Comparability of thyroid-stimulating hormone immunoassays using fresh frozen human sera and external quality assessment data.

BACKGROUND: This study aimed to assess the comparability among assays using freshly frozen human sera and external quality assessment (EQA) data in China. METHODS: Twenty-nine serum samples and two commercial EQA materials, obtained from the National Center for Clinical Laboratories (NCCL), were analyzed in triplicate using eight routine TSH assays. The commutability of commercial EQA materials (NCCL materials) was evaluated in accordance with the CLSI EP30-A and IFCC bias analysis. Median values obtained for the NCCL EQA materials were used to determine the systematic and commutability-related biases among immunoassays through back-calculation. The comparability of TSH measurements from a panel of clinical samples and NCCL EQA data was determined on the basis of Passing-Bablok regression. Furthermore, human serum pools were used to perform commutable EQA. RESULTS: NCCL EQA materials displayed commutability among three or five of seven assay combinations according CLSI or IFCC approach, respectively. The mean of systematic bias ranged from -13.78% to 9.85% for the eight routine TSH assays. After correcting for systematic bias, averaged commutability-related biases ranged between -42.26% and 12.19%. After correction for systematic and commutability -related biases, the slopes indicating interassay relatedness ranged from 0.801 to 1.299 using individual human sera, from 0.735 to 1.254 using NCCL EQA data, and from 0.729 to 1.115 using pooled human serum EQA(the commutable EQA). CONCLUSIONS: The harmonization of TSH measurement is challenging; hence, systematic and commutability-related biases should be determined and corrected for accurate comparisons among assays when using human individual serum and the commercial EQA materials.

Homogeneity and Stability Evaluation of External Quality Assessment Control Materials for Four Coagulation Tests.

BACKGROUND: This study assessed the homogeneity and stability of control materials used in external quality assessment (EQA) of four coagulation tests, aiming to verify that these materials meet clinical testing requirements and to provide an evidence base for future improvement of laboratory coagulation test quality. METHODS: The homogeneity and stability of control materials were assessed according to the relevant guidance. Homogeneity assessment involved 10 vials of samples obtained from 2 batches (each vial tested twice). The homogeneity of control materials in four coagulation tests was assessed using one-way analysis of variance, with standard deviation of uniformity (Ss) 0.3 σ as an assessment criterion. Stability assessment involved two vials of sam-ples obtained from two batches (each vial tested twice). The stability of control materials was assessed at cold storage, room temperature, temperature of 37°C. Reconstitution stability of control materials placed in cold storage and at room temperature, and long-term stability of reconstituted control materials stored frozen (-20°C and -80°C) were observed. Linear regression analysis was performed to assess long-term stability. RESULTS: The Ss values of EQA control materials for four coagulation tests were PT L1 Ss = 0.084, PT L2 Ss = 0.889, APTT L1 Ss = 0.164, APTT L2 Ss = 0.223, Fbg L1 Ss = 6.256, Fbg L2 Ss = 2.251, TT L1 Ss = 0.552, TT L2 Ss = 0.3111. PT, APTT, Fbg, and TT were associated with the standard deviation of uniformity values of 0.3 σ. Non-reconstituted samples were observed at 37°C for 2 hours and 4 hours, and at room temperature for 1 day. Reconstituted samples were observed when stored at 4°C for 4 hours and 8 hours, at room temperature for 4 hours, and at -20°C and -80°C for 6 months. Instability of reconstituted samples was observed in PT and APTT tests at 4°C for 8 hours and at -20°C for 5 months. CONCLUSIONS: EQA control materials presented with satisfactory homogeneity in four coagulation tests. Non-reconstituted samples presented with satisfactory stability at 37°C for 2 hours and 4 hours and at room temperature for 1 day, while reconstituted samples presented with satisfactory stability when refrigerated at 4°C for 4 hours, when kept at room temperature for 4 hours, and when frozen at -80°C for 6 months.

Trueness assessment of routine electrolytes measuring systems using the candidate reference method by ion chromatography.

Electrolytes for sodium, potassium, magnesium, and calcium are important serum ions that are frequently assayed in clinical laboratories. In this study, we assessed the trueness of routine analytical systems for four cations using an inexpensive candidate reference method aimed to promote the standardization of serum electrolyte detection. An ion chromatography (IC) method with Cesium as an internal standard was developed and evaluated. The residual clinical serum samples at Chaoyang Hospital were collected and prepared into three human serum pools of electrolytes, which were used for the trueness evaluation of five routine analytical systems. Furthermore, the agreement between routine methods and the IC method was verified using 40 individual human samples. The recovery rates of sodium, potassium, magnesium and calcium were 99.69%, 100.34%, 100.43% and 99.89%, respectively. The intra-batch standard deviation and intra-laboratory precision of NIST SRM 956c were all less than 1% for the four ions. The certified values were within the validation range, and the deviation between the results and the certified values were less than 0.5%. The three serum pools were homogeneous and stable. All routine systems aligned with the IC method for four cations and achieved the analytical quality specifications for potassium and magnesium at 3 different concentrations. The developed IC method is simple, practical, accurate, and precise, which can be used as a candidate reference method for serum electrolytes measurement. Five routine analytical systems for electrolytes measurement had the acceptable bias for potassium and magnesium and their results showed good concordance.

Spatial and vertical distribution, composition profiles, sources, and ecological risk assessment of polycyclic aromatic hydrocarbon residues in the sediments of an urban tributary: A case study of the Songgang River, Shenzhen, China.

In this study, the Songgang River (SR) was selected as a typical tributary that is heavily polluted by rapid urbanization and industrialization. The polycyclic aromatic hydrocarbon (PAH) distribution at five representative sampling sites from different urban functional areas was studied. The chemical and physical properties and spatial and vertical distribution of PAHs in sediments were investigated. PAH source identification and the ecological risks of the sediments were evaluated. The results suggested that the industrial zone and dense residential and commercial areas were the most contaminated areas of the SR, as the chemical and physical properties of total organic carbon content in sediments was the highest at the dense residential and commercial areas (0.1-4.5%); however, the acid volatile sulfide, total nitrogen, and total phosphorus contents were the highest in the industrial zone, with ranges of 700.0-1618.4 mg/kg dw, 22.4-3543.9 mg/kg dw, and 82.3-4550.7 mg/kg dw, respectively. The spatial distribution of residual PAHs in the sediment cores showed a wide variation among different urban functional areas, and the vertical characterization (0-300 cm) depicted a significant decreasing trend with depth and with an abrupt increase at 180 cm. The concentration of ∑16 PAHs ranged from 208.7 to 7709.8 ng/g dw, with the highest concentrations obtained in the industrial zone. The low molecular weight-PAHs (153-6720 ng/g dw) were predominant in the sediments. Furthermore, there were combined sources (biomass burning: 40.3%; fossil fuel combustion: 25.5%; mixed source: 21.5%; oil pollution: 12.7%) and a long term accumulation effect, with anthropogenic activities and industrial pollution as the major contributing sources. The concentrations of Nap, Acy, Ace, Flu, and Ant exceeded the lower limit of the sediment quality criteria, and higher toxic equivalent concentration values of the total carcinogenic PAHs were observed nearby the midstream of the SR, which may cause adverse biological effects and implies a need for regular monitoring.

Commutability of external quality assessment materials for point-of-care glucose testing using the Clinical and Laboratory Standards Institute and International Federation of Clinical Chemistry approaches.

OBJECTIVES: The aim of this study was to assess the commutability of three external quality assessment (EQA) materials for point-of-care (POC) glucose testing using two approaches, to identify suitable EQA materials to evaluate and monitor the quality of POC testing. METHODS: Commercial control materials (CCMs), pooled human serum samples (PHSs), and homemade human whole-blood samples (HWBs) were measured along with 33 individual clinical samples using five POC instruments and a Hitachi 7600 analyzer. Data were analyzed by Deming regression analysis with a 95% prediction interval as described in Clinical and Laboratory Standards Institute (CLSI) EP30-A, and by difference in bias analysis as described by the International Federation of Clinical Chemistry (IFCC) Working Group on Commutability. RESULTS: Using the CLSI approach, HWBs, CCMs, and PHSs were commutable with five, one, and two instruments, respectively. With the IFCC approach, HWBs were commutable with two instruments, while CCMs and PHSs were largely inconclusive or non-commutable on five instruments. CONCLUSIONS: HWBs were commutable on all instruments by the CLSI approach and may be a suitable EQA material for POC testing. Although some results differed between the IFCC and CLSI approaches, both indicated that HWBs were far superior to CCMs and PHSs in commutability.

Uncertainty evaluation in clinical chemistry, immunoassay, hematology and coagulation analytes using only external quality assessment data.

BACKGROUND: Measurement uncertainty (MU) is a parameter associated with the result of a measurement that characterizes its dispersion. We report results for estimating MU following the application of a top-down procedure using only proficiency test data to establish uncertainty levels for various analytes. METHODS: Data were obtained from 142 laboratories participating in the Beijing Center for Clinical Laboratory (BCCL) proficiency testing/external quality assessment (PT/EQA) schemes. The 24-month study included six selected PT shipments to obtain estimates for 50th percentile (median) and 90th percentile MUs and to compare those estimates to usual analytic goals. The number of laboratory participants varied for each trial. The expanded uncertainty (U) was calculated using a cover factor of k=2 for a confidence interval of 95%. All reproducibility, method and laboratory biases came from the PT/EQA data. RESULTS: The median U (k=2) ranged from 3.2% (plasma sodium, indirect ion selective electrode) to 32.8% (triglycerides, free glycerol blanking) for clinical chemistry analyte means from participants in the same method group. Immunoassay analyte median U results ranged from 11.3% (CA125 tumor marker, Roche) to 33.8% (prostate-specific antigen [PSA], Abbott). The range for median U was 3.5% (red blood cell [RBC], Abx) to 30.3% (fibrinogen [FBG], other) for hematology and coagulation analytes. The MUs for most analytes satisfied quality requirements. CONCLUSIONS: The use of PT/EQA data, when available, provides an effective means for estimating uncertainties associated with quantitative measurements. Thus, medical laboratories can calculate their own MUs. Proficiency testing organizers can provide participants with an additional MU estimate using only EQA data, which may be updated at the end of each survey.

3D cost aggregation with multiple minimum spanning trees for stereo matching.

Cost aggregation is one of the key steps in the stereo matching problem. In order to improve aggregation accuracy, we propose a cost-aggregation method that can embed minimum spanning tree (MST)-based support region filtering into PatchMatch 3D label search rather than aggregating on fixed size patches. However, directly combining PatchMatch label search and MST filtering is not straightforward, due to the extremely high complexity. Thus, we develop multiple MST structures for cost aggregation on plenty of 3D labels, and design the tree-level random search strategy to find possible 3D labels of each pixel. Extensive experiments show that our method reaches higher accuracy than the other existing cost-aggregation and global-optimization methods such as the 1D MST, the PatchMatch and the PatchMatch Filter, and currently ranks first on the Middlebury 3.0 benchmark.

Commutability of possible external quality assessment materials for cardiac troponin measurement.

BACKGROUND: The measurement of cardiac troponin is crucial in the diagnosis of myocardial infarction. The performance of troponin measurement is most conveniently monitored by external quality assessment (EQA) programs. The commutability of EQA samples is often unknown and the effectiveness of EQA programs is limited. METHODS: Commutability of possible EQA materials was evaluated. Commercial control materials used in an EQA program, human serum pools prepared from patient samples, purified analyte preparations, swine sera from model animals and a set of patient samples were measured for cTnI with 4 assays including Abbott Architect, Beckman Access, Ortho Vitros and Siemens Centaur. The measurement results were logarithm-transformed, and the transformed data for patient samples were pairwise analyzed with Deming regression and 95% prediction intervals were calculated for each pair of assays. The commutability of the materials was evaluated by comparing the logarithmic results of the materials with the limits of the intervals. Matrix-related biases were estimated for noncommutable materials. The impact of matrix-related bias on EQA was analyzed and a possible correction for the bias was proposed. RESULTS: Human serum pools were commutable for all assays; purified analyte preparations were commutable for 2 of the 6 assay pairs; commercial control materials and swine sera were all noncommutable; swine sera showed no reactivity to Vitros assay. The matrix-related biases for noncommutable materials ranged from -83% to 944%. Matrix-related biases of the EQA materials caused major abnormal between-assay variations in the EQA program and correction of the biases normalized the variations. CONCLUSION: Commutability of materials has major impact on the effectiveness of EQA programs for cTnI measurement. Human serum pools prepared from patient samples are commutable and other materials are mostly noncommutable. EQA programs should include at least one human serum pool to allow proper interpretation of EQA results.