Common reference intervals for aspartate aminotransferase (AST), alanine aminotransferase (ALT) and γ-glutamyl transferase (GGT) in serum: results from an IFCC multicenter study.

BACKGROUND: Aspartate aminotransferase (AST), alanine aminotransferase (ALT) and γ-glutamyl transferase (GGT) measurements are important for the assessment of liver damage. The aim of this study was to define the reference intervals (RIs) for these enzymes in adults, paying attention to standardization of the methods used and careful selection of the reference population. METHODS: AST, ALT and GGT were measured with commercial analytical systems standardized to the IFCC-recommended reference measurement systems. Three centers (two in Italy and one in China) measured their own freshly collected samples; one of these centers also measured frozen samples from the Nordic Countries RI Project and from a Turkish center. RIs were generated using non-parametric techniques from the results of 765 individuals (411 females and 354 males, 18-85 years old) selected on the basis of the results of other laboratory tests and a specific questionnaire. RESULTS: AST results from the four regions (Milan, Beijing, Bursa and Nordic Countries) were statistically different, but these differences were too small to be clinically relevant. Likewise, differences between the upper reference limits for genders was only 1.7 U/L (0.03 µkat/L), allowing a single RI of 11-34 U/L (0.18-0.57 µkat/L) to be defined. Interregional differences were not statistically significant for ALT, but partitioning was required due to significant gender differences. RIs for ALT were 8-41 U/L (0.13-0.68 µkat/L) for females and 9-59 U/L (0.15-0.99 µkat/L) for males, respectively. The upper reference limits for GGT from the Nordic Country population were higher than those from the other three regions and results from this group were excluded from final calculations. The GGT RIs were 6-40 U/L (0.11-0.66 µkat/L) for females and 12-68 U/L (0.20- 1.13 µkat/L) for males, respectively. CONCLUSIONS: For AST and ALT, the implementation of common RIs appears to be possible, because no differences between regions were observed. However, a common RI for GGT that is applicable worldwide appears unlikely due to differences among populations.

Reference intervals for ALT, AST, GGT and LDH among the Han Chinese in Beijing area / 中华检验医学杂志

ObjectiveTo establish the reference intervals for ALT,AST,GGT and LDH among the Han nationality in Beijing.MethodsThe document C28-P3 issued by CLSI was a guideline about how to define,establish,and verify reference intervals in the clinical laboratory.IFCC had established multicenter enzymes reference intervals based on the guideline.Exclusion criteria were designed for screening candidate reference individual according to the document C28-P3 and the multicenter study's experience.Blood specimens were collected from 315 healthy individuals aged 20 to 60 years old,including 132 males and 183 females.Reference materials were used to ensure the accuracy of the test results of the four liver enzymes.The methods which used to test the four liver enzymes could be traced to the IFCC enzymes reference measure procedure,the reagent of ALT and AST included pyridoxal phosphate.Results There was statistically difference between males and females of the referenceranges forALT, ASTand GGT.Therefore,gender-specific reference intervals were established as ALT:8.2 -50.8 U/L (F),12.7 -71.8 U/L (M) ; AST:15.0 -36.7 U/L ( F),16.6 -51.1 U/L (M) ;GGT:9.0 -37.3 U/L (F),12.0 -50.9 U/L (M).For LDH,the reference interval was 127 -224 U/L,as no significant gender difference was found.ConclusionsThe reference intervals for the four liver enzymes based on the population of the Han nationality in Beijing are established.The upper reference limit for ALT in Beijing Han population is higher than that from other similar studies.

Preanalytical and intraindividual biological variations of 19 biochemistry analytes / 中华检验医学杂志

Objective To investigate preanalytical and intraindividual biological variations of 19 biochemistry analytes. Methods For the study of preanalytical variations, 10 consecutive blood specimens were taken from each of 21 individuals and the specimens were taken from different arms and with various evacuated blood tubes and venous occlusion durations and processed with different storages before and after centrifugal separation of serum. Another 3 aliquots of blood, each at an interval of 1 week, were taken from the individuals for the study of intraindividual biological variations. All the serum samples were analyzed in duplicate for 19 biochemistry analytes. Analysis of variance was performed on the results for the estimation of preanalytical and biological variations. Results Various preanalytical treatments or factors caused some systematic variations but random specimen errors were the main contributors of preanalytical variations. Chloride, sodium and calcium showed preanalytical variations of less than 1% and other analytes ranging from 1%-7%. Different analytes showed varied intraindividual biological variations. The least biological variations ( <2% ) were observed on chloride, sodium and calcium and the largest ( >20% ) on bilirubin,triglycerides, alanine aminotransferase and creafine kinase. Conclusions Preanalytical variations under laboratory settings in China and intraindividual biological variations in Chinese for 19 biochemistry analytes have been estimated. These data will be useful in the estimation of measurement uncertainty and the interpretation of clinical laboratory results.

Determination of serum glucose by isotope dilution liquid chromatography tandem mass spectrometry / 中华检验医学杂志

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.

Establishment and implementation of reference systems in laboratory medicine / 中华检验医学杂志

Good patient care requires accurate and comparable laboratory test results. To achieve standardization, a reference system consisting of a hierarchal framework of validated and reliable analytical methods linked by reference materials must be in place. Supported by national and municipal research programs, construction of reference systems has been pursued and progress been made. Candidate reference methods have been set up or developed for some important tests, and the methods have been used in the calibration or evaluation of routine methods, study of commutability of control materials and characterization of reference materials. Phenomenal roles of reference systems are expected in diagnostic reagent manufacturing, internal quality assurance and external quality assessments.

Determination of sodium in serum by inductively coupled plasma mass spectrometry / 中华检验医学杂志

Objective To develop a candidate reference method for the determination of sodium in serum by inductively coupled plasma mass spectrometry method (ICP-MS). Methods Aluminum, as internal standard of sodium, was added into serum samples and sodium standard solutions by gravimetric analysis. The samples were digested by HNO3 and diluted, and its 23Na/27Al isotope ratios were obtained by ICP-MS. The sodium concentrations were calculated with the standard curve method in serum. Results The analytical recoveries of sodium were 100.67% and 100.15% respectively, and the precisions were 0.08% and 0.04% respectively for 2 different serum samples. The results of measuring sodium in serum of Standard Reference Material (SRM) gave the coefficients of variation (CVs) of 0.18% and 0.22% for 2 levels of standard reference material(SRM) 909b and 0.41%, 0.41% and 0.66% for 3 levels of SRM 956b. The relative deviations between the results and median of the certified value were 0.17% and 0.14% for 909b and -0.09%, -1.05%, -0.48% for 956b respectively. Conclusions The ICP-MS and aluminum internal standard method is proved to be not only precise and accurate, but also quick and convenient for measuring sodium in serum. It is promising to be a candidate reference method for determination of sodium in serum.

Determination of serum creatinine by isotope dilution liquid chromatography tandem mass spectrometry: a candidate reference method / 中华检验医学杂志

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.

Roles of reference method in clinical biochemistry / 中华检验医学杂志

Roles of reference method in clinical biochemistry were introduced.Reference method is an important component of the reference system.Reference methods are primarily used for the establishment and assurance of the traceability of measurement results through calibrating and evaluating routine methods and assigning values to reference materials.Calibration biases and non-specificities of routine methods and the commutability of reference materials are the major issues in the standardization of clinical biochemistry.Standardization also requires availability of commutable reference materials.Reference methods are irreplaceable tools to identify the issues and to characterize reference materials.

Determination and metrological traceability of glycated hemoglobin / 中华检验医学杂志

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.

Determination of serum urea by isotope dilution gas chromatography mass spectrometry:a candidate reference method / 中华检验医学杂志

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.

Determination of serum total glycerol by isotope dilution liquid chromatography tandem mass spectrometry / 中华检验医学杂志

Objective To develop a method for measuring serum total glycerol by isotope dilution (ID)liquid chromatography tandem mass spectrometry(LC/MS/MS).Methods Serum samples were mixed with [13C3]-glycerol(internal standard)and treated with alcoholic potassium hydroxide to hydrolyze serum glycerides to glycerol.The natural glycerol and the internal standard were benzoylated with the Schotten-Baumann reaction and the benzoates were analyzed by LC/MS/MS.Results The correlation coefficients between the peak area ratios and glycerol concentrations were 0.999 9 and higher.The withinrun coefficients of variation(CV)for serum total glycerol analysis averaged 0.94%(ranged 0.21%～2.62%)and the total CV 1.15%(0.62%～2.00%).Results on certified reference materials(SRM 909b Level Ⅰ and LevelⅡ;GBW 09146 and GBW 09147)showed an averaged bias of 0.20%(-0.20%～1.06%).Conclusions An ID-LC/MS/MS method for serum total glycerol has been developed.The method iS highly specific and precise and may be used as a candidate reference method for serum total glycerol measurements.

Evaluation of matrix effects in serum urea measurements / 中华检验医学杂志

Objective To evaluate the matrix effects in serum urea measurements of external quality assessment(EQA)materials and commercial reference materials(calibrators or controls)on enzymatic methods and to verify the trueness of the enzymatic methods.Methods The Clinical and Laboratory Stadards Institute(CLSI)EP 14-A2 protocol was used for the evaluation of matrix effect.An isotope dilution gas chromatography mass spectrometry method was used as the comparative method.Twenty five fresh patient serum samples,15 EQA materials and 13 calibrators or controls were analyzed with 7 enzymatic methods (evaluated methods)and the comparative method and results were processed according to the protocol. The trueness of the evaluated methods were also assessed by comparing the fresh sample results obtained with the evaluated and comparative methods.Results Eight of 15 EQA materials and 3 of 13 calibrators or controls showed no matrix effects on all the 7 routine methods.One processed sample showed matrix effect on all the routine methods.Method dependent matrix effects of other materials were observed on other materials.Calibration biases were also observed on some enzymatic methods.Conclusions Matrix effects and calibration bias have been observed in serum urea measurements.Continued efforts are needed for improving the accuracy and the comparability of serum urea measurements.

Performance of IFCC enzyme reference method laboratory network in China / 中华检验医学杂志

Objective To review the performance of the IFCC enzyme reference methods in China laboratories and to evaluate the competence of enzyme reference measurement in China.Methods The Intemational Federation of Clinical Chemistry and Laboratory Medicine(IFCC)enzyme reference methods were performed in 8 China laboratories.Reference procedures were developed by each laboratory and the performances were evaluated.The Clinical and Laboratory Stadards Institute(CLSI)EP-5 protocol was used for the evaluation of precision and certified reference materials(CRMS)were used for the verification of trueness.Seven of the 8 laboratories participated in the 2006 IFCC external quality assessment program for reference laboratories(RELA)for the assessment of the measurement performance.Results Within-run CVs of less than 1.5%and between-run CVs of less than 2%were achieved bv all the China laboratories.Results on CRMs by some of the laboratories agreed with the certified value within the stated uncertainty.In the 2006 RELA,the averages and the interlaboratory CVs of the China laboratories were similar to those of international laboratories.Conclusion A preliminary enzyme reference method laboratory network has been established in China.

The government regulation of clinical laboratory quality in China / 中华检验医学杂志

Over the past years efforts have been made by the government to improve the management of clinical laboratories.The government activities such as networking of quality assurance, development and implementation of clinical laboratory standards, and establishment of external quality control mechanisms have facilitated the improvement of clinical laboratory quality.Further definition and integration of clinical laboratory services, introduction of clinical laboratory pathologists and consultation and establishment of a permission mechanism are needed for improving the effectiveness of clinical laboratory services.Government regulations will continue to play an essential role in the clinical improvement process.

Analytical quality specifications in laboratory medicine / 中华检验医学杂志

specifications are essential for total quality management in laboratory medicine. A consensus among worldwide professionals has been achieved and a hierarchy of strategies for setting analytical quality specifications has been proposed based on their relevance to medical decision-making. Quality specifications derived from biological variations have been widely accepted because of their objectivity and practicability and have more and more been used in the quality management in laboratory medicine.

Research on whole blood control materials for lymphocyte subset counting by flow cytometry / 中华检验医学杂志

Objective To research on a whole blood control material for lymphocyte subset counting by flow cytometry(FCM).Methods To detect lymphocyte subset in whole blood with different preservers by flow cytometric multi-color analysis.Results whole blood control material for lymphocyte subset counting by FCM was prepared.In 2-8℃ refrigerator, the light scatter and CD45 of leukocytes of whole blood control were stable in 72 days. The cluster of lymphocyte, monocyte, neutrophil in plot were separated easily from debris. The lymphocyte subset of whole blood control can be counted by FSC/SSC or CD45/SSC gating. The variation of lymphocyte subset count was less in different preserving day. The coefficient of variation (CV) of lymphocyte subset count was less than 6.5% in our laboratory and less than 13% in external quality assessment among 56 laboratories in China.Conclusion The whole blood control prepared by us can be used for internal quality control and external quality assessment in lymphocyte subset counting by FCM, it is very important signification to ensure the quality and accuracy of lymphocyte subset count.

Reference system for completed blood count / 中华检验医学杂志

A reference system for the completed blood count (CBC) have been established in National Center for Clinical Laboratory (NCCL) according to the standards published by International Council for Standardization in Hematology (ICSH) and International Organization for Standardization (ISO) in order to calibrate hematology analyzer.The contents of our study mainly include:(1)Establishment of calibration laboratory for CBC, which is the first calibration laboratory accepted by China National Accreditation Board for Laboratories in all medical laboratories.(2)We firstly set up the reference method for CBC in China. In addition, the data between NCCL and a foreign reference laboratory have been compared. (3)We have calibrated some instruments from routine laboratories by the fresh blood or calibrator valuated by the reference system, which acts as a new way to calibrate hematology analyzer.(4) A secondary standard assay system has been established and the data between it and the foreign reference laboratory have been compared chronically. The experience has been introduced to local laboratories in 26 provinces.(5) We have drafted out several documents about technical standard for laboratory medicine. The main institution of applications includes: local center for clinical laboratory, clinical laboratories for routine examination, institutions for identification to instruments and reagents, centers for disease control and prevention, and so on.

Determination of serum cholesterol by isotope dilution gas chromatography mass spectrometry / 中华检验医学杂志

Objective To develop a new isotope dilution gas chromatography mass spectrometry method (ID/GC/MS) for the measurement of serum cholesterol.Methods Serum was mixed with an isotope labeled internal standard ([3,4-~(13)C]-cholesterol) and treated with alcoholic sodium hydroxide to hydrolyze cholesterol ester to cholesterol.Cholesterol and internal standard was extracted and derived by N, O-Bis(trimethylsilyl) trifluoroacetamide to trimethylsilyl ethers.The derivation products were analyzed by capillary column GC combined with electron impact MS using scan and selected ion monitor (SIM) modes. Signals of cholesterol internal standard were corrected for the contributions from cholesterol and the signal ratio of cholesterol to internal standard for the calibrators were linearly regressed against cholesterol concentrations.The resulted regression equation was used for the calculation of serum cholesterol concentrations.Results The new ID/GC/MS method showed a mean within-run coefficient variance (CV) of 0.04%-0.81%.Comparison with two levels of standard reference material (SRM1951a) of National Institute of Standards and Technology (NIST) displayed a bias of 0.19% and 0.90% respectively.Conclusion A time-gaining ID/MS method has been established that is highly precise and accurate and can be used for the measurement of serum cholesterol.