Simultaneous quantitation of 17 endogenous adrenal corticosteroid hormones in human plasma by UHPLC-MS/MS and their application in congenital adrenal hyperplasia screening.

Accurate investigation of adrenal hormone levels plays a vital role in pediatric endocrinology for the detection of steroid-related disorders. This study aims to develop a straightforward, sensitive UHPLC-MS/MS method to quantify 17 endogenous adrenal corticosteroid hormones in human plasma. These hormones are the main ingredients in the synthetic and metabolic pathways of adrenal corticosteroid hormones. Chromatographic separation was achieved on a C18 column before electrospray ionization triple-quadrupole mass spectrometry in multiple reaction monitoring mode with a run time of 7 min. The samples were extracted by liquid-liquid extraction and required no derivatization. Analytical performance was evaluated, including linearity, analytical sensitivity, accuracy, precision, and specificity. Plasma specimens from 32 congenital adrenal hyperplasia (CAH) patients and 30 healthy volunteers were analyzed to further reveal the diagnostic value of multiple steroid hormones in the synthetic and metabolic pathways of adrenal corticosteroid in CAH diagnosis. All hormones were effectively extracted and separated using our method. The method was essentially free from potential interference of isomers or structural analogues. The imprecisions were <10%. The lower limits of quantification varied from 0.05 to 15.0 ng/ml. Good linearity coefficients (r 2 > 0.998) were also obtained for most hormones in the required concentration range, except for 21-deoxycortisol (r 2 = 0.9967) and androstenediol (r 2 = 0.9952). The recoveries for the steroid hormones ranged from 91.7 to 109.8%. We developed the UHPLC-MS/MS method for the simultaneous measurement of steroid hormones. The results showed that measurement of steroid hormones simultaneously could improve the diagnostic efficiency of CAH.

Development of human serum matrix-based unconjugated estriol-certified reference material by recommended ID-LC-MS/MS reference method.

To solve long-term lack of traceability of commercial calibrator kits and standardize clinical routine assays, we developed a human serum matrix-based unconjugated estriol (uE3) reference material (RM) with five concentration gradients. The RMs of uE3 were certified by the National Institute of Metrology (NIM) with the codes of GBW (E) 091048, GBW (E) 091049, GBW (E) 091050, GBW (E) 091051, and GBW (E) 091052. The RMs were determined by isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) reference method which was developed in our group and recommended by the Joint Committee on Traceability on Laboratory Medicine (JCTLM). GBW09224 is intended for use as a primary reference material to enable the SI-traceable measurement of uE3. This study describes the development process of these certified RMs. The candidate material was prepared by collecting from the remaining serum samples after routine clinical testing. Satisfactory homogeneity and stability were shown in these RMs. They are also commutable between the reference method and the three routine clinical immunoassay systems. To improve the accuracy of value assignment, a collaborative study in nine reference laboratories was conducted which was performed according to ISO/WD 15725-1 and all of the reference laboratories have been confirmed by China National Accreditation Service for Conformity Assessment (CNAS). The raw results were statistically analyzed and processed, coupled with uncertainty evaluation, to obtain the certified value: GBW (E) 091048 is 22.1 ± 1.3 nmol/L, GBW (E) 091049 is 33.6 ± 1.6 nmol/L, GBW (E) 091050 is 10.4 ± 0.8 nmol/L, GBW (E) 091051 is 15.5 ± 1.0 nmol/L, GBW (E) 091052 is 47.0 ± 2.0 nmol/L. The preparation process of human serum matrix-based reference material and the lack of these type of secondary (commutable) reference material of unconjugated estriol lead to the interruption of its traceability chain, which is a problem to be solved in its standardization as mentioned in the metrological traceability in ISO 17511, 2020.

A Method for Production of Human Adenosine Deaminase 1 (ADA1) in Pichia pastoris Provides Needed Quality Control Material for Clinical Laboratories.

OBJECTIVE: Adenosine deaminase (ADA) plays a major role in maintaining metabolic homeostasis via catalysis of hydrolytic deamination of adenosine to inosine. The ADA1 isoenzyme of ADA is an analyte tested in clinical laboratories; however, lack of quality control (QC) material in terms of enzyme homogeneity, stability, and coverage of the clinically relevant analytical measurement range (AMR), poses a challenge for adequate monitoring of this analyte. The aim of this study was to address the need for manufacture of QC material through recombinant expression of catalytically active ADA1 in eukaryotic cells (Pichia pastoris GS115). METHODS: The coding region of ADA1 gene was amplified by PCR and ligated into plasmid pPICZαA, followed by transfer into P. pastoris using electroporation. Recombinant ADA1 produced by P. pastoris was purified using a Ni-NTA resin column, yielding 5 mL of purified ADA1 with an activity of 4200.6 U/L. Purified ADA1 protein was added to human donor serum as the appropriate matrix for QC materials preparation. RESULTS: One hundred vials of lyophilized ADA1 were prepared at clinically significant concentrations at 41.6 U/L and 115.5 U/L (50 vials each). Both concentrations were homogenous and stable at room temperature (RT, 22-24°C) for at least 7 d, at 4°C for 3 months, and at -20°C for 12 months. Reconstituted aliquots of QC material were found to be stable at -20°C for up to 60 d and should be used within 8 h or 48 h when stored at RT or 4°C, respectively. CONCLUSION: Success of this ADA1 expression system presents a potential solution to increase production options available to clinical laboratories.

An isotope dilution liquid chromatography-tandem mass spectrometry candidate reference measurement procedure for aldosterone measurement in human plasma.

Accurate quantitation of aldosterone is clinically important in standardized testing for primary aldosteronism. The results are often variable when performed by clinical immunoassays. To standardize and ensure the accuracy of clinical systems, reference measurement procedures (RMPs) with higher metrological order are required. A simple and reliable isotope dilution LC-IDMS/MS-based measurement procedure for human plasma aldosterone has been developed. This method involved plasma spiked with a deuterium-labelled internal standard, equilibrated for 0.5 h, and extracted by liquid-liquid extraction (LLE) without derivatization. Aldosterone and its structural analogues were baseline separated with a C18-packed UHPLC column with gradient elution within 7 min. The signal intensity variability and measurement imprecision were reduced by bracketing calibration during plasma aldosterone value assignment. The limit of detection (LoD) was 19.4 pmol/L with a signal-to-noise ratio (S/N) > 3. The lowest limit of quantification (LLoQ) was 27.7 pmol/L (S/N > 10 and CV < 10.0%). LLE was performed with 1 mL of n-hexane/ethyl acetate (3:2, v/v), and the extraction recovery was determined to be 92.15 ± 3.54%. The imprecisions were ≤ 3.18% for samples at 124.8, 867.0, and 2628.5 pmol/L. The recoveries were 98.11-101.61%. The relative bias between this candidate RMP and the established RMP was 2.76-1.89%. The linearity response ranged from 27.7 to 2774.4 pmol/L with R2 = 0.999. The method performance met the requirements of RMPs (≤ 5% total CV and ≤ 3% bias). Furthermore, the developed method was applied to evaluate immunoassays through 41 patient sample comparisons. The calibration and measurement capability (CMC) of this method were also evaluated by measuring these samples. The candidate RMP can serve as an accurate reference baseline for routine methods and can be used for value assignment for reference materials. Selected ion chromatograms by LC-MS/MS using a C18 column for aldosterone and its structural analogues.

Performances Evaluation of Four Systems for Homocysteine Determination by LC-MS/MS Reference Method.

BACKGROUND: The aim of this study is to verify the analytical performance of four homocysteine detection systems made in China and to explore the comparability of homocysteine detection systems by isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) reference method. METHODS: The intra-batch precision, inter-batch precision, accuracy, and linear range of four homocysteine detection systems were evaluated. The ID-LC-MS/MS reference method was used to evaluate the comparability and accuracy of fresh frozen serum samples in four different detection systems of homocysteine. The ID-LC-MS/MS reference method is used to assign samples as calibrators to calibrate each system. The variation and deviation of fresh serum samples between different systems before and after calibration were compared. RESULTS: The intra-batch imprecision of the four detection systems was less than 5%, and the coefficient of variation of inter-batch imprecision was less than 6.7%. The precision met the clinical requirements. Before calibration, the results measured by detection system 2 are consistent with the ID-LC-MS/MS reference method, which meets the requirements of accuracy verification. The regression equation of R² ≥ 0.975 in the regression equation of linear analysis of the four systems, the linearity of the four detection systems is good in the range of evaluation concentration, and all of them can meet the declared linear range. The absolute average bias of fresh serum measured by the four detection systems after calibration decreased from 3.76 µmol/L, 0.96 µmol/L, 1.30 µmol/L, -1.56 µmol/L to 0.31 µmol/L, 0.28 µmol/L, 0.4 µmol/L, 0.40 µmol/L, respectively. The relative average bias decreased from 22.6%, 7.50%, 11.0% and -8.50% to 1.98%, 1.78%, 2.59%, 2.34%, respectively. After calibration, the slope and intercept of the regression curve of the fresh serum measured by the four detection systems and the reference method are closer to 1 and 0 than before calibration. CONCLUSIONS: The precision, reference interval, and linear evaluation of the four detection systems are good. The ID-LC-MS/MS reference method assigning fresh frozen serum samples as calibrators can improve the accuracy and comparability of the results of different detection systems.

Expression, purification and identification of isotope-labeled recombinant cystatin C protein in Escheichia coli intended for absolute quantification using isotope dilution mass spectrometry.

Isotope-labeled proteins are expected to be used as internal standard proteins in the field of protein quantification by isotope dilution mass spectrometry (ID/MS). To achieve the absolute quantification of Cystatin C (Cys C) based on ID/MS, we aims to obtain 15N isotope-labeled recombinant Cys C (15N-Cys C) protein. Firstly, the Cys C gene was optimized based on the preferred codons of Escherichia coli, and inserted into the pET-28a(+) expression plasmid. Then, the plasmid was transformed into TOP10 and BL21 strains, and 15N-Cys C was expressed in M9 medium using 15N as the only nitrogen source. 15N-Cys C was detected by SDS-PAGE, protein immunoblotting and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). The characteristic peptides obtained from 15N-Cys C were analyzed by a Q Exactive Plus MS system. Results showed that 53.06% of the codons were optimized. The codon adaptation index of the Cys C genes increased from 0.31 to 0.95, and the GC content was adjusted from 64.85% to 54.88%. The purity of 15N-Cys C was higher than 95%. MALDI-TOF MS analysis showed that the m/z of 15N-Cys C had changed from 13 449 to 14 850. The characteristic peptides showed that 619.79 m/z (M+2H)2+ was the parent ion of 15N-Cys C and that the secondary ions of 15N-labeled peptides from y+5 to y+9 were 616.27 m/z, 716.33 m/z, 788.39 m/z, 936.43 m/z, and 1052.46 m/z, respectively. In conclusion, we successfully expressed, purified and identified of 15N-Cys C protein in Escheichia coli intended for absolute quantification using ID/MS.

Determination of serum 25-hydroxyvitamin D status among population in southern China by a high accuracy LC-MS/MS method traced to reference measurement procedure.

OBJECTIVE: We aimed to describe the 25-hydroxyvitamin D (25(OH)D) status of southern Chinese individuals by a high-accuracy liquid chromatography tandem mass spectrometry (LC-MS/MS) method which can trace to reference measurement procedure. MATERIALS AND METHODS: From January 2018 to June 2019, a total of 4775 southern Chinese individuals were evaluated in our study. The serum levels of parathyroid hormone (PTH) were detected simultaneously in 162 cases. 25(OH)D was determined by LC-MS/MS, and PTH was detected using routine automated analysers. The distribution of the concentration, prevalence and seasonal variability of 25(OH)D in males and females of different age groups were studied. RESULTS: The mean 25(OH)D concentration in our study was 32.57 ng/mL (4.20-101.40 ng/mL). The global 25(OH)D concentration in males was higher than that in females of different age group. The prevalence of vitamin D deficiency (< 20 ng/mL) in females (16.65%) was higher than that in males (6.83%). The prevalence of vitamin D deficiency (< 20 ng/mL) was most common in winter (22.98% of all women and 15.49% of all men). 25(OH)D concentrations were higher in those from whom blood samples were collected in summer and autumn than in winter and spring. 25(OH)D2 was detected in 672 serum samples (14.07%). In addition, there was a negative correlation between the concentrations of 25(OH)D and serum PTH (r = - 0.149, P < 0.05). CONCLUSION: Our study demonstrated that the average serum 25(OH)D concentration in southern Chinese individuals was higher than that in other Chinese cohorts by a high-accuracy LC-MS/MS method. The global 25(OH)D concentration in males was higher than that in females of different ages, and the prevalence of vitamin D deficiency in females was higher than that in males. Seasonal change was an important aspect of 25(OH)D concentration in young and middle-aged people but became less relevant for that in older subjects. 25(OH)D2 detection was of minor practical significance in our study. In addition, we also found that there was a negative correlation between the serum levels of 25(OH)D and PTH in southern Chinese individuals.

Evaluation of a bracketing calibration-based isotope dilution liquid chromatography-tandem mass spectrometry candidate reference measurement procedure for 17α-hydroxyprogesterone in human plasma.

A candidate reference measurement procedure (RMP) based on isotope dilution coupled with liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) was developed and validated for the quantification of 17α-hydroxyprogesterone (17-OHP) in human plasma. 17-OHP spiked with a deuterium-labeled internal standard was extracted from plasma by liquid-liquid extraction with 1 mL n-hexane/ethyl acetate (3:2, v/v). Reversed-phase chromatography and positive electrospray ionization were used in the ID-LC-MS/MS. Gradient elution coupled with use of a C18-packed ultrahigh-performance liquid chromatography column allowed complete baseline resolution of 17-OHP from its structural analogue desoxycorticosterone in 6 min. To determine the 17-OHP level in human plasma, a bracketing calibration method was used to give higher accuracy and precision. The limit of detection and the lower limit of the measuring interval for the candidate RMP were 2.1 pg/mL (6.4 pmol/L) and 4.6 pg/mL (13.9 pmol/L), respectively. Extraction recovery was determined to be (96.08 ± 3.03)% (n = 3). Imprecision (intra-assay and interassay) was 4.03% or less at 0.83, 15.19, 64.22, and 313.46 ng/mL (2.51, 45.97, 194.34, and 948.56 nmol/L, respectively). Recoveries ranged from 98.05% to 102.24%. When comparing our RMP results with those obtained with an established RMP via International Federation of Clinical Chemistry and Laboratory Medicine external quality assessment scheme for reference laboratories in laboratory medicine (RELA) samples, we found that the biases ranged from -1.99% to 3.08% against the targets. No interference was observed, and the linear response ranged from 0.47 to 958.63 ng/mL (1.42 to 2900.90 nmol/L). Moreover, the candidate RMP was used to measure the concentration of 17-OHP in human plasma and was compared with an immunoassay using 40 plasma samples. The performance of the method meets the needs of an RMP (total coefficient of variation of 5% or less and bias of 3.08% or less). This method can be used for reference material value assignment of 17-OHP in human plasma matrix. It could also serve as an accurate reference baseline for routine methods to increase the accuracy and precision of certain clinical laboratory measurements. Graphical abstract Selected ion chromatograms obtained by liquid chromatography-tandem mass spectrometry with a C18 column for 17α-hydroxyprogesterone (17-OHP) from a plasma sample.

A Pre-Analytical Performance Evaluation for Measurement of Serum Creatinine in a Multicenter Clinical Trial Study.

BACKGROUND: Our multicenter clinical trial study for stage 4 chronic kidney disease (CKD) populations was conducted at 21 centers in China during the period 2011 to 2016. The CKD definition is based on glomerular filtration rate (GFR) values which can be estimated by creatinine-based predictive formulas. The validity and reliability of GFR estimation is thus largely dependent on the accurate and precise serum creatinine (SCr) measurements. As an integral part of this multicenter study, it is important to ensure the precision, accuracy, and center-to-center comparability of the SCr results. METHODS: Prior to initiating the study, we unified the measurement method of SCr determination as an enzymatic method and standardized the procedure in all of the laboratories. Then, the analytical performance of each analyzer at each laboratory was evaluated, including precision, accuracy, and comparability. RESULTS: All within-run and total CVs of the low and high level internal quality control (IQC) were comprised between 0.2% and 4.1% (< 1/3 CLIA'88). Total error of the IQC fall within the maximum 12% at all centers. The analytical bias against the Standard Reference material 967a target was less than ± 0.5% at Central Laboratory, indicating good accuracy. Correlation between the analyzers and the reference method were very high (r > 0.99). Passing-Bablok regression showed no significant deviation from linearity (p > 0.05). Bland-Altman analysis also showed good agreement (≥ 95% of results fell within the 95% limits of agreement). CONCLUSIONS: Performance evaluation helped in addressing preanalytical variations in measurement and gave op-timal quality assurance of laboratory measurement in the context of a multicenter clinical trial study.

Optimization of an enzyme-coupling method by spectrophotometer for serum adenosine deaminase: As a candidate reference method.

Adenosine deaminase (ADA) is a key enzyme of adenosine metabolism. There are currently various kits and systems available for ADA measurement, and all yield variable results. This study optimized a reference measurement procedure (RMP) for serum ADA for the standardization of routine methods. ADA coupled with purine-nucleoside-phosphorylase, xanthine-oxidase and peroxidase was selected as the basic method and was optimized using Response Surface Methodology. Then the performance was validated and the results were compared after replication by 3 other reference laboratories. A reference interval was also developed. In addition, this optimized method was applied to calibrate a routine system. The intra-assay precision was 0.44% at both concentrations of 29.8 and 100.4 U/L, and inter-assay precision was 1.01% and 0.95% at 30.1 and 100.3 U/L, respectively. The linearity was up to 351.9 U/L (R2 = 0.9998), with no significant interference or carryover (<5%). A Comparison among 4 reference laboratories showed good reproducibility (R2 ≥ 0.9975). The procedure proved valid for a reference interval of 11.7-38.5 U/L. The mean relative deviation for a routine system was -55.9% and -3.7% before and after calibration. This candidate RMP for serum ADA can potentially be used for standardization of clinical systems.

Selenepezil, a Selenium-Containing Compound, Exerts Neuroprotective Effect via Modulation of the Keap1-Nrf2-ARE Pathway and Attenuates Aß-Induced Cognitive Impairment in Vivo.

Oxidative stress is a major risk factor for neurodegenerative disease. The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2 related factor 2 (Nrf2)-antioxidant response element (ARE) pathway is one of the most potent defensive systems against oxidative stress. Selenepezil, a selenium-based compound, was previously found to exhibit excellent acetylcholinesterase (AChE) inhibition, to mimic endogenous glutathione peroxidase (GPx) activity, and to exhibit scavenging activity for hydrogen peroxide in vitro. However, none of these activities have been evaluated in a cellular model, and detailed molecular mechanisms are not elucidated. Moreover, whether selenepezil ameliorates memory deficits in vivo remains unknown. This study validated the cytoprotective effect of selenepezil against 6-hydroxydopamine (6-OHDA)- or H2O2-induced SH-SY5Y cell damage via alleviation or neutralization of intracellular microtubule disorder, reactive oxygen species (ROS) accumulation, mitochondrial dysfunction, and cell apoptosis. Our study clearly demonstrated that selenepezil pretreatment exhibited remarkable cytoprotective effect in a Nrf2-dependent manner via activating the Keap1-Nrf2-ARE pathway and stimulating the transcription of Nrf2-ARE-regulated cytoprotective genes. Moreover, selenepezil·HCl exerts neuroprotective effect via attenuating Aß-induced cognitive impairment in Alzheimer's disease (AD) rat and was more active than the reference drug donepezil. In summary, selenepezil deserves further consideration for AD therapy.

Candidate reference measurement procedure for determination of urea in serum by liquid chromatography-tandem mass spectrometry.

Urea is an important indicator of liver and kidney disease, and very frequently determined in clinical chemistry. The reference measurement procedures (RMPs) for serum urea recognized by the Joint Committee for Traceability in Laboratory Medicine are spectrophotometry, and isotope dilution (ID)-mass spectrometry (MS) coupled with gas chromatography. This study investigated a candidate RMP (cRMP) for detecting serum urea directly via ID-liquid chromatography (LC)-MS/MS, without derivatization, which simplifies pre-processing samples. The cRMP was developed and evaluated relative to the recognized RMP, inter- and intra-laboratories. The intra-precisions were 1.35%, 1.98% and 1.47% at 4.95, 24.74 and 31.36 mmol/L, respectively; inter-precision was 2.10%, 2.60% and 2.10%. The relative bias for the measurement of standard human serum (SRM 909c) was -0.49%. The relative biases were 0.41% and 0.02% for IFCC-RELA (International Federation of Clinical Chemistry and Laboratory Medicine-External Quality Assessment Scheme [EQAS] for reference laboratories) 2015A and 2015B. The linearity response between 2.4 mmol/L and 53.7 mmol/L was R2 = 0.9989. No carryover, ion suppression, or interference was detected. Correlation was acceptable with the reference spectrophotometry (R2 = 0.9985, P < 0.0001). Between our laboratory and other reference laboratories, the absolute deviation range for IFCC-RELA 2016A and 2016B was from -0.63 to 1.52 mmol/L. This well-characterized cRMP for urea can provide a base of accuracy for the traceability of clinical systems.

Interference of Thalassemias on Hemoglobin A1c Measurement by Ion-Exchange High-Performance Liquid Chromatography Method Tosoh HLC-723 G8.

BACKGROUND: The presence of hemoglobinopathies could interfere with some assays for Hemoglobin A1c (HbA1c) measurement; therefore, the effect of thalassemia on ion-exchange high-performance liquid chromatography (IEHPLC) method Tosoh HLC-723 G8 (Tosoh G8) was evaluated. METHODS: A total of 43 normal controls and 101 thalassemia patients were quantified by Premier Hb9210 and Tosoh G8 (variant-mode) systems. At the same time, 7 normal controls and 8 thalassemia patients were confirmed by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference method for verification. RESULTS: For normal controls, the HbA1c values of Tosoh G8 system (y) showed great correlation and agreement with those from Premier Hb9210 (x) (y = 0.9688x + 0.2151, r = 0.9951; mean difference 0.02 ± 0.30%), and no significant relative bias above 7% was observed; the HbA1c values obtained by Tosoh G8 were consistent with the IFCC targets (relative bias < ± 6%) in all of the samples. However, for thalassemia, the correlation between Tosoh G8 (y) and Premier Hb9210 (x) became relatively low (y = 0.8079x + 1.2897, r = 0.7780); the HbA1c values of 91.1% of the samples (92/101) obtained by Tosoh G8 were higher than those by Premier Hb9210 (mean difference 0.33 ± 0.48%) and a significant positive bias above 7% was noticed in 43.3% (45/101) thalassemia patients; when compared with the IFCC targets, the 87.5% (7/8) relative bias was > ± 6%. CONCLUSIONS: Thalassemia could directly affect the measurement of HbA1c using the IE-HPLC method Tosoh G8 and the clinical laboratorial staff should pay close attention.

Measurement of human serum unconjugated estriol without derivatization using liquid chromatography-tandem mass spectrometry candidate reference method and compared with two immunoassays.

A candidate reference measurement procedure (RMP) for measurement of unconjugated estriol in human serum has been developed and validated. The proposed method is highly reliable and uses isotope dilution coupled with liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) and requires no derivatization. An appropriate amount of serum was accurately weighed and spiked with an isotopically labeled internal standard. Unconjugated estriol and its internal standard were extracted from serum matrix using liquid-liquid extraction prior to reversed-phase LC-MS/MS. Calibrator bracketing was used to give higher specificity and accuracy for assigning serum level. The accuracy of the candidate RMP was validated by split-sample comparison to established RMPs. The lowest limit of detection (LLoD) and lowest limit of quantification (LLoQ) for developed RMP was estimated to be 0.14 nmol/L and 0.35 nmol/L, respectively. Both intra- and inter-assay imprecisions were ≤2.19% at 1.39, 17.34 and 69.35 nmol/L, respectively. Recoveries were 98.54% to 100.34% and linear response ranged from 0.35 to 173.38 nmol/L. No interference was observed. Biases were 5.6% and 2.8% against the targets of RELA2015A (3.87 nmol/L) and RELA2015B (40.62 nmol/L), respectively. Moreover, the candidate RMP was successfully applied to measure level of unconjugated estriol in serum samples of pregnant women (n = 3) and compared with two immunoassays in clinical laboratory. Our developed method is simple, accurate, and can be used as a candidate RMP to determine total unconjugated estriol level in human serum. Further improvement of certain immunoassays in accuracy and precision is needed. Graphical abstract Selected ion chromatograms by LC-MS/MS using a C18 column for uE3 from a serum sample.

Measurement of HbA1c and HbA2 by Capillarys 2 Flex Piercing HbA1c programme for simultaneous management of diabetes and screening for thalassemia.

INTRODUCTION: Thalassemia could interfere with some assays for haemoglobin A1c (HbA1c) measurement, therefore, it is useful to be able to screen for thalassemia while measuring HbA1c. We used Capillarys 2 Flex Piercing (Capillarys 2FP) HbA1c programme to simultaneously measure HbA1c and screen for thalassemia. MATERIALS AND METHODS: Samples from 498 normal controls and 175 thalassemia patients were analysed by Capillarys 2FP HbA1c programme (Sebia, France). For method comparison, HbA1c was quantified by Premier Hb9210 (Trinity Biotech, Ireland) in 98 thalassaemia patients samples. For verification, HbA1c from eight thalassaemia patients was confirmed by IFCC reference method. RESULTS: Among 98 thalassaemia samples, Capillarys 2FP did not provide an HbA1c result in three samples with HbH due to the overlapping of HbBart's with HbA1c fraction; for the remaining 95 thalassaemia samples, Bland-Altman plot showed 0.00 ± 0.35% absolute bias between two systems, and a significant positive bias above 7% was observed only in two HbH samples. The HbA1c values obtained by Capillarys 2FP were consistent with the IFCC targets (relative bias below ± 6%) in all of the eight samples tested by both methods. For screening samples with alpha (α-) thalassaemia silent/trait or beta (ß-) thalassemia trait, the optimal HbA2 cut-off values were ≤ 2.2% and > 2.8%, respectively. CONCLUSIONS: Our results demonstrated the Capillarys 2FP HbA1c system could report an accurate HbA1c value in thalassemia silent/trait, and HbA2 value (≤ 2.2% for α-thalassaemia silent/trait and > 2.8% for ß-thalassemia trait) and abnormal bands (HbH and/or HbBart's for HbH disease, HbF for ß-thalassemia) may provide valuable information for screening.

Clinical Correlates and Reference Intervals for Cystatin C in a Han Population from Southeast China.

BACKGROUND: Cystatin C (CysC) is an endogenous filtration marker for estimation of kidney function. This study aimed to define the reference interval (RI) for serum CysC in a southeast Chinese adult population and to explore the variables that affect serum CysC levels. METHODS: 532 reference individuals (259 male, 273 female, aged 18 - 79 years) were recruited from Guangzhou, China. Multiple regression analysis (MRA) was used to investigate the association between serum CysC levels and clinical factors including age, gender, body mass index, lifestyle, and biochemistry parameters. Reference values were defined using a parametric method according to Clinical and Laboratory Standards Institute guideline (C28A3). RESULTS: The mean serum CysC levels were significantly lower in females than in males (p < 0.001). Serum CysC levels increased with age (~0.047 mg/L increase per decade). MRA demonstrated that serum CysC levels correlated significantly with serum creatinine (Cr), high density lipoprotein (HDL-C), alkaline phosphatase (ALP), albumin (ALB), and uric acid (UA) concentrations, although their relationships were less prominent than those of gender or age. The RIs for serum CysC levels were calculated at 0.73 - 1.17 mg/L for subjects aged 18 - 49 years and at 0.73 - 1.49 mg/L for those aged 50 - 79 years. CONCLUSIONS: The RIs for serum CysC were established in a southeast Chinese population. In addition to gender and age, serum Cr, HDL-C, ALP, ALB, and UA also influenced serum CysC levels.

Rheumatoid Arthritis Fibroblast-like Synoviocyte Suppression Mediated by PTEN Involves Survivin Gene Silencing.

Survivin is a proto-oncogene biomarker known for its anti-apoptotic and cell cycle regulating properties induced by the activation of the phosphoinositide 3-kinase (PI3K)/Akt pathway. In the context of non-cancer pathology, such as rheumatoid arthritis (RA), survivin has emerged as a feature associated with severe joint damage and poor treatment response. Phosphatase and tensin homolog (PTEN) is a phosphatase antagonizing all classes of PI3K. The interplay between survivin oncogenic mechanisms and proliferation suppression networks in RA has remained largely elusive. This study investigated the effect of PTEN on survivin gene expression in rheumatiod arthritis fibroblast-like synoviocyte (RA-FLS). We showed for the first time that the suppression of RA-FLS was mediated by PTEN involving survivin silencing. Considering that survivin suppressants are currently available in clinical trials and clinical use, their effects in RA-FLS support a probably RA therapy to clinical practice.

Simultaneous quantitation of endogenous estrone, 17ß-estradiol, and estriol in human serum by isotope-dilution liquid chromatography-tandem mass spectrometry for clinical laboratory applications.

Estrogen measurements are important in the assessment of female reproductive function and have expanding roles in other fields. A simple, accurate, highly sensitive and specific isotope-dilution liquid chromatography-tandem mass spectrometry method was developed and evaluated to simultaneously measure three endogenous estrogens in serum: estrone (E1), 17ß-estradiol (E2), and estriol (E3). Chromatographic separation was achieved on a C18 column before electrospray ionization triple-quadrupole mass spectrometry in multiple reaction monitoring mode. The sample preparation in this assay requires no derivatization and extraction by liquid-liquid extraction. After optimization of the extraction conditions, the final extraction efficiency of E1, E2, and E3 was 83.8%, 78.9%, and 77.3% respectively. The metabolites and structural analogs that have the same molecular masses as the estrogens were separated under the optimized liquid chromatography conditions. Method validation showed satisfactory linearity over the concentration range of 20-10000 pg mL-1 for all three estrogens (r 2 > 0.997). The limits of quantification were 5, 10, and 10 pg mL-1 for E1, E2, and E3 respectively, and their recoveries ranged from 94.7% to 103.5%. The accuracy of the proposed method was further evaluated with use of certified reference materials BCR-576, BCR-577, and BCR-578 for E2 and 2014 International Federation of Clinical Chemistry and Laboratory Medicine External Quality Assessment Scheme for Reference Laboratories in Laboratory Medicine samples for E3, whose certified values were determined by reference methods. Great agreement was observed between the measured values and the certified values. Satisfactory precision (coefficients of variation less than 7.44%) was also obtained for the three estrogens. Moreover, the proposed method was successfully applied to measure the three estrogens in serum samples of pregnant women in the second trimester and to assess the accuracy of chemiluminescent immunoassays in clinical laboratories by determination of E2 and unconjugated E3 in serum samples. Graphical Abstract Schematic representation of the simultaneous quantitation of three major endogenous estrogens in human serum by ID-LC-MS/MS.

Identification of haemoglobin New York by haemoglobin A1c measurement using the Sebia Capillarys 2 Flex Piercing system.

Haemoglobinopathies may interfere with the haemoglobin A1c (HbA1c) measurement, leading to incorrect diagnosis and inappropriate treatment. It is essential that HbA1c assays are capable of identifying haemoglobinopathies. We report two cases of haemoglobin New York (HbNY) discovered through HbA1c analysis using capillary electrophoresis (Capillarys 2 Flex Piercing [C2FP], Sebia). We used these samples to evaluate the ability of three other HbA1c assays to identify this variant: ion-exchange high-performance liquid chromatography (Variant II Turbo [VII-T], Bio-Rad); boronate affinity high-performance liquid chromatography (Ultra2, Trinity Biotech) and immunoassay (Cobas c501 Tina-quant Generation 3, Roche Diagnostics). Each method was used for HbA1c assay of in samples from two cases of heterozygous haemoglobinopathy: ß0-thalassemia/HbNY (Case 1) and HbA/NY (Case 2). Only the C2FP system detected HbNY (an additional peak appeared between HbA1c and HbA0). Clinical laboratories should be aware of the limitations of their HbA1c assay methods especially in geographic areas, where haemoglobinopathy prevalence is high.

A comparative evaluation of the analytical performances of Capillarys 2 Flex Piercing, Tosoh HLC-723 G8, Premier Hb9210, and Roche Cobas c501 Tina-quant Gen 2 analyzers for HbA1c determination.

INTRODUCTION: Haemoglobin A1c (HbA1c) is widely used in the management of diabetes. Therefore, the reliability and comparability among different analytical methods for its detection have become very important. MATERIALS AND METHODS: A comparative evaluation of the analytical performances (precision, linearity, accuracy, method comparison, and interferences including bilirubin, triglyceride, cholesterol, labile HbA1c (LA1c), vitamin C, aspirin, fetal haemoglobin (HbF), and haemoglobin E (Hb E)) were performed on Capillarys 2 Flex Piercing (Capillarys 2FP) (Sebia, France), Tosoh HLC-723 G8 (Tosoh G8) (Tosoh, Japan), Premier Hb9210 (Trinity Biotech, Ireland) and Roche Cobas c501 (Roche c501) (Roche Diagnostics, Germany). RESULTS: A good precision was shown at both low and high HbA1c levels on all four systems, with all individual CVs below 2% (IFCC units) or 1.5% (NGSP units). Linearity analysis for each analyzer had achieved a good correlation coefficient (R2 > 0.99) over the entire range tested. The analytical bias of the four systems against the IFCC targets was less than ± 6% (NGSP units), indicating a good accuracy. Method comparison showed a great correlation and agreement between methods. Very high levels of triglycerides and cholesterol (≥ 15.28 and ≥ 8.72 mmol/L, respectively) led to falsely low HbA1c concentrations on Roche c501. Elevated HbF induced false HbA1c detection on Capillarys 2FP (> 10%), Tosoh G8 (> 30%), Premier Hb9210 (> 15%), and Roche c501 (> 5%). On Tosoh G8, HbE induced an extra peak on chromatogram, and significantly lower results were reported. CONCLUSIONS: The four HbA1c methods commonly used with commercial analyzers showed a good reliability and comparability, although some interference may falsely alter the result.