Evaluation of serum alkaline phosphatase measurement through the 4-year trueness verification program in China

Validation of metrological traceability of the new generation of Abbott Alinity alkaline phosphatase assay

OBJECTIVES

Recently, Abbott Diagnostics marketed a new generation of Alinity enzyme assays, introducing a multiparametric calibrator [Consolidated Chemistry Calibrator (ConCC)] in place of or in addition to factor-based calibrations. For alkaline phosphatase (ALP), both calibration options are offered, i.e., with ConCC (ALP2) and with an experimental calibration factor (ALP2F). Both options are declared traceable to the 2011 IFCC reference measurement procedure (RMP). Before to replace the old generation (ALP1) with the new one, we decided to validate the trueness of ALP2/ALP2F.

METHODS

Three approaches were employed: (a) preliminary comparison on 48 native frozen serum samples with ALP1, of which traceability to RMP was previously successfully verified; (b) examination of three banked serum pools (BSP) with values assigned by RMP; (c) direct comparison with RMP on a set of 24 fresh serum samples. Bias estimation and regression studies were performed, and the standard measurement uncertainty associated with ALP measurements on clinical samples (uresult) was estimated and compared with established analytical performance specifications (APS). ConCC commutability was also assessed.

RESULTS

A positive proportional bias was found with both ALP2 and ALP2F when compared to ALP1 and RMP. This positive bias was confirmed on BSP: in average, +13.1 % for ALP2 and +10.0 % for ALP2F, respectively. uresult were 13.28 % for ALP2 and 10.04 % for ALP2F, both not fulfilling the minimum APS of 4.0 %. Furthermore, ConCC was not commutable with clinical samples.

CONCLUSIONS

Our results unearth problems in the correct implementation of traceability of Alinity ALP2/ALP2F, with the risk for the new assay to be unfit for clinical purposes.

Development of a glucose reference material in human serum for clinical assay standardization

BACKGROUND

Blood glucose is an important monosaccharide functioning as the main source of energy for the human body. The accurate measurement of blood glucose is crucial for the screening, diagnosis, and monitoring of diabetes and diabetes-associated diseases. To assure the reliability and traceability of blood glucose measurements, we developed a reference material (RM) for use in human serum at two different concentrations, which were certified by the National Institute of Metrology (NIM) as GBW(E)091040 and GBW(E)091043.

METHODS

Raw serum samples were collected from residual samples after clinical testing, filtered, and repackaged under mild stirring. The homogeneity and stability of the samples were examined according to ISO Guide 35: 2017. Commutability was evaluated in compliance with CLSI EP30-A. Value assignment was carried out in six certified reference laboratories using the JCTLM-listed reference method for serum glucose. Moreover, the RMs was further applied in a trueness verification program.

RESULTS

The developed RMs was homogeneous and commutable enough for clinical use. They were also stable for 24 h at 2-8 ℃ or 20-25 ℃ and for at least 4 years at - 70 ℃. The certified values were 5.20 ± 0.18 mmol/L and 8.18 ± 0.19 mmol/L (k = 2) for GBW(E)091040 and GBW(E)091043, respectively. The pass rates were evaluated by bias, coefficient of variation (CV), and total error (TE) for 66 clinical laboratories in the trueness verification program were 57.6%, 98.5%, and 89.4% of GBW(E)091040, and 51.5%, 98.5%, and 90.9% of GBW(E)091043, respectively.

CONCLUSION

The developed RM could be used for the standardization of reference and clinical systems with satisfactory performance and traceable values, providing strong support for the accurate measurement of blood glucose.

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.

Association of Serum Alkaline Phosphatase with the TG/HDL Ratio and TyG Index in Korean Adults

Alkaline phosphatase (ALP) has long been considered a marker of hepatobiliary and bone disorders, but recent studies have shown that increased ALP activity is correlated with various cardio-metabolic diseases. Thus, we investigated the association of serum ALP level with surrogate markers of insulin resistance such as triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C ratio) and triglyceride and glucose (TyG) index in the general population. The study included 12,868 men and women aged 19 years and older. Participants were categorized into four groups based on serum ALP level (U/L) as follows: Q1: 55-190 U/L, Q2: 191-224 U/L, Q3: 225-265 U/L, and Q4: 266-923 U/L for men, Q1: 48-161 U/L, Q2: 162-198 U/L, Q3: 199-245 U/L, Q4: 246-790 U/L for women. The insulin resistance cut-off levels were defined corresponding to the 75th percentile of the TyG index and TG/HDL-C ratio in the current samples. Odds ratios (ORs) with 95% confidence intervals (CIs) of insulin resistance according to quartile of serum ALP level were calculated using weighted multivariate logistic regression analysis. Compared with Q1, the adjusted OR (95% CI) for insulin resistance of the Q4 serum ALP group was 1.517 (1.234-1.866) in men and 1.881 (1.399-2.528) in women using the TG/HDL-C ratio and 1.374 (1.093-1.728) in men and 2.047 (1.468-2.855) in women using the TyG index after adjusting for confounding variables. Serum ALP levels are independently and positively associated with surrogate markers of insulin resistance in Korean adults.

Development of a designated comparison method for alkaline phosphatase measurements and its application to evaluating routine methods

The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) published the reference measurement procedure (RMP) for ALP measurement in 2011. However, the RMP is of high requirements for laboratories, complicated, time-consuming and high cost of reagents. Many manufacturers do not trace results to the higher procedure. And there is currently no designated comparison method (DCM) for ALP measurement. Thus, the standardization of ALP measurement is hindered. Automatic biochemical analyzers are easy to operate and widely used in clinical laboratories. Therefore, according to the RMP, establishing a DCM based on an automatic biochemical analyzer will be a practical way to establish traceability to the accuracy base and promote the standardization of ALP measurement. On the basis of conforming to the RMP recommended by IFCC as far as possible, the DCM was established based on a Thermo Indiko automatic biochemical analyzer. Performances of the method were validated. The DCM repeatability and within laboratory imprecision was <1% and <2.5%, respectively. For evaluation of trueness, the biases were within the equivalent limits. Measurement procedure comparisons and biases estimation were carried out between the DCM, the RMP, and the six routine methods using a panel of 40 individual human serum samples. The comparisons between the DCM and the RMP gave satisfying results. Compared with the DCM, the relative biases of some routine methods failed to meet the bias limit derived from biological variation.