Understanding the limitations of your assay using EQA data with serum creatinine as an example.

OBJECTIVES: Laboratories need to take into consideration the specificity and imprecision of assays not only in verification, but also of quality assessment. This study investigates the composition of serum used in EQA materials by comparing material from a single and multiple donors (pooled material), across multiple methods, using creatinine as an example. METHODS: Sixteen different serum matrices were distributed as 36 specimens through the UK NEQAS for Acute and Chronic Kidney Disease Scheme from March 2022 to March 2023. Male-only and female-only serum was used as single donations, pooled donations, unmanipulated or with added exogenous creatinine. Specimens were distributed to primarily UK participants (approximately n=500) for creatinine analysis. Data has been reviewed by method compared to the enzymatic creatinine method principle mean. RESULTS: From the 16 different matrices, only the enzymatic creatinine assay systems from Roche Cobas and Siemens Atellica met the minimum acceptable bias goal, from biological data, of 5.6 %, in all specimens. Pooled material showed less variation in bias across all methods. CONCLUSIONS: Since Laboratories invest a lot of time and money in quality management, they need to know the limitations of their assays so that they are not investigating 'apparent' EQA/IQC problems which are purely due to non-specific, imprecise assay, rather than an analytical issue in their laboratory. When large numbers of individual donations are combined, interferents are essentially diluted out. Therefore, if EQA material is of this type it will be very difficult to determine the actual assay's bias and variability.

Report from the HarmoSter study: different LC-MS/MS androstenedione, DHEAS and testosterone methods compare well; however, unifying calibration is a double-edged sword.

OBJECTIVES: Current liquid chromatography-tandem mass spectrometry (LC-MS/MS) applications for circulating androgen measurements are technically diverse. Previously, variable results have been reported for testosterone. Data are scarce for androstenedione and absent for dehydroepiandrosterone sulfate (DHEAS). We assessed the agreement of androstenedione, DHEAS and testosterone LC-MS/MS measurements among nine European centers and explored benefits of calibration system unification. METHODS: Androgens were measured twice by laboratory-specific procedures in 78 patient samples and in EQA materials. Results were obtained by in-house and external calibration. Intra- and inter-laboratory performances were valued. RESULTS: Intra-laboratory CVs ranged between 4.2-13.2 % for androstenedione, 1.6-10.8 % for DHEAS, and 4.3-8.7 % and 2.6-7.1 % for female and male testosterone, respectively. Bias and trueness in EQA materials were within ±20 %. Median inter-laboratory CV with in-house vs. external calibration were 12.0 vs. 9.6 % for androstenedione (p<0.001), 7.2 vs. 4.9 % for DHEAS (p<0.001), 6.4 vs. 7.6 % for female testosterone (p<0.001) and 6.8 and 7.4 % for male testosterone (p=0.111). Median bias vs. all laboratory median with in-house and external calibration were -13.3 to 20.5 % and -4.9 to 18.7 % for androstenedione, -10.9 to 4.8 % and -3.4 to 3.5 % for DHEAS, -2.7 to 6.5 % and -11.3 to 6.6 % for testosterone in females, and -7.0 to 8.5 % and -7.5 to 11.8 % for testosterone in males, respectively. CONCLUSIONS: Methods showed high intra-laboratory precision but variable bias and trueness. Inter-laboratory agreement was remarkably good. Calibration system unification improved agreement in androstenedione and DHEAS, but not in testosterone measurements. Multiple components, such as commutability of calibrators and EQA materials and internal standard choices, likely contribute to inter-laboratory variability.

Artificially raised creatinine concentrations due to analytical interference for samples contaminated with total parenteral nutrition fluid.

BACKGROUND: A sample received in the laboratory from a patient receiving total parenteral nutrition (TPN) indicated that the patient may have renal dysfunction, but the results were not considered to be reliable enough to report. Investigations using a reference method for measurement of creatinine confirmed positive interference in the creatinine assay and distribution of samples via an External Quality Assessment (EQA) Scheme showed that this positive interference was method dependent. METHODS: Residual TPN fluid (Nutriflex Lipid Special) left in the bag after the patient had completed the infusion was collected and added to a patient serum pool in increasing amounts and distributed to different laboratories for analysis of creatinine and glucose through an EQA Scheme. RESULTS: Positive interference in a number of different creatinine assays was identified as a result of a component in the TPN fluid. Positive interference from high concentrations of glucose has been demonstrated to be a cause for falsely high results in Jaffe creatinine assays. CONCLUSIONS: The concern would be that a sample contaminated with TPN fluid would have both abnormal electrolytes and creatinine concentrations and give the impression that the patient was in renal failure due to analytical interference in the creatinine assay and laboratory staff need to be aware of this problem.

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.

Standardising the biochemical confirmation of adult male hypogonadism; a joint position statement by the Society for Endocrinology and Association of Clinical Biochemistry and Laboratory Medicine.

Background: Inter-assay variation between different immunoassays and different mass spectrometry methods hampers the biochemical confirmation of male hypogonadism. Furthermore, some laboratories utilis eassay manufacturer reference ranges that do not necessarily mirror assay performance characteristics, with the lower limit of normality ranging from 4.9 nmol/L to 11 nmol/L. The quality of the normative data underlying commercial immunoassay reference ranges is uncertain.Design: A working group reviewed published evidence and agreed upon standardised reporting guidance to augment total testosterone reports. Results: Evidence-based guidance on appropriate blood sampling, clinical action limits, and other major factors likely to affect the interpretation of results are provided. Conclusions: This article aims to improve the quality of the interpretation of testosterone results by non-specialist clinicians. It also discusses approaches for assay harmonisation which have been successful in some but not all healthcare systems.

Standardising the biochemical confirmation of adult male hypogonadism: A joint position statement by the Society for Endocrinology and Association of Clinical Biochemistry and Laboratory Medicine.

BACKGROUND: Inter-assay variation between different immunoassays and different mass spectrometry methods hampers the biochemical confirmation of male hypogonadism. Furthermore, some laboratories utilise assay manufacturer reference ranges that do not necessarily mirror assay performance characteristics, with the lower limit of normality ranging from 4.9 nmol/L to 11 nmol/L. The quality of the normative data underlying commercial immunoassay reference ranges is uncertain. DESIGN: A working group reviewed published evidence and agreed upon standardised reporting guidance to augment total testosterone reports. RESULTS: Evidence-based guidance on appropriate blood sampling, clinical action limits, and other major factors likely to affect the interpretation of results are provided. CONCLUSIONS: This article aims to improve the quality of the interpretation of testosterone results by non-specialist clinicians. It also discusses approaches for assay harmonisation which have been successful in some but not all healthcare systems.

Variation of eGFR reporting and CKD equations used in the United Kingdom.

BACKGROUND: UK Clinical laboratories have been routinely reporting an estimated glomerular filtration rate (eGFR) based on creatinine measurements using an eGFR equation since the early 2000s. Though there have been recommendations to use enzymatic based creatinine assays, and a recommendation of which equation to use, there still remains a high degree of variation in calculated eGFR results. METHODS: Data from the UK NEQAS for Acute and Chronic Kidney Disease Scheme have been reviewed to look at the CKD equations that are currently in use in the UK and the impact on eGFR results reported. The UK NEQAS for Acute and Chronic Kidney Disease has over 400 participants measuring creatinine across all major clinical biochemistry platforms. RESULTS: An audit of EQA registration against results returned showed that in February 2022 at most 44% of registered participants were correctly reporting the 2009 CKD-EPI equation. At higher creatinine concentrations (which give rise to lower eGFR results), the spread of eGFRs is tight and there is little difference between results from different method principles. However, at lower creatinine concentrations, where it is known that there is more variation in creatinine depending on method choice, both method principle and eGFR equation choice can influence calculated eGFR. In some cases, this can impact CKD Stage classification. CONCLUSIONS: CKD is a serious public health issue that requires accurate assessment of eGFR. Laboratories should be in constant dialogue with their renal teams about their creatinine assay performance and impact on eGFR reporting across their service.

National recommendations to standardise acute kidney injury detection and alerting.

BACKGROUND: National Health Service England issued a Patient Safety Alert in 2014 mandating all acute Trusts in England to implement Acute Kidney Injury (AKI) warning stage results and to do so using a standardised algorithm. In 2021, the Renal and Pathology Getting It Right First Time (GIRFT) teams found significant variation in AKI reporting across the UK. A survey was designed to capture information on the entire AKI detection and alerting process to investigate the potential sources of this unwarranted variation. METHODS: In August 2021, an online survey consisting of 54 questions was made available to all UK laboratories. The questions covered creatinine assays, laboratory information management systems (LIMS), the AKI algorithm and AKI reporting. RESULTS: We received 101 responses from laboratories. Data were reviewed for England only - 91 laboratories. Findings included that 72% used enzymatic creatinine. In addition, 7 manufacturer-analytical platforms, 15 different LIMS and a wide range of creatinine reference ranges were in use. In 68% of laboratories, the AKI algorithm was installed by the LIMS provider. Marked variation was found in the minimum age of AKI reporting with only 18% starting at the recommended 1 month/28-days. Some 89% phoned all new AKI2s and AKI3s, as per AKI guidance while 76% provided comments/hyperlinks in reports. CONCLUSIONS: The national survey has identified laboratory practices that potentially contribute to unwarranted variation in the reporting of AKI in the England. This has formed the basis for improvement work to remedy the situation, including national recommendations, included within this article.

Report from the HarmoSter study: impact of calibration on comparability of LC-MS/MS measurement of circulating cortisol, 17OH-progesterone and aldosterone.

OBJECTIVES: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is recommended for measuring circulating steroids. However, assays display technical heterogeneity. So far, reproducibility of corticosteroid LC-MS/MS measurements has received scant attention. The aim of the study was to compare LC-MS/MS measurements of cortisol, 17OH-progesterone and aldosterone from nine European centers and assess performance according to external quality assessment (EQA) materials and calibration. METHODS: Seventy-eight patient samples, EQA materials and two commercial calibration sets were measured twice by laboratory-specific procedures. Results were obtained by in-house (CAL1) and external calibrations (CAL2 and CAL3). We evaluated intra and inter-laboratory imprecision, correlation and agreement in patient samples, and trueness, bias and commutability in EQA materials. RESULTS: Using CAL1, intra-laboratory CVs ranged between 2.8-7.4%, 4.4-18.0% and 5.2-22.2%, for cortisol, 17OH-progesterone and aldosterone, respectively. Trueness and bias in EQA materials were mostly acceptable, however, inappropriate commutability and target value assignment were highlighted in some cases. CAL2 showed suboptimal accuracy. Median inter-laboratory CVs for cortisol, 17OH-progesterone and aldosterone were 4.9, 11.8 and 13.8% with CAL1 and 3.6, 10.3 and 8.6% with CAL3 (all p<0.001), respectively. Using CAL1, median bias vs. all laboratory-medians ranged from -6.6 to 6.9%, -17.2 to 7.8% and -12.0 to 16.8% for cortisol, 17OH-progesterone and aldosterone, respectively. Regression lines significantly deviated from the best fit for most laboratories. Using CAL3 improved cortisol and 17OH-progesterone between-method bias and correlation. CONCLUSIONS: Intra-laboratory imprecision and performance with EQA materials were variable. Inter-laboratory performance was mostly within specifications. Although residual variability persists, adopting common traceable calibrators and RMP-determined EQA materials is beneficial for standardization of LC-MS/MS steroid measurements.

Society for Endocrinology guidelines for testosterone replacement therapy in male hypogonadism.

Male hypogonadism (MH) is a common endocrine disorder. However, uncertainties and variations in its diagnosis and management exist. There are several current guidelines on testosterone replacement therapy that have been driven predominantly by single disciplines. The Society for Endocrinology commissioned this new guideline to provide all care providers with a multidisciplinary approach to treating patients with MH. This guideline has been compiled using expertise from endocrine (medical and nursing), primary care, clinical biochemistry, urology and reproductive medicine practices. These guidelines also provide a patient perspective to help clinicians best manage MH.

Feasibility for aggregation of commutable external quality assessment results to evaluate metrological traceability and agreement among results.

Objectives: External quality assessment (EQA) with commutable samples is used for assessing agreement of results for patients' samples. We investigated the feasibility to aggregate results from four different EQA schemes to determine the bias between different measurement procedures and a reference target value. Methods: We aggregated EQA results for creatinine from programs that used commutable EQA material by calculating the relative difference between individual participant results and the reference target value for each sample. The means and standard errors of the means were calculated for the relative differences. Results were partitioned by methods, manufacturers and instrument platforms to evaluate the biases for the measurement procedures. Results: Data aggregated for enzymatic methods had biases that varied from -8.2 to 3.8% among seven instrument platforms for creatinine at normal concentrations (61-85 µmol/L). EQA schemes differed in the evidence provided about the commutability of their samples, and in the amount of detail collected from participants regarding the measurement procedures which limited the ability to sub-divide aggregated data by instrument platforms and models. Conclusions: EQA data could be aggregated from four different programs using different commutable samples to determine bias among different measurement procedures. Criteria for commutability for EQA samples as well as standardization of reporting the measurement methods, reagents, instrument platforms and models used by participants are needed to improve the ability to aggregate the results for optimal assessment of performance of measurement procedures. Aggregating data from a larger number of EQA schemes is feasible to assess trueness on a global scale.

IFCC Working Group Recommendations for Correction of Bias Caused by Noncommutability of a Certified Reference Material Used in the Calibration Hierarchy of an End-User Measurement Procedure.

Establishing metrological traceability to an assigned value of a matrix-based certified reference material (CRM) that has been validated to be commutable among available end-user measurement procedures (MPs) is central to producing equivalent results for the measurand in clinical samples (CSs) irrespective of the clinical laboratory MPs used. When a CRM is not commutable with CSs, the bias due to noncommutability will be propagated to the CS results causing incorrect metrological traceability to the CRM and nonequivalent CS results among different MPs. In a commutability assessment, a conclusion that a CRM is commutable or noncommutable for use with a specific MP is made when the difference in bias between the CRM and CSs meets or does not meet a criterion for that specific MP when compared to other MPs. A conclusion regarding commutability or noncommutability requires that the magnitude of the difference in bias observed in the commutability assessment remains unchanged over time. This conclusion requires the CRM to be stable and no substantive changes in the MPs. These conditions should be periodically reverified. If an available CRM is determined to be noncommutable for a specific MP, that CRM can be used in the calibration hierarchy for that MP when an appropriately validated MP-specific correction for the noncommutability bias is included. We describe with examples how a MP-specific correction and its uncertainty can be developed and applied in a calibration hierarchy to achieve metrological traceability of results for CSs to the CRM's assigned value.

Predicting renal disease progression in a large contemporary cohort with type 1 diabetes mellitus.

AIMS/HYPOTHESIS: The aim of this study was to provide data from a contemporary population-representative cohort on rates and predictors of renal decline in type 1 diabetes. METHODS: We used data from a cohort of 5777 people with type 1 diabetes aged 16 and older, diagnosed before the age of 50, and representative of the adult population with type 1 diabetes in Scotland (Scottish Diabetes Research Network Type 1 Bioresource; SDRNT1BIO). We measured serum creatinine and urinary albumin/creatinine ratio (ACR) at recruitment and linked the data to the national electronic healthcare records. RESULTS: Median age was 44.1 years and diabetes duration 20.9 years. The prevalence of CKD stages G1, G2, G3 and G4 and end-stage renal disease (ESRD) was 64.0%, 29.3%, 5.4%, 0.6%, 0.7%, respectively. Micro/macroalbuminuria prevalence was 8.6% and 3.0%, respectively. The incidence rate of ESRD was 2.5 (95% CI 1.9, 3.2) per 1000 person-years. The majority (59%) of those with chronic kidney disease stages G3-G5 did not have albuminuria on the day of recruitment or previously. Over 11.6 years of observation, the median annual decline in eGFR was modest at -1.3 ml min-1 [1.73 m]-2 year-1 (interquartile range [IQR]: -2.2, -0.4). However, 14% experienced a more significant loss of at least 3 ml min-1 [1.73 m]-2. These decliners had more cardiovascular disease (OR 1.9, p = 5 × 10-5) and retinopathy (OR 1.3 p = 0.02). Adding HbA1c, prior cardiovascular disease, recent mean eGFR and prior trajectory of eGFR to a model with age, sex, diabetes duration, current eGFR and ACR maximised the prediction of final eGFR (r2 increment from 0.698 to 0.745, p < 10-16). Attempting to model nonlinearity in eGFR decline or to detect latent classes of decliners did not improve prediction. CONCLUSIONS: These data show much lower levels of kidney disease than historical estimates. However, early identification of those destined to experience significant decline in eGFR remains challenging.

Effect of blood volume on analytical bias in dried blood spots prepared for newborn screening external quality assurance.

Aim: Dried blood spots (DBS) are used for the analysis of more than 2000 biomarkers. We assessed a range of analyte concentrations and diameters of DBS. Materials & methods: DBS samples were created by the application of increasing volumes of whole blood prepared by the UK NEQAS Quality Assurance Laboratory. Samples were analyzed in four separate laboratories. Results: Volumes less than 25 µl (8 mm) and more than 75 µl (14 mm) created unsatisfactory analytical biases. Results obtained from peripheral subpunches tended to be higher than those from a central subpunch. Conclusion: DBS diameters formed from nonvolumetric application of blood to filter paper can be used to assess whether measurement bias will be within acceptable limits according to the analyte being quantified. DBS received for newborn screening in the UK with diameters less than 8 mm and those more than 14 mm should be rejected.

IFCC Working Group Recommendations for Assessing Commutability Part 1: General Experimental Design.

Commutability is a property of a reference material (RM) that relates to the closeness of agreement between results for an RM and results for clinical samples (CSs) when measured by ≥2 measurement procedures (MPs). Commutability of RMs used in a calibration traceability scheme is an essential property for them to be fit for purpose. Similarly, commutability of trueness controls or external quality assessment samples is essential when those materials are used to assess trueness of results for CSs. This report is part 1 of a 3-part series describing how to assess commutability of RMs. Part 1 defines commutability and addresses critical components of the experimental design for commutability assessment, including selection of individual CSs, use of pooled CSs, qualification of MPs for inclusion, establishing criteria for the determination that an RM is commutable, generalization of commutability conclusions to future measurements made with the MPs included in the assessment, and information regarding commutability to be included in the certificate for an RM. Parts 2 and 3 in the series present 2 different statistical approaches to commutability assessment that use fixed criteria related to the medical decisions that will be made using the laboratory test results.

IFCC Working Group Recommendations for Assessing Commutability Part 3: Using the Calibration Effectiveness of a Reference Material.

A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator based on its ability to fulfill its intended use in a calibration traceability scheme to produce equivalent clinical sample (CS) results among different measurement procedures (MPs) for the same measurand. Three sources of systematic error are elucidated in the context of creating the calibration model for translating MP signals to measurand amounts: calibration fit, calibrator level trueness, and commutability. An example set of 40 CS results from 7 MPs is used to illustrate estimation of bias and variability for each MP. The candidate RM is then used to recalibrate each MP, and its effectiveness in reducing the systematic error among the MPs within an acceptable level of equivalence based on medical requirements confirms its commutability for those MPs. The RM is declared noncommutable for MPs for which, after recalibration, the CS results do not agree with those from other MPs. When a lack of agreement is found, other potential causes, including lack of calibration fit, should be investigated before concluding the RM is noncommutable. The RM is considered fit for purpose for those MPs where commutability is demonstrated.

IFCC Working Group Recommendations for Assessing Commutability Part 2: Using the Difference in Bias between a Reference Material and Clinical Samples.

A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator, trueness control, or external quality assessment sample based on the difference in bias between an RM and clinical samples (CSs) measured using 2 different measurement procedures (MPs). This difference in bias is compared with a criterion based on a medically relevant difference between an RM and CS results to make a conclusion regarding commutability. When more than 2 MPs are included, the commutability is assessed pairwise for all combinations of 2 MPs. This approach allows the same criterion to be used for all combinations of MPs included in the assessment. The assessment is based on an error model that allows estimation of various random and systematic sources of error, including those from sample-specific effects of interfering substances. An advantage of this approach is that the difference in bias between an RM and the average bias of CSs at the concentration (i.e., amount of substance present or quantity value) of the RM is determined and its uncertainty estimated. An RM is considered fit for purpose for those MPs for which commutability is demonstrated.