Conclusions A FAAS method for the measurement of serum calcium has been established. The method is simple and accurate and may be used as a candidate reference method for serum calcium.