Evaluation of serum electrolytes measurement through the 6-year trueness verification program in China

Evaluation of blood lead measurements by the 6-year external quality assessment program in China

BACKGROUND

Blood lead is an important clinical indicator. A typical tool for promoting standardisation or harmonisation is external quality assessment (EQA). Therefore, the National Centre for Clinical Laboratories (NCCL) in China launched the EQA Program for blood lead measurement in 2006 to assess its standardisation process.

METHODS

Blood lead EQA samples tested for homogeneity and stability were sent to participating laboratories. The return data were grouped according to the detection method. The robust mean value, robust coefficient of variation (CV) and standard uncertainty were calculated according to ISO 13528. The evaluation criteria were determined based on a thorough analysis of the previous pass rate and the current detection level. Overall trends in the blood lead EQA program over 6 years were investigated by calculating the pass rates of participating laboratories. We compared the pass rates and current issues of different detection methods and analysed the target values, bias and CV results of mainstream detection methods.

RESULTS

A total of 4,283 laboratories participated in EQA programs from 2017 to 2022. The pass rates were generally increasing while the inter-laboratory mean CVs were decreasing. For samples with varying concentrations, the higher the concentration, the smaller the CV. According to the evaluation criteria, the most used measurement methods, Graphite Furnace Atomic Absorption Spectrometry (GFAAS) and Tungsten Ship Atomic Absorption Spectrometry (TSAAS) demonstrated better performances than Differential Potentiometric Stripping (DPS), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Flame Atomic Absorption Spectrometry (FAAS). Furthermore, DPS, ICP-MS and FAAS outperformed Anodic Stripping Voltammetry (ASV).

CONCLUSION

Our study provides reliable information on the standardisation of blood lead measurement procedures for manufacturers and clinical laboratories. Further improvements for standardisation are still required to make laboratories more patient-centred.

Development and application of a high accuracy method for measuring Pb in blood

BACKGROUND

Lead (Pb) is an environmental pollutant, and human exposure is assessed by measuring blood Pb concentrations. Today, the use of Pb-based products is restricted, but the health effects of low Pb concentrations require investigation. For this, a high-accuracy method is needed. Here, we report a new inductively coupled plasma mass spectrometry (ICP-MS) method for quantifying Pb in blood.

METHODS

Blood samples and calibrators were gravimetrically spiked with bismuth as an internal standard, digested with ultrapure nitric acid, and diluted 100 times. The calibrators were made from high-purity reference materials supplied by the National Institute of Standards and Technology, and the sample concentration was measured using the calibration bracketing method. The analytical performance and application of the new method were investigated.

RESULTS

The method had good specificity and a negligible matrix effect. The intra- and inter-assay coefficients of variation (CVs) were <1.34 % and <1.88 %, respectively, and the total CV was <1.74 %. The range of recovery was 98.9 %-99.4 %. SRM955d, BCR-635, and BCR-636 were within the certified intervals, with mean relative bias values of 0.93 %, -0.13 %, and -0.56 %, respectively. The limit of quantification was 1.1 µg/l. The method was used to assign target values to external quality assessment samples and to assess routine methods, showing good results at high concentrations. However, at low concentrations, two laboratories did not pass.

CONCLUSIONS

This ICP-MS method is a simple, accurate method and can be a candidate reference method for blood Pb measurement. But more research will be needed to verify this.

Redesigning the surveillance of in vitro diagnostic medical devices and of medical laboratory performance by quality control in the traceability era

IVD manufacturers have total responsibility in terms of the traceability of marketed in vitro diagnostic medical devices (IVD-MD). This includes the provision of a quality control (QC) material as a part of the measuring system, suitable for traceability verification and alignment surveillance by end-users in daily practice. This material [to be used for the internal QC (IQC) component I as described in this paper] should have unbiased target values and an acceptability range corresponding to analytical performance specifications (APS) for suitable (expanded) measurement uncertainty (MU) on clinical samples. On the other hand, medical laboratories (by the IQC component II as described in this paper) should improve the IQC process and its judging criteria to establish a direct link between their performance, estimated as MU of provided results, and APS defined according to recommended models to apply corrective actions if the performance is worsening with the risk to jeopardize the clinical validity of test results. The participation to external quality assessment (EQA) programs that meet specific metrological criteria is also central to the evaluation of performance of IVD-MDs and of medical laboratories in terms of harmonization and clinical suitability of their measurements. In addition to the use of commutable materials, in this type of EQA it is necessary to assign values to them with selected reference procedures and to define and apply maximum allowable APS to substantiate the suitability of laboratory measurements in the clinical setting.

Performance of HDL-C measurements assessed by a 4-year trueness-based EQA/PT program in China

Objectives

A trueness-based EQA/PT program for high density lipoprotein cholesterol (HDL-C) was initiated. We analyzed the 4 year EQA/PT program to overview the measurement standardization for HDL-C in China.

Methods

Two levels of freshly frozen, commutable serum external quality assessment/proficiency testing (EQA/PT) materials were prepared and determined by reference measurement procedure each year. The samples were delivered to clinical laboratories and measured 15 times in 3 days. The precision [coefficient of variation (CV)], trueness (bias), and accuracy [total error (TE)] were calculated and used to evaluate measurement performance. The pass rates of individual laboratories and peer groups were analyzed using the acceptable performance from the National Cholesterol Education Program (NCEP) and biological variation as the evaluation criteria.

Results

More than 60% of laboratories use heterogeneous systems, and there was a decrease in the percentage from 2016 to 2019. About 95, 78, and 33% of laboratories met the minimum, desirable and optimum TE criteria derived from biological variation. The pass rates were 87.0% (84.7–88.8%), 58.7% (55.3–62.4%), and 97.3% (95.6–98.3%) that met the acceptable performance of TE, bias, and CV of NCEP. The homogeneous systems had higher pass rates of TE, bias, and CV than the heterogeneous groups in 2016, but they did not show apparent advantages in 2017–2019.

Conclusions

The trueness-based EQA/PT program can be used to evaluate the accuracy, reproducibility, and trueness of results. For some IVD manufacturers and individual laboratories, accuracy, especially trueness, are still problems. Efforts should be made to improve the situation and achieve better HDL-C measurement standardization.