Validation of Becton Dickinson Barricor™ tubes for use with Abbott Alinity™ and Siemens Atellica® highly sensitive cardiac troponin I measuring systems.

BACKGROUND: BD Barricor™ tubes have been proposed to decrease laboratory turnaround time (TAT). We analytically validated and then clinically verified these tubes for use with Abbott Alinity™ and Siemens Atellica® highly sensitive cardiac troponin I (hs-cTnI) assays. METHODS: hs-cTnI measurements were undertaken in paired Barricor™ and in-use PSTII™ tubes on both systems. 359 matched samples with hs-cTnI levels between 3 and 15,000 ng/L (Atellica® values) were used to assess the hemolysis rate and make method comparisons. 599 paired patient samples were collected on emergency department (ED) admission to compare the performance of the rapid acute myocardial infarction (AMI) rule-out strategy based on hs-cTnI concentrations lower than recommended thresholds (<4 ng/L Alinity™; <5 ng/L Atellica®) when different tubes and systems were employed. RESULTS: No between-tube differences in hemolysis rate were seen when free hemoglobin concentrations in plasma samples were ≥0.25 g/L, even if PSTII™ showed a significant increase of hemolysis rate vs. Barricor™ (31% vs. 22%, p=0.007) when a lower cut-off for hemolysis (≥0.11 g/L) was employed on the Atellica® detection system. The alternate use of these tubes did not influence the hs-cTnI results obtained from either of the two assays, which remained markedly biased (~40%) irrespective of the tube used. The expected optimal ability of very low hs-cTnI values on ED admission for ruling out AMI was confirmed by using both systems regardless of the tube type. CONCLUSIONS: Barricor™ and PSTII™ tubes can provide analytically equivalent hs-cTnI results when used on either Alinity™ or Atellica® hs-cTnI assays.

An improved implementation of metrological traceability concepts is needed to benefit from standardization of laboratory results.

Non-harmonization of laboratory results represents a concrete risk for patient safety. To avoid harms, it is agreed that measurements by in vitro diagnostic medical devices (IVD-MD) on clinical samples should be traceable to higher-order references and adjusted to give the same result. However, metrological traceability is not a formal claim and has to be correctly implemented, which in practice does not happen for a non-negligible number of measurands. Stakeholders, such as higher-order reference providers, IVD manufacturers, and External Quality Assessment organizers, have major responsibilities and should improve their contribution by unambiguously and rigorously applying what is described in the International Organization for Standardization 17511:2020 standard and other documents provided by the international scientific bodies, such as Joint Committee on Traceability in Laboratory Medicine and IFCC. For their part, laboratory professionals should take responsibility to abandon non-selective methods and move to IVD-MDs displaying proper selectivity, which is one of the indispensable prerequisites for the correct implementation of metrological traceability. The practicality of metrological traceability concepts is not impossible but relevant education and appropriate training of all involved stakeholders are essential to obtain the expected benefits in terms of standardization.

Laboratory investigation of peritoneal fluids: an updated practical approach based on the available evidence.

Even though analysis of peritoneal fluids (PF) is often requested to medical laboratories for biochemical and morphological tests, there is still no mutual agreement on what the most appropriate way is to manage PF samples and which tests should be appropriately executed. In this update, we tried to identify the most useful tests for PF analysis to establish best practice indications. We performed a literature review and examined available guidelines to select the most appropriate tests by an evidence-based approach. Accordingly, the basic PF profile should include (1) serum to effusion albumin gradient and (2) automated cell counts with differential analysis. This profile allows to determine the PF nature, differentiating between 'high-albumin gradient' and 'low-albumin gradient' effusions, which helps to identify the pathophysiological process causing the ascites formation. Restricted to specific clinical situations, additional tests can be requested as follows: PF lactate dehydrogenase (LDH) and glucose, to exclude (LDH) or confirm (glucose) secondary bacterial peritonitis; PF total protein, to differentiate ascites of cardiac origin from other causes; PF (pancreatic) amylase, for the identification of pancreatic ascites; PF bilirubin, when a choleperitoneum is suspected; PF triglycerides, in differentiating chylous from pseudochylous ascites and PF creatinine, to detect intraperitoneal urinary leakage.

State-of-the-art model for derivation of analytical performance specifications: how to define the highest level of analytical performance technically achievable.

To be accurate and equivalent among assays, laboratory results should be traceable to higher-order references and their quality should fulfill maximum allowable measurement uncertainty (MU) as defined to fit the intended clinical use. Accordingly, laboratory professionals should estimate and validate MU of performed tests using appropriate analytical performance specifications (APS). Current consensus supports the derivation of APS by using one of the three models established by the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Strategic Conference held in Milan in 2014. It is recognized that some models are better suited for certain measurands than for others and the attention should be primarily directed towards their biological and clinical characteristics. Among others, model 3 should reflect the state of the art of the measurements that can be defined as the best analytical performance that is technically achievable. Taking serum C-reactive protein and ferritin as examples, here we describe the theoretical premises and the experimental protocol to be used to derive APS for MU when a measurand is allocated to this model. Although the model lacks a direct relationship with clinical outcomes, useful information about the in vitro diagnostic medical device performance and the average quality of provided results may be obtained.

Analytical performance specifications for combined uncertainty budget in the implementation of metrological traceability.

In addition to the correct implementation of calibration traceability, the definition and fulfillment of maximum allowable measurement uncertainty (MAU) are essential in assuring that laboratory measurements are clinically usable. Across the entire calibration hierarchy, three major contributors to the measurement uncertainty (MU) budget are identified, starting with the higher-order reference providers, extending through the in vitro diagnostic (IVD) manufacturers and their processes for assigning calibrator values, and ending with medical laboratories generating the random variability of results reported to clinicians. To understand if it is possible to achieve MAU and, consequently, to fix the possible drawbacks, the definition of combined MU budget limits across the entire calibration hierarchy has a central role. In particular, quality specifications for MU of reference and commercial calibrator materials should be defined according to the MAU on clinical samples. All involved stakeholders (i.e., higher-order reference providers, IVD manufacturers, medical laboratories) should be prepared to improve their performance whenever the clinical application of the test is made questionable by the failure to achieve MAU.

What the Milan conference has taught us about analytical performance specification model definition and measurand allocation.

Analytical performance specifications (APS) represent the criteria that specify the quality required for laboratory test information to satisfy clinical needs. In 2014 the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) considered timely to update the topic of APS by organizing a conference in Milan in which some strategic concepts were proposed. Here I summarize the essential points representing the EFLM Strategic Conference heritage and discuss the approaches that will permit us to become more concrete, including roles and main actions expected from each of involved stakeholders for contributing a quantum leap forward in the way of practicality of Milan consensus about APS.

Performance Evaluation of a Novel Non-Invasive Test for the Detection of Advanced Liver Fibrosis in Metabolic Dysfunction-Associated Fatty Liver Disease.

Metabolic dysfunction-associated fatty liver disease (MAFLD) may progress to advanced liver fibrosis (ALF). We evaluated the diagnostic accuracy of a novel Liver Fibrosis Risk Index (LFRI) in MAFLD subjects using transient elastography (TE) as the reference method for liver fibrosis measurement and then the diagnostic performance of a new two-step non-invasive algorithm for the detection of ALF risk in MAFLD, using Fibrosis-4 (FIB-4) followed by LFRI and comparing it to the reference algorithm based on FIB-4 and TE. We conducted a prospective study on 104 MAFLD European adult subjects. All consenting subjects underwent TE and measurements of FIB-4 and LFRI. For FIB-4 and TE, validated cut-offs were used. An ROC analysis showed that LFRI diagnosed severe fibrosis with moderate accuracy in MAFLD subjects with a negative predictive value above 90%. Using the new algorithm with LFRI thresholds recommended by the manufacturer, the number of subjects classified into ALF risk groups (low, intermediate, or high) differed significantly when compared with the reference algorithm (p = 0.001), with moderate agreement between them (weighted kappa (95% CI) = 0.59 (0.41-0.77)). To improve the performance of the LFRI-based algorithm, we modified cut-off points based on ROC curves obtained by dividing the study population according to the reference algorithm and observed no difference between algorithms (p = 0.054) in categorizing ALF risk, with a slight increase in the total agreement (weighted kappa (95% CI) = 0.63 (0.44-0.82)). Our findings suggest that using the novel LFRI as a second-line test may represent a potential alternative for liver fibrosis risk stratification in MAFLD patients; however, modified cut-offs are needed to optimize its performance.

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.

Documenting and validating metrological traceability of serum alanine aminotransferase measurements: a priority for medical laboratory community for providing high quality service in hepatology.

Alanine aminotransferase (ALT) represents the first-level test to detect individuals with hepatocellular damage of any etiology. However, it has been highlighted that the lack of assay harmonization may lead to overdiagnosis and unnecessary further testing if guideline-recommended fixed cut-offs are uncritically employed. To solve the issue of ALT (dis)harmonization and improve the interpretation of its values, a series of urgent actions for documenting and validating metrological traceability of serum ALT measurements, as described in this paper, are no longer postponeable. It is time that all medical laboratory stakeholders (in vitro diagnostic manufacturers, laboratorians, external quality assessment scheme organizers) actively co-operate to implement the ALT standardization in a concerted action following well-established theoretical assumptions and applying experimental approaches described in literature.

APS calculator: a data-driven tool for setting outcome-based analytical performance specifications for measurement uncertainty using specific clinical requirements and population data.

OBJECTIVES: According to ISO 15189:2022, analytical performance specifications (APS) should relate to intended clinical use and impact on patient care. Therefore, we aimed to develop a web application for laboratory professionals to calculate APS based on a simulation of the impact of measurement uncertainty (MU) on the outcome using the chosen decision limits, agreement thresholds, and data of the population of interest. METHODS: We developed the "APS Calculator" allowing users to upload and select data of concern, specify decision limits and agreement thresholds, and conduct simulations to determine APS for MU. The simulation involved categorizing original measurand concentrations, generating measured (simulated) results by introducing different degrees of MU, and recategorizing measured concentrations based on clinical decision limits and acceptable clinical misclassification rates. The agreements between original and simulated result categories were assessed, and values that met or exceeded user-specified agreement thresholds that set goals for the between-category agreement were considered acceptable. The application generates contour plots of agreement rates and corresponding MU values. We tested the application using National Health and Nutrition Examination Survey data, with decision limits from relevant guidelines. RESULTS: We determined APS for MU of six measurands (blood total hemoglobin, plasma fasting glucose, serum total and high-density lipoprotein cholesterol, triglycerides, and total folate) to demonstrate the potential of the application to generate APS. CONCLUSIONS: The developed data-driven web application offers a flexible tool for laboratory professionals to calculate APS for MU using their chosen decision limits and agreement thresholds, and the data of the population of interest.

Recommendations for Setting a Criterion and Assessing Commutability of Sample Materials Used in External Quality Assessment/Proficiency Testing Schemes.

It is important for external quality assessment materials (EQAMs) to be commutable with clinical samples; i.e., they should behave like clinical samples when measured using end-user clinical laboratory in vitro diagnostic medical devices (IVD-MDs). Using commutable EQAMs makes it possible to evaluate metrological traceability and/or equivalence of results between IVD-MDs. The criterion for assessing commutability of an EQAM between 2 IVD-MDs is that its result should be within the prediction interval limits based on the statistical distribution of the clinical sample results from the 2 IVD-MDs being compared. The width of the prediction interval is, among other things, dependent on the analytical performance characteristics of the IVD-MDs. A presupposition for using this criterion is that the differences in nonselectivity between the 2 IVD-MDs being compared are acceptable. An acceptable difference in nonselectivity should be small relative to the analytical performance specifications used in the external quality assessment scheme. The acceptable difference in nonselectivity is used to modify the prediction interval criterion for commutability assessment. The present report provides recommendations on how to establish a criterion for acceptable commutability for EQAMS, establish the difference in nonselectivity that can be accepted between IVD-MDs, and perform a commutability assessment. The report also contains examples for performing a commutability assessment of EQAMs.

Recommendations for Setting a Criterion for Assessing Commutability of Secondary Calibrator Certified Reference Materials.

A secondary higher-order calibrator is required to be commutable with clinical samples to be suitable for use in the calibration hierarchy of an end-user clinical laboratory in vitro diagnostic medical device (IVD-MD). Commutability is a property of a reference material that means results for a reference material and for clinical samples have the same numeric relationship, within specified limits, across the measurement procedures for which the reference material is intended to be used. Procedures for assessing commutability have been described in the literature. This report provides recommendations for establishing a quantitative criterion to assess the commutability of a certified reference material (CRM). The criterion is the maximum allowable noncommutability bias (MANCB) that allows a CRM to be used as a calibrator in a calibration hierarchy for an IVD-MD without exceeding the maximum allowable combined standard uncertainty for a clinical sample result (umaxCS). Consequently, the MANCB is derived as a fraction of the umaxCS for the measurand. The suitability of an MANCB for practical use in a commutability assessment is determined by estimating the number of measurements of clinical samples and CRMs required based on the precision performance and nonselectivity for the measurand of the measurement procedures in the assessment. Guidance is also provided for evaluating indeterminate commutability conclusions and how to report results of a commutability assessment.

Corrigendum: Definition of the immune parameters related to COVID-19 severity.

[This corrects the article DOI: 10.3389/fimmu.2022.850846.].