Evaluation of five multisteroid LC‒MS/MS methods used for routine clinical analysis: comparable performance was obtained for nine analytes

OBJECTIVES

A mass spectrometry (LC‒MS/MS)-based interlaboratory comparison study was performed for nine steroid analytes with five participating laboratories. The sample set contained 40 pooled samples of human serum generated from preanalyzed leftovers. To obtain a well-balanced distribution across reference intervals of each steroid, the leftovers first underwent a targeted mixing step.

METHODS

All participants measured a sample set once using their own multianalyte protocols and calibrators. Four participants used in-house developed measurement platforms, including IVD-CE certified calibrators, which were used by three participants; the 5th lab used the whole LC‒MS kit from an IVD manufacturer. All labs reported results for 17-hydroxyprogesterone, androstenedione, cortisol, and testosterone, and four labs reported results for 11-deoxycortisol, corticosterone, cortisone, dehydroepiandrosterone sulfate (DHEAS), and progesterone.

RESULTS

Good or acceptable overall comparability was found in Bland‒Altman and Passing‒Bablok analyses. Mean bias against the overall mean remained less than ±10 % except for DHEAS, androstenedione, and progesterone at one site and for cortisol and corticosterone at two sites (max. -18.9 % for androstenedione). The main analytical problems unraveled by this study included a bias not previously identified in proficiency testing, operator errors, non-supported matrix types and higher inaccuracy and imprecision at lower ends of measuring intervals.

CONCLUSIONS

This study shows that intermethod comparison is essential for monitoring the validity of an assay and should serve as an example of how external quality assessment could work in addition to organized proficiency testing schemes.

Clinical specificity of two assays for immunoglobulin kappa and lambda free light chains

OBJECTIVES

Free light chain (FLC) assays and the ratio of κ/λ are recommended for diagnosis, prognosis and monitoring of plasma cell dyscrasias (PCD). Limited data exists on FLC clinical specificity in patients diagnosed with other conditions.

METHODS

We assessed the κ, λ, and κ/λ FLC ratio using the FreeLite assay and the Sebia FLC ELISA assay in 176 patients with clinical presentations of fatigue, anemia, polyclonal hypergammaglobulinemia, joint disorders, kidney disease and non PCD-cancers with no monoclonal protein observed on serum protein electrophoresis or MASS-FIX immunoglobulin isotyping. Manufacturer defined reference intervals (RI) and glomerular filtration rate (GFR) specific RI (renal RI) were utilized.

RESULTS

For the κ/λ ratio, 68.7 % (121/176) of specimens on the FreeLite and 87.5 % (154/176) of specimens on the Sebia assay were within RI. For κ, 68.2 % (120/176) and 72.2 % (127/176) of results were outside RI for FreeLite and Sebia respectively. For λ, 37.5 % (66/176) and 84.1 % (148/176) of FreeLite and Sebia results were outside RI. With FreeLite and Sebia, patients with kidney disease (n=25) had the highest κ/λ ratios. 44 patients (25.0 %) had GFR <60 mL/min/BSA. When renal RI were applied, 13.6 % had a FLCr outside the renal RI with FreeLite, and 4.5 % with Sebia.

CONCLUSIONS

In a cohort of patients with signs and symptoms suggestive of PCDs, but ultimately diagnosed with other conditions, Sebia FLC had improved clinical specificity relative to FreeLite, if one was using an abnormal κ/λ ratio as a surrogate for monoclonality.

Evaluation of effects from hemoglobin variants on HbA1c measurements by different methods

OBJECTIVES

The impact of seven hemoglobin variants (Hb Q-Thailand, Hb G-Honolulu, Hb Ube-2, Hb New York, Hb J-Bangkok, Hb G-Coushatta, and Hb E) on the outcome of HbA1c was investigated for six methods by comparing with liquid chromatography-tandem mass spectrometry (LC/MS/MS) reference method.

METHODS

Twenty-nine normal and 112 variant samples were measured by LC/MS/MS, Sebia Capillarys 3 TERA, Intelligene Biosystems QuanTOF, Premier Hb9210, Arkray HA-8190V, Bio-Rad D-100, and Tosoh G11, then evaluated for correlation, consistency, and mean relative bias among six methods. The lowest biological variation bias of ±2.8 % was an acceptable standard.

RESULTS

All methods showed poor correlation and consistency with LC/MS/MS for Hb E. The unacceptable biases were observed for Capillarys 3 TERA (-14.4 to -3.7 % for Hb Q-Thailand, Hb Ube-2, Hb New York, Hb J-Bangkok and Hb E), QuanTOF (-8.3 to -2.9 % for Hb Ube-2, Hb New York and Hb G-Coushatta), Premier Hb9210 (-18.3 to -3.6 % for Hb Q-Thailand, Hb Ube-2, Hb New York, Hb J-Bangkok and Hb E), HA-8190V variant mode (-17.3 to 6.6 % for Hb G-Honolulu, Hb Ube-2, Hb New York, Hb G-Coushatta and Hb E). All variant samples showed larger biases than ±2.8 % comparing HA-8190V fast mode, D-100, and G11 with LC/MS/MS.

CONCLUSIONS

The accuracy of different HbA1c methods was influenced by some Hb variants, especially Hb Ube-2 and Hb New York. Thus, laboratories need to choose appropriate methods to measure HbA1c with different Hb variants.

Report of the International Council for Standardization in Haematology working group for standardization of reticulocyte parameters

INTRODUCTION

The International Council for Standardization in Haematology convened a working group to assess and propose improvements upon the state of standardization and harmonization of reticulocyte parameters among commercial hematology analyzers.

METHODS

An international group of laboratory hematologists prospectively collected and analyzed clinical samples using locally available IVD commercial hematology analyzers. Eight hundred and fifty-five total samples were collected at 6 sites using 9 distinct analyzer types. Samples were assessed for reticulocyte percent (RET%), immature reticulocyte fraction (IRF), and reticulocyte hemoglobin content (RHC). Method comparison and regression statistics were calculated. These analyses were used to determine whether statistical recalibration offered a potential avenue for increasing comparability between these methods.

RESULTS

While methods producing reticulocyte percent were the most comparable in this study, the state of harmonization for the IRF and RHC was reduced with pearson correlation coefficients ranging from 0.955 to 0.77 and 0.927 and 0.680, respectively. Nevertheless, use of parameters from the Passing Bablok regression substantially improved the comparability of the results. In addition, precision data was derived which also demonstrated substantial differences between analyzer systems.

CONCLUSION

While reticulocyte counting is correlated between the automated methods evaluated in this study, the current state of harmonization of other reticulocyte parameters is not as strong. A major challenge in moving this field forward is the need for commutable materials to facilitate comparisons between analyzers not co-located. A potential alternate approach to improve the current state would be instrument re-calibration. However, this is challenging both technically and due to national regulatory frameworks.

Statistical models for assessing agreement for quantitative data with heterogeneous random raters and replicate measurements

Agreement between methods for quantitative measurements are typically assessed by computing limits of agreement between pairs of methods and/or by illustration through Bland-Altman plots. We consider the situation where the observed measurement methods are considered a random sample from a population of possible methods, and discuss how the underlying linear mixed effects model can be extended to this situation. This is relevant when, for example, the methods represent raters/judges that are used to score specific individuals or items. In the case of random methods, we are not interested in estimates pertaining to the specific methods, but are instead interested in quantifying the variation between the methods actually involved making measurements, and accommodating this as an extra source of variation when generalizing to the clinical performance of a method. In the model we allow raters to have individual precision/skill and permit linked replicates (i.e., when the numbering, labeling or ordering of the replicates within items is important). Applications involving estimation of the limits of agreement for two datasets are shown: A dataset of spatial perception among a group of students as well as a dataset on consumer preference of French chocolate. The models are implemented in the MethComp package for R [Carstensen B, Gurrin L, Ekstrøm CT, Figurski M. MethComp: functions for analysis of agreement in method comparison studies; 2013. R package version 1.22, R Core Team. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2012].

Isolation and expansion of pure and functional γδ T cells

γδ T cells are important components of the immune system due to their ability to elicit a fast and strong response against infected and transformed cells. Because they can specifically and effectively kill target cells in an MHC independent fashion, there is great interest to utilize these cells in anti-tumor therapies where antigen presentation may be hampered. Since only a small fraction of T cells in the blood or tumor tissue are γδ T cells, they require extensive expansion to allow for fundamental, preclinical and ex vivo research. Although expansion protocols can be successful, most are based on depletion of other cell types rather than γδ T cell specific isolation, resulting in unpredictable purity of the isolated fraction. Moreover, the primary focus only lies with expansion of Vδ2+ T cells, while Vδ1+ T cells likewise have anti-tumor potential. Here, we investigated whether γδ T cells directly isolated from blood could be efficiently expanded while maintaining function. γδ T cell subsets were isolated using MACS separation, followed by FACS sorting, yielding >99% pure γδ T cells. Isolated Vδ1+ and Vδ2+ T cells could effectively expand immediately after isolation or upon freeze/thawing and reached expansion ratios between 200 to 2000-fold starting from varying numbers using cytokine supported feeder stimulations. MACS/FACS isolated and PHA stimulated γδ T cells expanded as good as immobilized antibody mediated stimulated cells in PBMCs, but delivered purer cells. After expansion, potential effector functions of γδ T cells were demonstrated by IFN-γ, TNF-α and granzyme B production upon PMA/ionomycin stimulation and effective killing capacity of multiple tumor cell lines was confirmed in killing assays. In conclusion, pure γδ T cells can productively be expanded while maintaining their anti-tumor effector functions against tumor cells. Moreover, γδ T cells could be expanded from low starting numbers suggesting that this protocol may even allow for expansion of cells extracted from tumor biopsies.

Comparing Clinical Accuracy and Analytical Accuracy Between Continuous Glucose Monitors

This study compares performance between two continuous glucose monitors (CGMs). The study design contains a mix of laboratory results (CGM vs YSI) and home results (CGM vs glucose meter). Analysis is provided for both clinical accuracy and analytical accuracy of CGM glucose measurements. Both types of accuracy are important. Error grid analysis informs about clinical accuracy. Analytical error is important as most users would prefer a CGM with a smaller spread of CGM versus reference differences. The authors provide the percentage of time that no result was obtained. Study design, data analysis, and editorial support were provided by a manufacturer of one of the products studied. This study provides a template for comparisons.

A review of Bland-Altman difference plot analysis in the veterinary clinical pathology laboratory

Current guidelines recommend using Bland-Altman plots (BA-plots), also called Difference plots, as part of method comparison evaluation in the veterinary clinical pathology laboratory. Analysis of differences can meaningfully augment linear regression techniques and allows fuller summarization of the performance of two methods relative to each other. This work summarizes the current literature on BA-plot composition and evaluation. Model data is used to demonstrate data evaluation approaches based on the observed differences, the combined inherent imprecision of the methods, and clinically relevant performance goals. Common limitations of the approaches, including points of frequent misinterpretation, are presented. BA-plot analysis can be part of an intentionally crafted method comparison study that provides analytically and clinically relevant data.

UHPLC-MS/MS for plasma lamotrigine analysis and comparison with a homogenous enzyme immunoassay

Aims: To develop and validate a UHPLC-MS/MS method for lamotrigine (LTG) analysis in human plasma and evaluate its agreement with a homogenous enzyme immunoassay (HEIA). Materials & methods: The UHPLC-MS/MS method was developed and validated according to the USFDA/EMA guidelines. A Bland-Altman plot was used to evaluate the agreement between UHPLC-MS/MS and HEIA. Results: Samples were pretreated with one-step protein precipitation and separated in 2.6 min. The intra- and inter-day bias and imprecisions were -15.8 to 15.0% and less than 11.17%, respectively. The recovery and matrix factor were 98.30 to 111.97%. The mean overestimation of UHPLC-MS/MS compared with HEIA was 21.57%. Conclusion: A rapid, sensitive and robust UHPLC-MS/MS method for plasma LTG analysis was developed and validated and was a 21.57% overestimation compared with HEIA.

Validation of the Sysmex XN-V Automated Nucleated Red Blood Cell Enumeration for Canine and Feline EDTA-Anticoagulated Blood

The enumeration of nRBCs (nucleated red blood cells) by manual counting is time-consuming and imprecise. As the first veterinary hematology analyzer, Sysmex XN-V provides automated nRBC counts. This study aimed to evaluate the performance of Sysmex XN-V in the enumeration of nRBCs for cats and dogs by comparing automated nRBC counts to manual counts from a total of 3810 canine and 2844 feline specimens. Repeatability, reproducibility, stability, carry-over, and linearity were assessed. The repeatability and reproducibility of Sysmex XN-V were good, with mean coefficients of variation (CV) of 4.5% and 5.4%, respectively. Bland-Altman difference analysis revealed mean biases shown as nRBCs/100 WBCs of 0.01 in dogs and 0.11 in cats with low nRBCs (<5/100 WBCs), mean biases of -1.27 in dogs and -0.24 in cats with moderate nRBC counts (5-20 nRBCs/100 WBCs), and mean biases of -7.76 in dogs and -1.31 in cats with high nRBC counts (>20 nRBCs/100 WBCs). The total observable error was below 9% in both species and at all ranges. Overall concordance between methods was high (91% in canine and 93% in feline samples). The automated nRBC count by Sysmex XN-V was found to be accurate and precise and can replace manual counts for cat and dog samples. Non-statistical quality assurance by scattergram evaluation, re-gating, and confirmation by blood smear evaluation is, however, recommended, especially in cases with severe normoblastosis. This advancement will save time, reduce errors, and add prognostic value to hematological results for animal patients.

Comparison and commutability study among four faecal immunochemical tests (FIT) systems

OBJECTIVES

Faecal immunochemical tests for haemoglobin (FIT) are used in colorectal cancer screening programs around the world and increasingly for triage of symptomatic patients. FIT results are currently not traceable to a common reference standard and results obtained on various FIT systems may not be equivalent. The size of the bias between the systems is difficult to quantify due to the complex pre-analytical aspects of FIT.

METHODS

This study aimed to quantify the bias and the correlation between four FIT systems by measuring a panel of 38 faecal samples while limiting the effect of the pre-analytical aspects. In addition, the commutability of seven candidate reference materials (RM) was assessed.

RESULTS

Pairwise method comparisons based on faecal samples demonstrated Pearson correlation coefficients ranging between 0.944 and 0.970 and an average proportional bias of -30 to -35 % for one FIT system compared to the other three. The relative standard deviation among biases of the individual samples was around 20 %. Due to these sample specific differences, no decisive conclusions could be drawn in the commutability study. However, two candidate RMs, prepared in the FIT system-specific storage/extraction buffers, had a better commutable profile than the other five.

CONCLUSIONS

The use of a common threshold for all FIT systems is currently not possible due to the presence of a proportional bias. We have identified potential commutable RMs to take to further studies on the production of a common calibrator, with the aim being to reduce the analytical bias observed on different FIT systems.

Validation of the Hem-Col capillary blood collection system for routine laboratory analyses

At home collection of capillary blood using Hem-Col tubes (Labonovum) could offer a solution to patients with chronic conditions, who require frequent laboratory analyses. The collection tubes contain a conservation buffer to stabilize analytes for up to 5 days. In this validation study it was investigated whether analytes are measured accurately in Hem-Col tubes 5 days after collection. Forty-six healthy volunteers donated blood via venepuncture as well as capillary blood by finger prick using Hem-Col tubes. The analytes were measured within 2 h for the venepuncture and after 120 h for the Hem-Col method. The results of each analyte were analysed using Passing-Bablok regression analyses. The analytes that met the predefined acceptance criteria were total cholesterol, LDL-cholesterol, thyroid stimulating hormone (TSH) and glycated haemoglobin (HbA1c). HDL-cholesterol, C-reactive protein (CRP), ferritin, bilirubin total, creatinine, gGT and triglycerides met two out of three acceptance criteria. All other analytes did not meet the predefined criteria. The Hem-Col method is suitable for the measurement of total cholesterol, LDL-cholesterol, thyroid stimulating hormone (TSH) and glycated haemoglobin (HbA1c). However, due to this limited set of valid tests and practical limitations, routine application of this novel collection system in daily practice is limited.

Assessing the agreement between the pneumatic and the flow-centrifuge method for estimating xylem safety in temperate diffuse-porous tree species

The increasing frequency of global change-type droughts has created a need for fast, accurate and widely applicable techniques for estimating xylem embolism resistance to improve forecasts of future forest changes. We used data from 12 diffuse-porous temperate tree species covering a wide range of xylem safety to compare the pneumatic and flow-centrifuge method, two rapid methods used for constructing xylem vulnerability curves. We evaluated the agreement between parameters estimated with both methods and the sensitivity of pneumatic measurements to the duration of air discharge (AD) measurements. There was close agreement between xylem water potentials at 50% air discharged (PAD), estimated with the Pneumatron, and 50% loss of hydraulic conductivity (PLC), estimated with the flow-centrifuge method (mean signed deviation: 0.12 MPa, Pearson correlation: 0.96 after 15 s of gas extraction). However, the relationship between the estimated slopes was more variable, resulting in lower agreement in the xylem water potential at 12% and 88% PAD/PLC. The agreement between the two methods was not affected by species-specific vessel length distributions. All pneumatic parameters were sensitive to AD time. Overall agreement was highest at relatively short AD times, with an optimum at 16 s. Our results highlight the value of the Pneumatron as an easy and reliable tool to estimate 50% embolism thresholds for a wide range of diffuse-porous temperate angiosperms. Further, our study provides a set of useful metrics for methodological comparisons of vulnerability curves in terms of systematic and random deviations, as well as overall agreement.

Evaluation of the rapid Quidel Sofia Lyme fluorescent immunoassay as a first-tier test in a modified 2-tier testing algorithm for Lyme disease: A comparison with the Zeus ELISA Borrelia VlsE1/pepC10 lgG/IgM assay followed by the Zeus monovalent IgM/IgG confirmatory assay

OBJECTIVES

Recently modified 2-tier testing (MTTT) algorithms using 2 enzyme immunoassays (EIAs) as opposed to an EIA followed by immunoblot have been approved by the US Food and Drug Administration (FDA) for the screening and confirmation of Lyme disease. The Quidel Sofia Lyme fluorescent immunoassay is a rapid lateral-flow method that can be performed in real time, permitting on-demand testing. We evaluated the performance of the Sofia assay as a first-tier test in an MTTT algorithm.

METHODS

We compared the Sofia Lyme test with the Zeus ELISA Borrelia VlsE1/pepC10 lgG/IgM test, followed by the Zeus monovalent IgM/IgG EIA as the confirmatory test.

RESULTS

When used as a first-tier test compared with a standard Zeus MTTT assay, the positive percentage agreement was 91.4%% (95% CI, 77.6%-97.0%). The negative percentage agreement was 100% (95% CI, 94.0%-100%). The overall agreement was 98.3% (95% CI, 94.2%-99.4%). κ = 0.945, indicating "almost perfect agreement."

CONCLUSIONS

The Sofia Lyme test performs well compared with an FDA-approved MTTT.

Albumin determined by bromocresol green leads to erroneous results in routine evaluation of patients with chronic kidney disease

OBJECTIVES

Measurement of plasma albumin is pivotal for clinical decision-making in patients with chronic kidney disease (CKD). Routinely used methods as bromocresol green (BCG) and bromocresol purple (BCP) can suffer from aselectivity, but the impact of aselectivity on the accuracy of plasma albumin results of CKD-patients is still unknown. Therefore, we evaluated the performance of BCG-, BCP- and JCTLM-endorsed immunological methods in patients with various stages of CKD.

METHODS

We evaluated the performance of commonly used albumin methods in patients with CKD stages G1 through G5, the latter divided in two groups based on whether they received hemodialysis treatment. In total, 163 patient plasma samples were measured at 14 laboratories, on six different BCG and BCP-platforms, and four different immunological platforms. The results were compared with an ERM-DA-470k-corrected nephelometric assay. The implications on outcome is evaluated by the proportion of patient results <38 g/L for the diagnosis of protein energy wasting.

RESULTS

Albumin results determined with BCP- and immunological methods showed the best agreement with the target value (92.7 and 86.2 %, respectively vs. 66.7 % for BCG, namely due to overestimation). The relative agreement of each method with the target value was platform-dependent, with larger variability in agreement between platforms noted for BCG and immunological methods (3.2-4.6 and 2.6-5.3 %) as opposed to BCP (0.7-1.5 %). The stage of CKD had similar effects on the variability in agreement for the three method-groups (0.6-1.8 % vs. 0.7-1.5 % vs. 0.4-1.6 %). The differences between methods cause discrepancies in clinical decision-making, as structurally fewer patients were diagnosed with protein energy wasting upon using BCG-based albumin results.

CONCLUSIONS

Our study shows that BCP is fit for the intended use to measure plasma albumin levels in CKD patients from all stages, including patients on hemodialysis. In contrast, most BCG-based platforms falsely overestimate the plasma albumin concentration.

Impact of Variation between Assays and Reference Intervals in the Diagnosis of Endocrine Disorders

Method-related variations in the measurement of hormones and the reference intervals used in the clinical laboratory can have a significant, but often under-appreciated, impact on the diagnosis and management of endocrine disorders. This variation in laboratory practice has the potential to lead to an errant approach to patient care and thus could cause harm. It may also be the source of confusion or result in excessive or inadequate investigation. It is important that laboratory professionals and clinicians know about these impacts, their sources, and how to detect and mitigate them when they do arise. In this review article, we describe the historical and scientific context from which inconsistency in the clinical laboratory arises. Examples from the published literature of the impact of the method, reference interval, and clinical decision threshold-related discordances on the assessment and monitoring of various endocrine disorders are discussed to illustrate the sources, causes, and effects of this variability. Its potential impact on the evaluation of growth hormone deficiency and excess, thyroid and parathyroid disorders, hyperandrogenism, hypogonadism, glucocorticoid excess and deficiency, and diabetes mellitus is elaborated. Strategies for assessment and mitigation of the discordance are discussed. The clinical laboratory has a responsibility to recognise and address these issues, and although a lot has been accomplished in this area already, there remains more to be done.

Impact on result interpretation of correct and incorrect selection of veterinary glucometer canine and feline settings

Veterinary glucometers should be correctly coded for the patient species; however, coding errors occur in clinical settings and the impact of such errors has not been characterized. We compared glucose concentrations in 127 canine and 37 feline samples using both canine and feline settings on a veterinary glucometer (AlphaTrak; Zoetis). All samples were measured first on the canine setting and then measured using the feline setting. Glucose concentration was also measured using a central laboratory biochemical analyzer (Cobas c311; Roche). Three data comparisons for each species were investigated: incorrectly coded glucometer vs. correctly coded glucometer, correctly coded glucometer vs. Cobas c311, and incorrectly coded glucometer vs. Cobas c311. For each comparison, the following analyses were conducted: Spearman rank correlation coefficient, Bland-Altman difference plot analysis, mountain plot analysis, and Deming regression. For clinical context, Clarke error grids were constructed. There was high positive correlation for all comparisons with both species. For all comparisons, mean difference was low (-0.7 to 0.5 mmol/L for canine samples, 1.0-2.0 mmol/L for feline samples). Incorrect glucometer coding resulted in proportional bias for canine samples and positive constant bias for feline samples, and individual differences could be large (-4.44 mmol/L for one dog, 6.16 mmol/L for one cat). Although the glucometer should be used per the manufacturer's recommendation, coding errors are unlikely to have severe adverse clinical consequences for most patients based on error grid analysis.

Evaluation of canine and feline leukocyte differential counts obtained with the scil vCell 5 compared to the Advia 2120 hematology analyzer and a manual method

The vCell 5 (scil Animal Care), a point-of-care hematology analyzer (POCA), was recently introduced to veterinary laboratories. This laser- and impedance-based analyzer is capable of providing a CBC with 5-part WBC differential count (Diff) along with WBC cytograms and flags serving as interpretation aids for numerical results. We compared the scil POCA-Diff to reference methods (i.e., manual differential count, Advia 2120 hematology analyzer [Siemens]) for canine and feline blood samples and considered WBC cytograms and flags. Total observed error (TEo), calculated from CV and bias%, was compared to total allowable error (TEa). Data were analyzed before and after a review process (exclusion of flagged and samples with invalid cytograms). For both species, correlation was good-to-excellent (rs = 0.81-0.97) between both analyzers for all variables, except for feline monocytes (rs = 0.21-0.63) and canine monocyte% (rs = 0.50). Smallest biases were seen for neutrophils (dog: -5.7 to 0.8%; cat: 1.5-9.4%) with both reference methods. Quality requirements (TEo < TEa) were fulfilled for canine and feline neutrophils (TEo = 5.3-10.6%, TEa = 15%) and eosinophils (TEo = 67.1-83%, TEa = (90)-50%) considering at least one reference method. Our review process led to mildly higher rs-values for most variables. Although not completely satisfactory, the scil POCA provides reliable results in compliance with ASVCP quality goals for canine and feline neutrophils and eosinophils. Analyzer flag and cytogram analysis served as useful tools for QA, indicating the necessity for manual review of blood smears, and contributed to improvement of scil POCA performance.

Influence of preanalytical and analytical factors on the quantification of six regulatory serum proteins

Background: We analyzed differences in protein concentrations in human blood serum depending on the tube material and the immunoassay platform used. Materials & methods: Blood samples from study participants were collected in glass and polypropylene tubes (n = 292). Serum concentrations of six proteins (BDNF, IGF-1, VEGF-A, TGF-β1, MCP-1 and IL-18) were assessed by using ELISAs (all biomarkers), as well as a novel fully automated immunoassay platform (all but IGF-1, n = 211). Bland-Altman analyses were conducted to investigate intrasample variability of protein concentrations. Results: Tube comparison resulted in mean biases of between -0.45 and -70.64%. Platform comparison revealed mean biases of between 21.04 and -128.10%. Conclusion: Protein concentrations can vary significantly depending on the types of tube and immunoassay used, with protein-specific differences.

Evaluation of two fully automated ADAMTS13 activity assays in comparison to manual FRET assay

INTRODUCTION

The objective of the present study was to evaluate and compare the validity and utility of two fully automated ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity assays for clinical diagnostic decision-making and to compare their performance.

METHODS

Two automated ADAMTS13 activity assays (Werfen HemosIL® AcuStar ADAMTS13 Activity, Technoclone Technofluor ADAMTS13 Activity) were compared with a manual FRET assay (BioMedica ACTIFLUOR ADAMTS13 Activity). The following samples were used: 13 acute phase TTP (thrombotic thrombocytopenic purpura) samples from 11 different patients, one sample from a patient with congenital ADAMTS13 deficiency, 16 samples from control patients, three follow-up samples from TTP patients in long-term remission and one sample from a patient with stem cell transplantation related thrombotic microangiopathy (TMA). The WHO 1st International Standard for ADAMTS13 and several dilutions of normal plasma with ADAMTS13-depleted normal plasma were also tested. Statistical analysis included descriptive statistics, sensitivity and specificity, Passing & Bablok regression and Bland-Altman plot.

RESULTS

The quantitative comparison between the HemosIL® (x) and Technofluor (y) methods showed a strong correlation (Pearson r = 0.98, n = 49). When considering an ADAMTS13 activity of <10% as a hallmark for the diagnosis of TTP, two fully automated assays were both able to identify all TTP- and non-TTP-samples correctly, resulting in sensitivities and specificities of 100%.

CONCLUSION

Both fully automated ADAMTS13 activity assays showed a good diagnostic performance and quantitative correlation among themselves, discriminating reliably between TTP- and non-TTP-patients.

How low can we (reliably) go? A method comparison of thyroid-stimulating hormone assays with a focus on low concentrations

Objective

International guidelines concerning subclinical hyperthyroidism and thyroid cancer advice absolute cut-off values for aiding clinical decisions in the low range of thyroid-stimulating hormone (TSH) concentrations. As TSH assays are known to be poorly standardized in the normal to high range, we performed a TSH assay method comparison focusing on the low range.

Methods

Sixty samples, selected to cover a wide range of TSH concentrations (<0.01 to 120 mIU/L) with oversampling in the lower range (<0.4 mIU/L), were used for the method comparison between three TSH immunoassays (Cobas, Alinity and Atellica). In addition, 20 samples were used to assess the coefficient of variation from duplicate measurements in these three methods.

Results

The TSH immunoassays showed standardization differences with a bias of 7-16% for the total range and 1-14% for the low range. This could lead to a different classification of 1.5% of all measured TSH concentrations <0.40 mIU/L measured in our laboratory over the last 6 months, regarding the clinically important cut-off value of TSH = 0.1 mIU/L. As the imprecision of the immunoassays varied from 1.6-5.5%, this could lead to a similar reclassification as the bias between immunoassays.

Conclusions

We established the standardization differences of frequently used TSH assays for the total and low concentration ranges. Based on the proportional bias and the imprecision, this effect seems to have limited clinical consequences for the low TSH concentration range. Nevertheless, as guidelines mention absolute TSH values to guide clinical decision-making, caution must be applied when interpreting values close to these cut-offs.

Method Comparison and Clinical Performance of Breast Cancer Tumor Markers on Novel Multiplex Immunoassay and Automatized LOCI Technology Platforms

Tumor marker determinations are valuable tools for the guidance of breast cancer patients during the course of disease. They are assessed on diverse analytical platforms that may be associated with differences according to the methods applied and the clinical performance. To investigate the method dependency and clinical significance of breast cancer protein tumor markers, CEA, CA 15-3, CA 125, CA 19-9 and AFP were measured in a total of 154 biobanked samples from 77 patients with breast cancer, 10 with DCIS, 31 with benign breast diseases and 36 healthy controls using a Millipore multiplex biomarker panel (MP) and an automized version of the routinely used Vista LOCI technology. The markers were compared between methods and investigated for diagnostic performance. CEA, CA 15-3 and AFP showed good correlations between both platforms with correlation coefficients of R = 0.85, 0.85 and 0.92, respectively, in all samples, but similarly also in the various subgroups. CA 125 and CA 19-9 showed only moderate correlations (R = 0.71 and 0.56, respectively). Absolute values were significantly higher for CEA, CA 15-3, CA 125 and AFP in the Vista LOCI as compared with the MP method and vice versa for CA 19-9. The diagnostic performance for discrimination of breast cancer from healthy controls was similar for both methods with AUCs in ROC curves for CEA (MP 0.81, 95% CI 0.72-0.91; LOCI 0.81; 95% CI 0.72-0.91) and CA-15-3 (MP 0.75, 95% CI 0.65-0.86; LOCI 0.67, 95% CI 0.54-0.79). Similar results were obtained for the comparison of breast cancer with benign breast diseases regarding CEA (AUC MP 0.62, 95% CI 0.51-0.73; LOCI 0.64, 95% CI 0.53-0.74) and CA-15-3 (MP 0.70, 95% CI 0.6-0.81; LOCI 0.66, 95% CI 0.54-0.77). Both platforms show moderate to good method comparability for tumor markers with similar clinical performance. However, absolute levels in individual patients should be interpreted with care.

Poor comparability of plasma renin activity measurement in determining patient samples: the status quo and recommendations for harmonization

OBJECTIVES

This study aims to investigate and update the consistency and comparability of plasma renin activity (PRA) assays in measuring clinical samples. The contributions of recalibration, blank subtraction, and incubation strategies to interchangeability were also explored.

METHODS

Five different laboratories were evaluated using forty-six individual plasma samples, including four liquid chromatography-tandem mass spectrometry (LC‒MS/MS) assays and one chemiluminescence immunoassay (CLIA). Spearman correlation coefficient (R), Passing-Bablok regression, and Bland‒Altman plot analyses were used to evaluate the consistency among assays. Consistency before and after recalibration, blank subtraction, and incubation strategy unification was compared.

RESULTS

A good correlation was observed among all assays (R>0.93). None of the samples measured by all assays showed coefficient variation (CV) <10 %, and 37 % of samples showed overall CVs >20 %. The 95 % confidence intervals (CIs) for slopes did not contain 1 for most assay pairs. Large relative biases (-85.1-104.2 %) were found, and 76 % (52-93 %) of samples had unacceptable biases. Recalibration reduced the calibration bias. Ignoring blank subtraction improved the comparability across all assays while unifying incubation did not.

CONCLUSIONS

The interchangeability of PRA measurement was unsatisfying. Harmonization on calibrator and ignoring blank were recommended. Unifying incubation strategy was unnecessary.

Salivary cortisol and cortisone in diagnosis of Cushing's syndrome - a comparison of six different analytical methods

OBJECTIVES

Salivary cortisol and cortisone at late night and after dexamethasone suppression test (DST) are increasingly used for screening of Cushing's syndrome (CS). We aimed to establish reference intervals for salivary cortisol and cortisone with three liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques and for salivary cortisol with three immunoassays (IAs), and evaluate their diagnostic accuracy for CS.

METHODS

Salivary samples at 08:00 h, 23:00 h and 08:00 h after a 1-mg DST were collected from a reference population (n=155) and patients with CS (n=22). Sample aliquots were analyzed by three LC-MS/MS and three IA methods. After establishing reference intervals, the upper reference limit (URL) for each method was used to calculate sensitivity and specificity for CS. Diagnostic accuracy was evaluated by comparing ROC curves.

RESULTS

URLs for salivary cortisol at 23:00 h were similar for the LC-MS/MS methods (3.4-3.9 nmol/L), but varied between IAs: Roche (5.8 nmol/L), Salimetrics (4.3 nmol/L), Cisbio (21.6 nmol/L). Corresponding URLs after DST were 0.7-1.0, and 2.4, 4.0 and 5.4 nmol/L, respectively. Salivary cortisone URLs were 13.5-16.6 nmol/L at 23:00 h and 3.0-3.5 nmol/L at 08:00 h after DST. All methods had ROC AUCs ≥0.96.

CONCLUSIONS

We present robust reference intervals for salivary cortisol and cortisone at 08:00 h, 23:00 h and 08:00 h after DST for several clinically used methods. The similarities between LC-MS/MS methods allows for direct comparison of absolute values. Diagnostic accuracy for CS was high for all salivary cortisol and cortisone LC-MS/MS methods and salivary cortisol IAs evaluated.

Preliminary assessment of serum capillary zone electrophoresis in the Asian elephant (Elephas maximus)

Serum protein electrophoresis has been demonstrated to have utility in diagnostic workup, wellness exams, and prognosis. Agarose gel electrophoresis (AGE) has previously been described for use with serum from Asian elephants (Elephas maximus). As the newer method of capillary zone electrophoresis (CZE) is becoming more commonplace in veterinary diagnostic laboratories, serum samples from Asian elephants were examined using this method. CZE allowed for a reproducible definition of two beta fractions and, overall, showed a low coefficient of variation for fraction quantitation. Preliminary reference intervals were generated using samples primarily from an older population of 22 female elephants. Albumin levels determined by CZE were also compared with those determined by the bromocresol green method on a chemistry analyzer. It was found that the latter method overestimated the level of albumin with a mean positive bias of 11.6% or 0.38 g/dL, thus method-specific reference intervals should be used. Significant negative correlations were observed between A/G ratio determined by CZE and serum amyloid A levels (r = -0.47, p < 0.0001) and haptoglobin (r = -0.52, p < 0.0001); both APP were significantly correlated with the alpha 2 globulin fraction (p < 0.0001). CZE reflects an overall picture of changes in acute phase proteins and immunoglobulins and accurate quantitation of albumin and thus should be considered as an adjunct tool to the use of other measures of the acute phase response in patient monitoring.

Evaluating the Efficiency of the Cobas 6800 System for BK Virus Detection in Plasma and Urine Samples

We evaluated the overall performance of the Cobas 6800 BKV test in detecting BK virus (BKV). We examined the imprecision of the Cobas 6800 BKV test and compared the qualitative and quantitative results obtained from the Cobas 6800 BKV test and the Real-Q BKV quantification assay. We assessed 88 plasma and 26 urine samples collected between September and November 2022 from patients with BKV infection using the Real-Q BKV quantitative assay. The lognormal coefficient of variation indicated that the inter-assay precision of the Cobas 6800 BKV test ranged from 13.86 to 33.83%. A strong correlation was observed between the quantitative results obtained using the Cobas 6800 BKV test and the Real-Q BKV quantification assay for plasma samples. The Spearman's rank correlation coefficients (ρ) for plasma, polymerase chain reaction (PCR) media-stabilized urine, and raw urine samples were 0.939, 0.874, and 0.888, respectively. Our analyses suggest that the Cobas 6800 BKV test is suitable for clinical applications owing to the strong correlation between the results obtained using this test and the Real-Q BKV quantification assay in plasma and urine samples. Furthermore, utilizing fresh raw urine samples can be a viable approach for the Cobas 6800 BKV test as it is less labor- and time-intensive.

Predicting whether patients will achieve minimal clinically important differences following hip or knee arthroplasty

Aims

A substantial fraction of patients undergoing knee arthroplasty (KA) or hip arthroplasty (HA) do not achieve an improvement as high as the minimal clinically important difference (MCID), i.e. do not achieve a meaningful improvement. Using three patient-reported outcome measures (PROMs), our aim was: 1) to assess machine learning (ML), the simple pre-surgery PROM score, and logistic-regression (LR)-derived performance in their prediction of whether patients undergoing HA or KA achieve an improvement as high or higher than a calculated MCID; and 2) to test whether ML is able to outperform LR or pre-surgery PROM scores in predictive performance.

Methods

MCIDs were derived using the change difference method in a sample of 1,843 HA and 1,546 KA patients. An artificial neural network, a gradient boosting machine, least absolute shrinkage and selection operator (LASSO) regression, ridge regression, elastic net, random forest, LR, and pre-surgery PROM scores were applied to predict MCID for the following PROMs: EuroQol five-dimension, five-level questionnaire (EQ-5D-5L), EQ visual analogue scale (EQ-VAS), Hip disability and Osteoarthritis Outcome Score-Physical Function Short-form (HOOS-PS), and Knee injury and Osteoarthritis Outcome Score-Physical Function Short-form (KOOS-PS).

Results

Predictive performance of the best models per outcome ranged from 0.71 for HOOS-PS to 0.84 for EQ-VAS (HA sample). ML statistically significantly outperformed LR and pre-surgery PROM scores in two out of six cases.

Conclusion

MCIDs can be predicted with reasonable performance. ML was able to outperform traditional methods, although only in a minority of cases.

Effect of storage temperature and time on measurement of serum symmetric dimethylarginine concentration using point-of-care and commercial laboratory analyzers in cats and dogs

BACKGROUND

Stability of serum symmetric dimethylarginine (sSDMA) during short- and long-term storage has not been assessed for the immunoassay of the Point-of-Care IDEXX Catalyst DX (POC) analyzer and the Enzyme Multiplied Immunoassay Technique of IDEXX commercial laboratory (CL). Also, the agreement between both analyzers is questioned.

OBJECTIVES

To determine (a) the effect of storage time and temperature on sSDMA measured by POC and CL; (b) the agreement between sSDMA measured by POC and CL; and (c) the imprecision of the POC.

ANIMALS

Serum of cats (n = 17) and dogs (n = 18) with a range of SDMA concentrations (6 to >100 μg/dL).

METHODS

Based on an equivalence trial with predefined equivalence range (-3.0 to +3.0 μg/dL) and using T0 as baseline, stability was evaluated after 24 hours at 22°C and 4°C (POC); after 7 days at 4°C (POC and CL) and after 10 and 24 months at -24°C and -80°C (CL). Bland-Altman plots enabled method comparison. Imprecision of the POC was assessed by duplicate sSDMA measurements at T0.

RESULTS

The POC analyzer produced equivalent sSDMA measurements if samples were stored for 24 hours at 4°C (95% confidence interval [CI]: -2.5-2.0 μg/dL), but not when stored for 24 hours at room temperature (RT; 95% CI: -4.1 to 0.5 μg/dL) or after 7 days at 4°C (95% CI: -3.6-1.0 μg/dL). The CL analyzer was less affected by preanalytical variation with clinically similar results obtained when samples were stored for 7 days at 4°C (95% CI: -2.2 to 2.4 μg/dL) and for at least 24 months at -24°C (95% CI: -1.7 to 2.9 μg/dL) and -80°C (95% CI: -1.5 to 3 μg/dL). A relevant mean difference of -2.3 μg/dL between both analyzers was found. Duplicate POC measurements were equivalent (95% CI: -2.6 to 2.0 μg/dL).

CONCLUSIONS

Delayed analysis may significantly change sSDMA depending on storage and measurement conditions. Interchangeable use of assays should be done with caution because analytical variation could be interpreted as clinically relevant change.

Mouse Model of Fragile X Syndrome Analyzed by Quantitative Proteomics: A Comparison of Methods

Multiple methods for quantitative proteomics are available for proteome profiling. It is unclear which methods are most useful in situations involving deep proteome profiling and the detection of subtle distortions in the proteome. Here, we compared the performance of seven different strategies in the analysis of a mouse model of Fragile X Syndrome, involving the knockout of the fmr1 gene that is the leading cause of autism spectrum disorder. Focusing on the cerebellum, we show that data-independent acquisition (DIA) and the tandem mass tag (TMT)-based real-time search method (RTS) generated the most informative profiles, generating 334 and 329 significantly altered proteins, respectively, although the latter still suffered from ratio compression. Label-free methods such as BoxCar and a conventional data-dependent acquisition were too noisy to generate a reliable profile, while TMT methods that do not invoke RTS showed a suppressed dynamic range. The TMT method using the TMTpro reagents together with complementary ion quantification (ProC) overcomes ratio compression, but current limitations in ion detection reduce sensitivity. Overall, both DIA and RTS uncovered known regulators of the syndrome and detected alterations in calcium signaling pathways that are consistent with calcium deregulation recently observed in imaging studies. Data are available via ProteomeXchange with the identifier PXD039885.

Comparison of colorimetric, fluorometric, and liquid chromatography-mass spectrometry assays for acetyl-coenzyme A

Acetyl-Coenzyme A is a central metabolite in catabolic and anabolic pathways as well as the acyl donor for acetylation reactions. Multiple quantitative measurement techniques for acetyl-CoA have been reported, including commercially available kits. Comparisons between techniques for acetyl-CoA measurement have not been reported. This lack of comparability between assays makes context-specific assay selection and interpretation of results reporting changes in acetyl-CoA metabolism difficult. We compared commercially available colorimetric ELISA and fluorometric enzymatic-based kits to liquid chromatography-mass spectrometry-based assays using tandem mass spectrometry (LC-MS/MS) and high-resolution mass spectrometry (LC-HRMS). The colorimetric ELISA kit did not produce interpretable results even with commercially available pure standards. The fluorometric enzymatic kit produced comparable results to the LC-MS-based assays depending on matrix and extraction. LC-MS/MS and LC-HRMS assays produced well-aligned results, especially when incorporating stable isotope-labeled internal standards. In addition, we demonstrated the multiplexing capability of the LC-HRMS assay by measuring a suite of short-chain acyl-CoAs in a variety of acute myeloid leukemia cell lines and patient cells.

Comparison of Morphological Sex Assessment and Genetic Sex Determination on Adult and Sub-Adult 17th-19th Century Skeletal Remains

The first step in the analysis of human skeletal remains is the establishment of the biological profile of an individual. This includes sex assessment, which depends highly on the age of the individual and on the completeness and preservation state of the remains. Macroscopic methods only provide the assessment of sex, while for sex determination, molecular methods need to be included. However, poor preservation of the remains can make molecular methods impossible and only assessment can be performed. Presented research compares DNA-determined and morphologically assessed sex of adult and non-adult individuals buried in a modern-age cemetery (17th to late 19th century) in Ljubljana, Slovenia. The aim of the study was to assess the accuracy of commonly used macroscopic methods for sex assessment on a Slovenian post-medieval population. Results demonstrate that for adults, macroscopic methods employed are highly reliable and pelvic morphology, even the sciatic notch alone, is more reliable than skull. In non-adults, macroscopic methods are not as reliable as in adults, which agrees with previous research. This study shows how morphological and molecular methods can go hand in hand when building a biological profile of an individual. On their own, each methodology presented some individuals with undetermined sex, while together, sex of all the individuals was provided. Results confirm suitability of sex assessment based on skull and especially pelvic morphology in Slovenian post-medieval adults, while in the non-adult population molecular methods are advised.

Comparing the results from a Swedish pregnancy cohort using data from three automated placental growth factor immunoassay platforms intended for first-trimester preeclampsia prediction

INTRODUCTION

Risk evaluation for preeclampsia in early pregnancy allows identification of women at high risk. Prediction models for preeclampsia often include circulating concentrations of placental growth factor (PlGF); however, the models are usually limited to a specific PlGF method of analysis. The aim of this study was to compare three different PlGF methods of analysis in a Swedish cohort to assess their convergent validity and appropriateness for use in preeclampsia risk prediction models in the first trimester of pregnancy.

MATERIAL AND METHODS

First-trimester blood samples were collected in gestational week 11⁺⁰ to 13⁺⁶ from 150 pregnant women at Uppsala University Hospital during November 2018 until November 2020. These samples were analyzed using the different PlGF methods from Perkin Elmer, Roche Diagnostics, and Thermo Fisher Scientific.

RESULTS

There were strong correlations between the PlGF results obtained with the three methods, but the slopes of the correlations clearly differed from 1.0: PlGF_PerkinElmer  = 0.553 (95% confidence interval [CI] 0.518-0.588) * PlGF_Roche -1.112 (95% CI -2.773 to 0.550); r = 0.966, mean difference -24.6 (95% CI -26.4 to -22.8). PlGF_PerkinElmer  = 0.673 (95% CI 0.618-0.729) * PlGF_ThermoFisher -0.199 (95% CI -2.292 to 1.894); r = 0.945, mean difference -13.8 (95% CI -15.1 to -12.6). PlGF_Roche  = 1.809 (95% CI 1.694-1.923) * PlGF_PerkinElmer +2.010 (95% CI -0.877 to 4.897); r = 0.966, mean difference 24.6 (95% CI 22.8-26.4). PlGF_Roche  = 1.237 (95% CI 1.113-1.361) * PlGF_ThermoFisher +0.840 (95% CI -3.684 to 5.363); r = 0.937, mean difference 10.8 (95% CI 9.4-12.1). PlGF_ThermoFisher  = 1.485 (95% CI 1.363-1.607) * PlGF_PerkinElmer +0.296 (95% CI -2.784 to 3.375); r = 0.945, mean difference 13.8 (95% CI 12.6-15.1). PlGF_ThermoFisher  = 0.808 (95% CI 0.726-0.891) * PlGF_Roche -0.679 (95% CI -4.456 to 3.099); r = 0.937, mean difference -10.8 (95% CI -12.1 to -9.4).

CONCLUSION

The three PlGF methods have different calibrations. This is most likely due to the lack of an internationally accepted reference material for PlGF. Despite different calibrations, the Deming regression analysis indicated good agreement between the three methods, which suggests that results from one method may be converted to the others and hence used in first-trimester prediction models for preeclampsia.

Detection of Choroidal Neovascularization Using Optical Tissue Transparency

Purpose

Optical tissue transparency (OTT) provides a tool for visualizing the entire tissue block. This study provides insights into the potential value of OTT with light-sheet fluorescence microscopy (LSFM) in detecting choroidal neovascularization (CNV) lesions.

Methods

OTT with LSFM, hematoxylin and eosin (H&E) staining of paraffin sections, choroidal flatmount immunofluorescence, and optical coherence tomography angiography (OCTA) were used to obtain images of CNV. We determined the rate of change as (Data of week 1 - Data of week 2)/Data of week 1 × 100%. Finally, we compared the rate of change acquired from OTT with LSFM and the other methodologies.

Results

We found that OTT with LSFM can realize three-dimensional (3D) visualizations of the entire CNV. The results showed that the decline in the rate of change from week 1 to week 2 after laser photocoagulation was 33.05% with OTT, 53.01% with H&E staining, 48.11% with choroidal flatmount, 24.06% with OCTA (B-scan), 18.08% with OCTA (en face), 10.98% with OCTA (3D reconstruction), and 7.74% with OCTA (vessel diameter index).

Conclusions

OTT with LSFM will continue to be an invaluable resource for investigators to detect more visualized and quantified information regarding CNV.

Translational Relevance

OTT with LSFM now serves as a tool for detecting CNV in mice, and it may undergo human clinical trials in the future.

Precision oncology: a review to assess interpretability in several explainable methods

Great efforts have been made to develop precision medicine-based treatments using machine learning. In this field, where the goal is to provide the optimal treatment for each patient based on his/her medical history and genomic characteristics, it is not sufficient to make excellent predictions. The challenge is to understand and trust the model's decisions while also being able to easily implement it. However, one of the issues with machine learning algorithms-particularly deep learning-is their lack of interpretability. This review compares six different machine learning methods to provide guidance for defining interpretability by focusing on accuracy, multi-omics capability, explainability and implementability. Our selection of algorithms includes tree-, regression- and kernel-based methods, which we selected for their ease of interpretation for the clinician. We also included two novel explainable methods in the comparison. No significant differences in accuracy were observed when comparing the methods, but an improvement was observed when using gene expression instead of mutational status as input for these methods. We concentrated on the current intriguing challenge: model comprehension and ease of use. Our comparison suggests that the tree-based methods are the most interpretable of those tested.

Optimization of Targeted Plant Proteomics Using Liquid Chromatography with Tandem Mass Spectrometry (LC-MS/MS)

This study was conducted to optimize a targeted plant proteomics approach from signature peptide selection and liquid chromatography with tandem mass spectrometry (LC-MS/MS) analytical method development and optimization to sample preparation method optimization. Three typical protein extraction and precipitation methods, including trichloroacetic acid (TCA)/acetone method, phenol method, and TCA/acetone/phenol method, and two digestion methods, including trypsin digestion and LysC/trypsin digestion, were evaluated for selected proteins related to the impact of engineered nanomaterials (ENMs) on wheat (Triticum aestivum) plant growth. In addition, we compared two plant tissue homogenization methods: grinding freeze-dried tissue and fresh tissue into a fine powder using a mortar and pestle aided with liquid nitrogen. Wheat plants were grown under a 16 h photoperiod (light intensity 150 μmol·m^-2·s^-1) for 4 weeks at 22 °C with a relative humidity of 60% and were watered daily to maintain a 70-90% water content in the soil. Processed samples were analyzed with an optimized LC-MS/MS method. The concentration of selected signature peptides for the wheat proteins of interest indicated that the phenol extraction method using fresh plant tissue, coupled with trypsin digestion, was the best sample preparation method for the targeted proteomics study. Overall, the optimized approach yielded the highest total peptide concentration (68,831 ng/g, 2.4 times the lowest concentration) as well as higher signature peptide concentrations for most peptides (19 out of 28). In addition, three of the signature peptides could only be detected using the optimized approach. This study provides a workflow for optimizing targeted proteomics studies.

Selecting 16S rRNA Primers for Microbiome Analysis in a Host-Microbe System: The Case of the Jellyfish Rhopilema nomadica

Amplicon sequencing of the 16S rRNA gene is extensively used to characterize bacterial communities, including those living in association with eukaryotic hosts. Deciding which region of the 16S rRNA gene to analyze and selecting the appropriate PCR primers remains a major decision when initiating any new microbiome study. Based on a detailed literature survey of studies focusing on cnidarian microbiomes, we compared three commonly used primers targeting different hypervariable regions of the 16S rRNA gene, V1V2, V3V4, and V4V5, using the jellyfish Rhopilema nomadica as a model. Although all primers exhibit a similar pattern in bacterial community composition, the performance of the V3V4 primer set was superior to V1V2 and V4V5. The V1V2 primers misclassified bacteria from the Bacilli class and exhibited low classification resolution for Rickettsiales, which represent the second most abundant 16S rRNA gene sequence in all the primers. The V4V5 primer set detected almost the same community composition as the V3V4, but the ability of these primers to also amplify the eukaryotic 18S rRNA gene may hinder bacterial community observations. However, after overcoming the challenges possessed by each one of those primers, we found that all three of them show very similar bacterial community dynamics and compositions. Nevertheless, based on our results, we propose that the V3V4 primer set is potentially the most suitable for studying jellyfish-associated bacterial communities. Our results suggest that, at least for jellyfish samples, it may be feasible to directly compare microbial community estimates from different studies, each using different primers but otherwise similar experimental protocols. More generally, we recommend specifically testing different primers for each new organism or system as a prelude to large-scale 16S rRNA gene amplicon analyses, especially of previously unstudied host-microbe associations.

Rapid detection of serum free light chains by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Introduction: Serum free light chain (FLC) measurements are increasingly prominent for patients with plasma cell disorders (PCDs) in screening, prognostic stratification, and monitoring therapy responses. Objectives: We aimed to develop a sensitive, reliable, and accurate method for diagnosing PCDs that can notably decrease the time and cost of current methods. Methods: Here, we present a novel approach for FLC measurement using immunoenrichment on micro-affinity chromatography in combination with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) detection. In this study, serum free kappa (κ) and free lambda (λ) light chain (LC) levels in the serum of 105 patients were compared between the nephelometric serum FLC quantification and MALDI-TOF MS detection. Results: Cohen's kappa coefficient between the MALDI-TOF MS-based method and the FLC assay revealed an almost perfect agreement in the case of normal (negative) results (κ = 0.92; 95% confidence interval (CI): 0.837 to 0.968) and a good agreement in the case of increased (positive) results (κ = 0.76; 95% CI: 0.608 to 0.870). In Spearman's correlation analysis, the best correlation was found between serum free κ/λ ratios (r = 0.628, 0.496 to 0.732; p <0.0001). Our method showed sensitivity (92.5%) and specificity (76.3%) for discrimination between the κ/λ FLC ratio compared to the serum FLC assay. Conclusion: The proposed method can significantly contribute to diagnosing and monitoring PCDs as it can significantly be time-saving, cost-effective in FLC measurement.

Immunological monitoring after allogeneic stem cell transplantation: T-SPOT.CMV and QuantiFERON-CMV, are they the same?

BACKGROUND

CMV-reactivation and -disease is still a major concern after allogeneic stem cell transplantation [allo-HSCT], despite prophylactic and pre-emptive strategies. In recent years, immunologic monitoring using CMV-IGRA has gained interest to better risk stratify immunocompromised patients or to guide prophylactic therapies. CMV-IGRA can quantify CMV cell-mediated immunity by measuring the interferon-gamma that is released by CD4+ and CD8+ T-lymphocytes in the presence of CMV-antigens. However, the two most widely used CMV-IGRAs, T-SPOT.CMV and QuantiFERON-CMV, have not yet been compared in the setting of an allo-HSCT.

OBJECTIVE

To perform a method comparison between the T-SPOT.CMV and QuantiFERON-CMV 28 and 100 days after allo-HSCT, and to assess predictive values of both tests for CMV-reactivation.

STUDY DESIGN

In a bicentric prospective trial, 27 patients were included. Samples were taken on day +28 and day +100 after allo-HSCT. Patients' clinical information was collected up to 270 days after the transplant. Method comparison was performed using Cohen's kappa.

RESULTS

On day +28 (n=26) after allo-HSCT T-SPOT.CMV gave three positive test results, and QuantiFERON-CMV only two. On day +100 (n=24) T-SPOT.CMV gave seven positive test results, and QuantiFERON-CMV nine. One discordant result was obtained at day +28 (n=26), while six results were discordant at day +100 (n=24). Method comparison showed a strong agreement on day +28 (κ = 0.780 [95% CI: 0.366-1.000]), but only a moderate agreement on day +100 (κ = 0.442 [95% CI: 0.070-0.814]) and on pooled data from both time points (κ = 0.578 [95% CI: 0.300-0.856]). Four clinically significant CMV infections, (CS-CMVi) were observed, all occurring after discontinuation of letermovir-prophylaxis. None of those four patients had a positive result with either test at day +100 (or day +28). Negative predictive values (NPV) and sensitivity are therefore very high at 100% (for both tests, for NPV and sensitivity, measured at day +100). At day+100, positive predictive values (PPV) and specificity were considerably lower (T-SPOT.CMV: PPV 23.5% and specificity 35% - QuantiFERON-CMV: PPV 26.7% and specificity 45%).

CONCLUSION

T-SPOT.CMV and QuantiFERON-CMV only have a moderate agreement (at day +100) after allo-HSCT. Although these IGRAs are very promising, as shown by their very high negative predictive values for protection against CS-CMVi, they are not interchangeable. Future research should stipulate which IGRA was used, and future guidelines should preferably be assay-specific. As the QuantiFERON-CMV to date still lacks a large validation study after allo-HSCT, the moderate agreement with the T-SPOT.CMV poses a significant hurdle in the routine implementation of this test.

Comparison of Creatinine, Urea, Ionized Calcium, and Bicarbonate Methods by 2 POC Systems and a Mainframe Chemistry Analyzer

BACKGROUND

The i-STAT (iST) and GEM Premier ChemSTAT (ChmST) are point-of-care systems that measure electrolytes, metabolites, acid-base parameters, and hematocrit on blood. We compared results for creatinine, urea (blood urea nitrogen [BUN]), total carbon dioxide (tCo2), and ionized calcium (ion Ca) on blood by the ChmST and iST to Beckman DxC600 (DxC600) results for creatinine and urea on plasma and GEM Premier 5000 (GEM5K) results for ion Ca and tCo2 on blood.

METHODS

107 heparinized blood specimens were analyzed on the ChmST and iST systems, with plasma tested by DxC600 for creatinine and BUN and blood tested by GEM5K for ion Ca and tCo2. We evaluated the methods primarily by the mean and SD of the biases at clinically relevant concentrations.

RESULTS

The correlations of ChmST and iST results on blood for creatinine, BUN, ion Ca, and tCo2 correlated to plasma by the DxC600 and to blood by the GEM5K were r ≥ 0.98 for all analytes except for ion Ca on the iST (r = 0.93). The mean and SD of biases were within clinically and analytically acceptable limits for all methods except for tCo2 on the ChmST, which measures bicarbonate with a bicarbonate-sensing electrode. Also, creatinine and BUN by the ChmST were less affected by icterus or hemolysis than were the DxC600 (icterus) and the iST (hemolysis).

CONCLUSIONS

The ChmST and iST results on blood demonstrated strong correlations with each other and with the DxC600 results on plasma. We conclude the ChmST provides reliable results for whole blood creatinine, urea, ion Ca, and tCo2.

Analytical Performance Evaluation of the New GEM(®) Premier™ 5000 in Comparison to the Epoc(®) Blood Gas Analyzer in Horses

Different blood gas analyzers are used in equine practice. Every machine needs to be validated, as they have not been designed for use in horses. The aim of this study was to compare the newly marketed GEM5000 machine to the formerly validated epoc machine for blood gas analysis in horses. In this prospective, non-blinded, comparative laboratory analyzer study, 43 equine blood samples were analyzed on both analyzers and values were compared between the two machines via Lin's concordance analysis, Passing-Bablok regression analysis and Bland-Altman plots. Duplicate measurements were conducted on the GEM5000 machine to evaluate precision. The GEM5000 failed to achieve the required precision for tHb, Hct and iCa²⁺, but achieved acceptable precision for all other parameters. Concordance correlation analysis revealed poor correlation for Na⁺, Cl^-, iCa²⁺, K⁺, Hct and tHb, while there was an at least moderate agreement for all other parameters. Passing-Bablok regression revealed significant constant bias for pCO₂, pO₂, Cl^-, and iCa²⁺ and significant proportional bias for pCO₂, iCa²⁺ and SO₂. Bland-Altman analysis revealed significant systematic bias for Na⁺, Cl^-, iCa²⁺, K⁺, Hct, tHb and SO₂. This study shows that while precision of the GEM5000 is good, values should not be used interchangeably with data obtained from other blood gas analyzers.

Within-Person and Between-Sensor Variability in Continuous Glucose Monitoring Metrics

BACKGROUND

The within-person and between-sensor variability of metrics from different interstitial continuous glucose monitoring (CGM) sensors in adults with type 2 diabetes not taking insulin is unclear.

METHODS

Secondary analysis of data from 172 participants from the Hyperglycemic Profiles in Obstructive Sleep Apnea randomized clinical trial. Participants simultaneously wore Dexcom G4 and Abbott Libre Pro CGM sensors for up to 2 weeks at baseline and again at the 3-month follow-up visit.

RESULTS

At baseline (up to 2 weeks of CGM), mean glucose for both the Abbott and Dexcom sensors was approximately 150 mg/dL (8.3 mmol/L) and time in range (70180 mg/dL [3.910.0 mmol/L]) was just below 80. When comparing the same sensor at 2 different time points (two 2-week periods, 3 months apart), the within-person coefficient of variation (CVw) in mean glucose was 17.4 (Abbott) and 14.2 (Dexcom). CVw for percent time in range: 20.1 (Abbott) and 18.6 (Dexcom). At baseline, the Pearson correlation of mean glucose from the 2 sensors worn simultaneously was r 0.86, root mean squared error (RMSE), 13 mg/dL (0.7 mmol/L); for time in range, r 0.88, RMSE, 8 percentage points.

CONCLUSIONS

Substantial variation was observed within sensors over time and across 2 different sensors worn simultaneously on the same individuals. Clinicians should be aware of this variability when using CGM technology to make clinical decisions.ClinicalTrials.gov Identifier: NCT02454153.

Report from the HarmoSter study: inter-laboratory comparison of LC-MS/MS measurements of corticosterone, 11-deoxycortisol and cortisone

OBJECTIVES

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) panels that include glucocorticoid-related steroids are increasingly used to characterize and diagnose adrenal cortical diseases. Limited information is currently available about reproducibility of these measurements among laboratories. The aim of the study was to compare LC-MS/MS measurements of corticosterone, 11-deoxycortisol and cortisone at eight European centers and assess the performance after unification of calibration.

METHODS

Seventy-eight patient samples and commercial calibrators were measured twice by laboratory-specific procedures. Results were obtained according to in-house and external calibration. We evaluated intra-laboratory and inter-laboratory imprecision, regression and agreement against performance specifications derived from 11-deoxycortisol biological variation.

RESULTS

Intra-laboratory CVs ranged between 3.3 and 7.7%, 3.3 and 11.8% and 2.7 and 12.8% for corticosterone, 11-deoxycortisol and cortisone, with 1, 4 and 3 laboratories often exceeding the maximum allowable imprecision (MAI), respectively. Median inter-laboratory CVs were 10.0, 10.7 and 6.2%, with 38.5, 50.7 and 2.6% cases exceeding the MAI for corticosterone, 11-deoxycortisol and cortisone, respectively. Median laboratory bias vs. all laboratory-medians ranged from -5.6 to 12.3% for corticosterone, -14.6 to 12.4% for 11-deoxycortisol and -4.0 to 6.5% for cortisone, with few cases exceeding the total allowable error. Modest deviations were found in regression equations among most laboratories. External calibration did not improve 11-deoxycortisol and worsened corticosterone and cortisone inter-laboratory comparability.

CONCLUSIONS

Method imprecision was variable. Inter-laboratory performance was reasonably good. However, cases with imprecision and total error above the acceptable limits were apparent for corticosterone and 11-deoxycortisol. Variability did not depend on calibration but apparently on imprecision, accuracy and specificity of individual methods. Tools for improving selectivity and accuracy are required to improve harmonization.

Use of clinical tolerance limits for assessing agreement

In this study, we have further extended the methodology proposed, first, by Lin et al. (2002) and, later, extended by Stevens et al. (2017, 2018), on the coverage probability/probability of agreement, by relaxing the strong parametric assumptions regarding the distribution of the latent trait and developing inference methods allowing to compute both pointwise and simultaneous confidence bands. The methodology requires repeated measurements by at least one of the two measurement methods and accommodates heteroscedastic measurement errors. It performs often very well even when one has only one measurement by one of the two measurement methods and at least five repeated measurements from the other. It circumvents some of the deficiencies of the Bland & Altman limits of agreement method and provides a more direct assessment of the agreement level.

Tracing plant source water dynamics during drought by continuous transpiration measurements: An in-situ stable isotope approach

The isotopic composition of xylem water (δ_X ) is of considerable interest for plant source water studies. In-situ monitored isotopic composition of transpired water (δ_T ) could provide a nondestructive proxy for δ_X -values. Using flow-through leaf chambers, we monitored 2-hourly δ_T -dynamics in two tropical plant species, one canopy-forming tree and one understory herbaceous species. In an enclosed rainforest (Biosphere 2), we observed δ_T -dynamics in response to an experimental severe drought, followed by a ² H deep-water pulse applied belowground before starting regular rain. We also sampled branches to obtain δ_X -values from cryogenic vacuum extraction (CVE). Daily flux-weighted δ¹⁸ O_T -values were a good proxy for δ¹⁸ O_X -values under well-watered and drought conditions that matched the rainforest's water source. Transpiration-derived δ¹⁸ O_X -values were mostly lower than CVE-derived values. Transpiration-derived δ² H_X -values were relatively high compared to source water and consistently higher than CVE-derived values during drought. Tracing the ² H deep-water pulse in real-time showed distinct water uptake and transport responses: a fast and strong contribution of deep water to canopy tree transpiration contrasting with a slow and limited contribution to understory species transpiration. Thus, the in-situ transpiration method is a promising tool to capture rapid dynamics in plant water uptake and use by both woody and nonwoody species.

Beyond the method change in clinical practice: evaluation of insulin-like growth factor I assay

Objectives

Insulin-like growth factor I (IGF-I) is the preferred biomarker for diagnosing and monitoring growth-related disorders but its serum quantification presents several difficulties since different IGF-I assays still leads to different IGF-I concentrations, especially when results are either above or below the normal range.

Methods

We conducted a prospective study between November and December 2020 at a tertiary University Hospital with 212 serum samples to determine the analytical performance of the IGF-I assay on the Cobas e411 (Roche Diagnostics) and compare it with that of the Immulite 2000XPi (Siemens).

Results

In this work, we report for the first time the existence of discrepancies between IGF-I levels measured by Immulite 2000XPi and Cobas e411. Deming regression model provided a slope of 1.570 (95% CI: 1.395-1.745) and an intercept of -58.591 (95% CI: -89.151 to -28.030), with R²=0.967 and average bias of +53.061 with overestimation of IGF-I. It was found that Cobas e411 provides abnormally high IGF-I concentrations, but further studies are required to elucidate the cause of the discrepancies.

Conclusions

Our data can alert clinicians and laboratory professionals of this situation and avoid misinterpretation of increased IGF-I levels as a therapeutic failure rather than as a problem associated with this method change.

Assessing Agreement When Agreement Is Hard to Assess-The Agatston Score for Coronary Calcification

Method comparison studies comprised simple scatterplots of paired measurements, a 45-degree line as benchmark, and correlation coefficients up to the advent of Bland-Altman analysis in the 1980s. The Agatston score for coronary calcification is based on computed tomography of the heart, and it originated in 1990. A peculiarity of the Agatston score is the often-observed skewed distribution in screening populations. As the Agatston score has manifested itself in preventive cardiology, it is of interest to investigate how reproducibility of the Agatston score has been established. This review is based on literature findings indexed in MEDLINE/PubMed before 20 November 2021. Out of 503 identified articles, 49 papers were included in this review. Sample sizes were highly variable (10-9761), the main focus comprised intra- and interrater as well as intra- and interscanner variability assessments. Simple analysis tools such as scatterplots and correlation coefficients were successively supplemented by first difference, later Bland-Altman plots; however, only very few publications were capable of deriving Limits of Agreement that fit the observed data visually in a convincing way. Moreover, several attempts have been made in the recent past to improve the analysis and reporting of method comparison studies. These warrant increased attention in the future.

An improved method for analysis of interrupted time series (ITS) data: accounting for patient heterogeneity using weighted analysis

Interrupted time series (ITS) design is commonly used to evaluate the impact of interventions in healthcare settings. Segmented regression (SR) is the most commonly used statistical method and has been shown to be useful in practical applications involving ITS designs. Nevertheless, SR is prone to aggregation bias, which leads to imprecision and loss of power to detect clinically meaningful differences. The objective of this article is to present a weighted SR method, where variability across patients within the healthcare facility and across time points is incorporated through weights. We present the methodological framework, provide optimal weights associated with data at each time point and discuss relevant statistical inference. We conduct extensive simulations to evaluate performance of our method and provide comparative analysis with the traditional SR using established performance criteria such as bias, mean square error and statistical power. Illustrations using real data is also provided. In most simulation scenarios considered, the weighted SR method produced estimators that are uniformly more precise and relatively less biased compared to the traditional SR. The weighted approach also associated with higher statistical power in the scenarios considered. The performance difference is much larger for data with high variability across patients within healthcare facilities. The weighted method proposed here allows us to account for the heterogeneity in the patient population, leading to increased accuracy and power across all scenarios. We recommend researchers to carefully design their studies and determine their sample size by incorporating heterogeneity in the patient population.

Prospective Evaluation of Different Methods for Volumetric Analysis on [18F]FDG PET/CT in Pediatric Hodgkin Lymphoma

Rationale: Therapy response evaluation by 18F-fluorodeoxyglucose PET/CT (FDG PET) has become a powerful tool for the discrimination of responders from non-responders in pediatric Hodgkin lymphoma (HL). Recently, volumetric analyses have been regarded as a valuable tool for disease prognostication and biological characterization in cancer. Given the multitude of methods available for volumetric analysis in HL, the AIEOP Hodgkin Lymphoma Study Group has designed a prospective analysis of the Italian cohort enrolled in the EuroNet-PHL-C2 trial. Methods: Primarily, the study aimed to compare the different segmentation techniques used for volumetric assessment in HL patients at baseline (PET1) and during therapy: early (PET2) and late assessment (PET3). Overall, 50 patients and 150 scans were investigated for the current analysis. A dedicated software was used to semi-automatically delineate contours of the lesions by using different threshold methods. More specifically, four methods were applied: (1) fixed 41% threshold of the maximum standardized uptake value (SUVmax) within the respective lymphoma site (V41%), (2) fixed absolute SUV threshold of 2.5 (V2.5); (3) SUVmax(lesion)/SUVmean liver >1.5 (Vliver); (4) adaptive method (AM). All parameters obtained from the different methods were analyzed with respect to response. Results: Among the different methods investigated, the strongest correlation was observed between AM and Vliver (rho > 0.9; p < 0.001 for SUVmean, MTV and TLG at all scan timing), along with V2.5 and AM or Vliver (rho 0.98, p < 0.001 for TLG at baseline; rho > 0.9; p < 0.001 for SUVmean, MTV and TLG at PET2 and PET3, respectively). To determine the best segmentation method, we applied logistic regression and correlated different results with Deauville scores at late evaluation. Logistic regression demonstrated that MTV (metabolic tumor volume) and TLG (total lesion glycolysis) computation according to V2.5 and Vliver significantly correlated to response to treatment (p = 0.01 and 0.04 for MTV and 0.03 and 0.04 for TLG, respectively). SUVmean also resulted in significant correlation as absolute value or variation. Conclusions: The best correlation for volumetric analysis was documented for AM and Vliver, followed by V2.5. The volumetric analyses obtained from V2.5 and Vliver significantly correlated to response to therapy, proving to be preferred thresholds in our pediatric HL cohort.