Inductively Coupled Plasma Mass Spectrometry as a Reference Method to Evaluate Serum Calcium Measurement Bias and the Commutability of Processed Materials during Routine Measurements / 中华医学杂志(英文版)

<p><b>Background</b>Measuring total serum calcium is important for the diagnosis of diseases. Currently, results from commercial kits for calcium measurement are variable. Generally, the performance of serum calcium measurements is monitored by external quality assessment (EQA) or proficiency testing schemes. However, the commutability of the EQA samples and calibrators is often unknown, which limits the effectiveness of EQA schemes. The aim of this study was to evaluate the bias of serum calcium measurements and the commutability of processed materials.</p><p><b>Methods</b>Inductively coupled plasma mass spectrometry was applied as a comparative method, and 14 routine methods were chosen as test methods. Forty-eight serum samples from individual patients and 25 processed materials were quantified. A scatter plot was generated from patient samples, and 95% prediction intervals were calculated to evaluate the commutability of the processed materials and measurement bias at three concentration levels was used to determine the accuracy of routine assays.</p><p><b>Results</b>All assays showed high precision (total coefficient of variation [CV] <2.26%) and correlation coefficients (r > 0.99). For all assays, the mean bias for the 48 patient samples ranged from -0.13 mmol/L to 0.00 mmol/L (-5.61-0.01%), and the ranges for the three concentrations were -0.10-0.04 mmol/L (-5.71-2.35%), -0.14--0.01 mmol/L (-5.80--0.30%), and -0.19-0.04 mmol/L (-6.24-1.22%). The EQA samples, calibrators, and animal sera exhibited matrix effects in some assays; human serum pools were commutable in all assays; certificate reference materials were commutable in most assays, and only GBW09152 exhibited a matrix effect in one assay; and aqueous reference materials exhibited matrix effects in most assays.</p><p><b>Conclusions</b>Biases for most assays were within the acceptable range, although the accuracy of some assays needs improvement. Human serum pools prepared from patient samples were commutable, and the other tested materials exhibited a matrix effect.</p>

Investigation and Analysis of Hemoglobin A1c Measurement Systems' Performance for 135 Laboratories in China / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Hemoglobin A1c (HbA1c) measurement is of great value for the diagnosis and monitoring of diabetes. Many manufacturers have developed various experiments to determine the HbA1c concentration. However, the longitudinal use of these tests requires strict quality management. This study aimed to analyze the quality of HbA1c measurement systems in China using six sigma techniques to help improve their performances.</p><p><b>METHODS</b>A total of 135 laboratories were involved in this investigation in 2015. Bias values and coefficients of variation were collected from an HbA1c trueness verification external quality assessment program and an internal quality control program organized by the National Center of Clinical Laboratories in China. The sigma (σ) values and the quality goal index (QGI) were used to evaluate the performances of different groups, which were divided according to principles and instruments.</p><p><b>RESULTS</b>The majority of participants (88, 65.2%) were scored as "improvement needed (σ < 3)", suggesting that the laboratories needed to improve their measurement performance. Only 8.2% (11/135) of the laboratories were scored as "world class (σ ≥ 6)". Among all the 88 laboratories whose σ values were below 3, 52 (59.1%) and 23 (26.1%) laboratories needed to improve measurement precision (QGI <8.0) and trueness (QGI >1.2), respectively; the remaining laboratories (13, 14.8%) needed to improve both measurement precision and trueness. In addition, 16.1% (5/31) and 15.0% (3/20) of the laboratories in "TOSOH" and "ARKRAY" groups, respectively, were scored as "world class", whereas none of the laboratories in "BIO-RAD" group were scored as "world class".</p><p><b>CONCLUSIONS</b>This study indicated that, although participating laboratories were laboratories with better performance in China, the performances were still unsatisfactory. Actions should be taken to improve HbA1c measurement performance before we can include HbA1c assays in diabetes diagnosis in China.</p>

Clinical application of real time-polymerase chain reaction in determining cytomegalovirus viral DNA load in renal transplant recipients / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Cytomegalovirus (CMV) remains a significant clinical problem among immunosuppressed renal transplant patients. Quantitative PCR assays have become the most common methods in the determination of CMV infections in transplant patients. This study was to determine the relationship between CMV infection and the acute rejection of the transplanted kidney.</p><p><b>METHODS</b>Plasma samples from 77 renal transplant patients that were pre-transplant negative for CMV infection were tested using real-time quantitative PCR and CMV gene-specific primers. The detected viral loads were retrospectively compared with the acute rejection rate and the chronic or mild rejection rates of the renal transplant.</p><p><b>RESULTS</b>CMV-DNA was detected in 29 of 77 recipients, yielding a positive rate of detection of 37.7% for this procedure. Twelve of the 21 recipients (57.1%) who suffered acute rejection had positive CMV-DNA. Among the 56 recipients suffered from chronic or mild rejection, 17 (30.4%) had positive CMV-DNA plasma. Moreover, of the 29 recipients who had detectable CMV-DNA after transplant, 12 (41.4%) suffered from acute rejection; of the 48 recipients with undetectable CMV-DNA, only nine (18.8%) developed acute rejection. Post-transplant patients with acute rejection had a higher rate (57.1% vs. 30.4%, P = 0.03) of post-transplant CMV infection than those with chronic or mild rejection.</p><p><b>CONCLUSION</b>CMV infection is a risk factor of acute renal transplant rejection and CMV infection should be prevented and treated in renal transplant recipients.</p>

Cloning of human uracil N-glycosylase and its detection in cancer tissues by quantitative RT-PCR / 生物工程学报

The uracil in DNA comes from either the misincorporation of dUTP in place of dTTP or deamination of cytosine. In the latter case, it can result in a GC to AT transition mutation if the uracil is not removed before DNA replication. Base excision repair (BER) is a major pathway for removing DNA lesions arising from endogenous processes as well as those induced by exposure to exogenous chemicals or irradiation. BER is initiated by DNA glycosylases that excise aberrant bases from DNA by cleavage of the N-glycosidic bond linking to the base of its deoxyribose sugar. Uracil N-glycosylase (UNG) is the enzyme responsible for the first step in the BER pathway that specifically removes uracil from DNA. The UNG gene undergoes both temporal and spatial regulation mainly at the level of transcription. Normally cancer cells undergo over-proliferation and up-regulate their UNG during tumorigenesis. In this study we examine the correlation between UNG level and carcinogenesis, and explore the possibility of using UNG as a marker for cancer diagnosis. Human UNG gene was amplified from the total RNA of the human choriocarcinoma cell line, JEG-3, by RT-PCR. After purification, the 942bp full-length UNG cDNA coding sequence was digested with EcoR I and Sal I, and cloned into the digested pET-21 to construct a recombinant vector, pUNG. The UNG protein was expressed under the control of T7 promoter in E. coli BL21 (DE3) cells induced with IPTG. After ultrasonic treatment, the cell lysate and precipitate were analyzed by SDS-PAGE and a 39kD band was detected. The plasmid was serially diluted at appropriate concentrations and employed as standards in the subsequent quantification. Total RNAs were extracted from 18 pairs of clinical samples, each pair contains a sample of esophageal squamous cell carcinoma (ESCC) tissue and its surrounding normal esophageal epithelia. The copy numbers of UNG mRNA in these RNA samples were determined by real-time quantitative RT-PCR using a Lightcycler (Roche). UNG was present in 13 cases of ESCC (13/18, n = 18) but absent in all of the normal tissues. The results indicated that there was a correlation between high level of UNG expression and the carcinogenesis of ESCC.

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

Objective To develop a method for the determination of total cholesterol in serum by isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS).Methods Serum samples were supplemented by addition of [3,4-~(13)C_2]-cholesterol,hydrolyzed with alcoholic sodium hydroxide and oxidized into cholest-4-ene-3,6-dione by chromic acid.The oxidation products were analyzed by LC/MS/MS using atmospheric pressure chemical ionization (APCI) source and detection modes of multiple reaction monitoring (MRM) and single ion recording (SIR).Signals (peak areas) of the internal standard were corrected for the contributions of cholesterol and the signal ratios of cholesterol to internal standard for the calibrations were linearly regressed against cholesterol concentrations.The resulted regression equation was used for the calculation of serum cholesterol concentrations.Results The correlation coefficients between the peak area ratios and cholesterol concentrations were 0.999 9 and higher.Under MRM mode,the average within-run CV of the results obtained on 3 serum samples was 0.95% (ranged from 0.92% to 0.99%) and the total CVwas 0.86% (0.82% to 0.89%),and under SIR mode,the within-run CV was 0.64% (from 0.54% to 0.77%) and the total CVwas O.69% (0.62% to 0.81%),respectively. Results on certified reference materials (SRM 1951 a Level Ⅰ and Level Ⅱ;GBW 09145 and GBW 09147) showed an average bias of 0.23% (0.14% to 1.00%) under MRM mode,and 0.24% (0.07% to 1.27%) under SIR mode.Conclusions An ID-LC/MS/MS method for serum cholesterol has been developed.It is specific and precise and may be used as a candidate reference method.

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.

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

Objective To develop a candidate reference method for the measurement of progesterone in human serum.Methods The serum sample is mixed with the internal standard [3,4-~(13)C_2] progesterone.After extraction with n-hexane and purified by a aqueous solution of 2-Hydroxypropyl-?- cyclodextrin (HP-?-CD),the serum progesterone and labeled progesterone are converted to the 3-enol heptafluorobutyrate and analyzed by gas chromatography mass spectrometry (GC/MS) with selected ion monitoring.The concentration of serum progesterone is calculated by bracketing method.Results The results gave coefficients of variation (CVs) of 0.69% to 2.12%.The analytical recoveries ranged from 98.3% to 100.1%.The results of measuring certified reference materials of serum progesterone are agree with the target value.Conclusion The procedure for measuring progesterone in serum is a highly accurate and precise method and may be used as a candidate reference method for serum progesterone assays.