The consistency of aminotransferase analysis in China: a comparison of six mainstream aminotransferase routine methods and recalibration using human pooled serum preparations supplemented with human recombinant aminotransferases.

Background: To evaluate the consistency of six mainstream homogeneous systems for aminotransferase measurements and improve the consistency of measurements by applying uniform calibrators.Methods: 200 individual samples were grouped into four sets for assays with and without pyridoxal-5-phosphate (P-5'-P) for Alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Routine assays for the P-5'-P group were compared with a reference measurement procedure (RMP). In the non-P-5'-P group, four routine assays were analyzed in a pairwise method across six method pairs. Recalibration was performed using human serum pools (HSPs) supplemented with human original recombinant aminotransferases (HOR). Data were analyzed by Passing-Bablok regression and Bland-Altman plots.Results: In the P-5'-P group, the mean biases for Ortho and Dimension assays for ALT were 17.0% and -25.4%, respectively; for AST, the mean biases were -9.5% and -9.6%, respectively. In the non-P-5'-P group, the mean deviations ranged from -5.9% to 5.9% for ALT. For AST, the relative deviations ranged from -19.1% to 6.5%. After recalibration, in the P-5'-P group, the relative biases were reduced to -12.2% to 7.7% for ALT and -6.9% to 0.8% for AST. The mean deviations for the non-P-5'-P AST group were reduced remarkably (-3.0% to 3.3%).Conclusion: Assays supplemented with P-5'-P exhibited poor performance against RMP for both ALT and AST. For assays without P-5'-P, AST results showed non-satisfactory comparability for almost all method pairs. Uniform calibrators such as HSPs supplemented with HOR could improve consistency among the mainstream homogeneous systems for the measurement of aminotransferase activity, particularly for AST measurement.

Passively Q-switched Tm:YAP laser with a lead zirconate titanate saturable absorber.

In the paper, we prepare a lead zirconate titanate saturable absorber, which is used to demonstrate a passively Q-switched (PQS) Tm:YAP laser. In the PQS mode, an average output power of 0.81 W and pulse width of 1.69 µs at 175 kHz are obtained at 1991.9 nm with a pump power of 12.76 W, corresponding to an optical-optical conversion efficiency of 6.35%. In addition, the beam quality factors M2 of the PQS Tm:YAP laser in the x and y directions are 1.17 and 1.15, respectively.

Preparation, stability and commutability of candidate reference materials for lactate dehydrogenase (LDH).

BACKGROUND: Lactate dehydrogenase (LDH) is a key enzyme that functions as a marker of cell damage. Its activity can be measured by a variety of laboratory methods. To eliminate inter-method bias and enhance equivalence among different measurement procedures, LDH detection needs to be standardized. METHODS: Optimized sequences coding for lactate dehydrogenase subunit A (LDH-A) and subunit B (LDH-B) were synthesized and cloned into the pRSFDuet vector, and then the constructed 6His-LDHA-pRSFDuet, 6His-LDHB-pRSFDuet, and 6His-LDHA-LDHB-pRSFDuet plasmids were transformed into Escherichia coli BL21 (DE3) for expression. The enzyme activity and specific activity of recombinant LDHs were detected. Electrophoresis of LDH isoenzymes was performed. The stability of recombinant LDHs and serum LDH was evaluated. Commutability of recombinant LDH-B was studied by the IFCC reference method and six routine methods. RESULTS: Three plasmids were constructed and three highly concentrated recombinant LDH isoenzymes were obtained. The specific activities of LDH-A, LDH-AB, and LDH-B were 18.08 U/mg, 21.74 U/mg, and 14.18 U/mg, respectively. There was a desirable linear correlation between the activities of recombinant LDH isoenzymes and their protein concentrations. Electrophoresis of LDH isoenzymes showed that the recombinant LDH-B corresponded to LDH1 and it demonstrated good stability at 4 °C and 25 °C for 5 weeks. LDH-B formulations in saline-bovine serum albumin solution and human serum matrix were commutable for six routine methods. CONCLUSION: Human recombinant LDH-B has great potential to become an improved and less expensive standard or reference material in external quality assessment for clinical LDH measurement.

Predictive Hydration Model of Portland Cement and Its Main Minerals Based on Dissolution Theory and Water Diffusion Theory.

Efficient and accurate cement hydration simulation is an important issue for predicting and analyzing concrete's performance evolution. A large number of models have been proposed to describe cement hydration. Some models can simulate the test results with high accuracy by constructing reasonable functions, but they are based on mathematical regression and lack of physical background and prediction ability. Other models, such as the famous HYMOSTRUC model and CEMHYD3D model, can predict the hydration rate and microstructure evolution of cement based on its initial microstructure. However, this kind of prediction model also has some limitations, such as the inability to fully consider the properties of cement slurry, or being too complicated for use in finite element analysis (FEA). In this study, the hydration mechanisms of the main minerals in Portland cement (PC) are expounded, and the corresponding hydration model is built. Firstly, a modified particle hydration model of tricalcium silicate (C3S) and alite is proposed based on the moisture diffusion theory and the calcium silicate hydrate (C-S-H) barrier layer hypothesis, which can predict the hydration degree of C3S and alite throughout the age. Taking the hydration model of C3S as a reference, the hydration model of dicalcium silicate (C2S) is established, and the synergistic hydration effect of C3S and C2S is calibrated by analyzing the published test results. The hydration model of tricalcium aluminate(C3A)-gypsum system is then designed by combining the theory of dissolution and diffusion. This model can reflect the hydration characteristics of C3A in different stages, and quantify the response of the hydration process of C3A to different gypsum content, water-cement ratio, and particle size distribution. Finally, several correction coefficients are introduced into the hydration model of the main mineral, to consider the synergistic hydration effect among the minerals to some extent and realize the prediction of the hydration of PC.

Commutability Assessment of Candidate External Quality Assessment Materials for Aminotransferase Activity Measurements Based on Different Approaches in China.

BACKGROUND: Using commutable external quality assessment (EQA) materials is important for monitoring successful harmonization efforts. We assessed the commutability of four human serum pool (HSP) preparations to identify candidate EQA materials for alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity measurement. METHODS: One set each of 85 clinical samples (CSs) was collected for ALT and AST activity measurement. The 15 candidate EQA materials included four types of HSP preparations (A to D): materials A, C, and D contained human original recombinant (HOR) aminotransferases; materials B was mixed leftover samples. The CSs and 15 candidate EQA materials were analyzed using seven routine assays, and the ln-transformed results were analyzed in 21 assay pairs. Commutability was assessed using Deming regression, with a 95% prediction interval (CLSI approach) and the difference in bias with an error component model (International Federation of Clinical Chemistry and Laboratory Medicine [IFCC] approach). RESULTS: For ALT, all materials were commutable for 14-21 assay pairs according to the CLSI and IFCC approaches. For AST, B01-03 showed commutability for 14-21 assay pairs, and C01-03 and D01-03 showed commutability for no less than 10 assay pairs according to the two approaches. A01-06 were commutable for 9-16 assay pairs according to the CLSI approach, but for 6-9 assay pairs according to the IFCC approach. CONCLUSIONS: Mixed leftover samples showed desirable commutability characteristics as candidate EQA materials for routine aminotransferase activity measurements. Human serum bases supplemented with HOR were commutable for most routine ALT activity measurements.

Investigation on Hydration and Mechanical Properties of Mortar Containing Limestone Powder and Fly Ash Based on the Coupled Chemical-Thermal-Mechanical Method.

The composited cementitious materials usually have superior performance; for example, using limestone powder (LP) and fly ash (FA) as the admixtures of cement in concrete/mortar is a popular way of improving the properties of concrete/mortar structures. In this work, we performed experimental tests to study the hydration process and pore distribution in mortar containing different ratios of LP and FA. Based on the results of mercury intrusion porosimetry (MIP), a numerical mortar model with random pore is built. The model can reflect the synergistic hydration interaction and filling effect caused by the admixtures of LP and FA. After analyzing the hydration process, the coupled chemical-thermal-mechanical method was used to simulate the characteristics of mortar containing LP and FA. The coupling model can simulate the "hump-type" hydration acceleration stage of the mortar at early age, which is specifically caused by the LP, proved in the experimental test. Additionally, the special, "hump-type" stage is important to enhance the early strength of the mortar. At different levels of admixture content, the random pore model and coupled method can predict the evolution process of the mechanical properties well, at early age and for long-term strength. Both experimental and numerical results suggest that the mortar containing admixtures of the proper ratio of LP to FA have good mechanical properties, which can be applied to engineering structures.

Commutability of control materials for external quality assessment of serum apolipoprotein A-I measurement.

BACKGROUND: The aim of the current study was to evaluate the commutability of commercial control materials and human serum pools and to investigate the suitability of the materials for the external quality assessment (EQA) of serum apolipoprotein A-I (apo A-I) measurement. METHODS: The Clinical and Laboratory Standards Institute (CLSI) EP14-A3 protocol was used for the commutability study. Apo A-I concentrations in two levels of commercial control materials used in EQA program, two fresh-frozen human serum pools (FSPs) and two frozen human serum pools prepared from residual clinical specimens (RSPs) were measured along with 50 individual samples using nine commercial assays. Measurement results of the 50 individual samples obtained with different assays were pairwise analyzed by Deming regression, and 95% prediction intervals (PIs) were calculated. The commutability of the processed materials was evaluated by comparing the measurement results of the materials with the limits of the PIs. RESULTS: The FSP-1 was commutable for all the 36 assay pairs, and FSP-2 was commutable for 30 pairs; RSP-1 and RSP-2 showed commutability for 27/36 and 22/36 assay pairs, respectively, whereas the two EQA materials were commutable only for 4/36 and 5/36 assay pairs, respectively. CONCLUSIONS: Non-commutability of the tested EQA materials has been observed among current apo A-I assays. EQA programs need either to take into account the commutability-related biases in the interpretation of the EQA results or to use more commutable materials. Frozen human serum pools were commutable for most of the assays.