Assay Variability Research Articles

Variability of 7K and 11K SomaScan Plasma Proteomics Assays.

SomaScan is an aptamer-based proteomics assay designed for the simultaneous measurement of thousands of human proteins with a broad range of endogenous concentrations. The 7K SomaScan assay has recently been expanded into the new 11K version. Following up on our previous assessment of the 7K assay, here, we expand our work on technical replicates from donors enrolled in the Baltimore Longitudinal Study of Aging. By generating SomaScan data from a second batch of technical replicates in the 7K version as well as additional intra- and interplate replicate measurements in the new 11K version using the same donor samples, this work provides useful precision benchmarks for the SomaScan user community. Beyond updating our previous technical assessment of the 7K assay with increased statistics, here, we estimate interbatch variability, assess inter- and intraplate variability in the new 11K assay, compare the observed variability between the 7K and 11K assays (leveraging the use of overlapping pairs of technical replicates), and explore the potential effects of sample storage time (ranging from 2 to 30 years) in the assays' precision.

Comparison of Four Chimeric Antigens and Commercial Serological Assays for the Diagnosis of Trypanosoma cruzi Infection

Chagas disease (CD), a neglected tropical disease caused by Trypanosoma cruzi, is a significant public health issue particularly in Latin America, affecting millions worldwide. Diagnosis is a challenge owing to the genetic diversity of T. cruzi and the complexities involved in selecting antigens for the detection of anti–T. cruzi antibodies. This study evaluated four chimeric recombinant antigens (IBMP-8.1, IBMP-8.2, IBMP-8.3, and IBMP-8.4) designed to enhance diagnostic accuracy by addressing assay variability. We compared the diagnostic performance of these chimeric antigens using indirect ELISA as a diagnostic platform, with three commercial serological assays in Brazil, analyzing 100 serum samples from individuals with confirmed CD and 86 from non-infected controls. The results revealed that all assays and antigens demonstrated an area under the receiver operating characteristic curve of 100%, signifying their exceptional ability to distinguish between CD-positive and CD-negative samples. Notably, the chimeric antigens achieved 100% sensitivity, specificity, accuracy, and kappa index, equaling or surpassing the commercial assays. This research highlights the efficacy of IBMP chimeric antigens as reliable diagnostic tools for CD, suggesting their potential integration into commercial diagnostic platforms to enhance the accuracy and reliability of CD detection.

Assay variables and early clinical evaluation of low-angle light scattering for platelet function analysis.

The recently developed platelet aggregation technique based on low-angle light scattering (LaSca) in diluted platelet-rich plasma (PRP) requires only a small sample volume and provides information about platelet aggregation and shape change. This study aimed to investigate the influence of preanalytical and analytical variables and to validate the method in a real-life pediatric hematology hospital setting. Platelet aggregation was induced by ADP in diluted PRP in the presence of 2mM calcium at 23°C. The study included healthy adults (n = 30), healthy children (n = 20), and pediatric patients with suspected or diagnosed platelet function abnormalities (n = 25). The assay parameters were stable for at least 3h after isolation of PRP and were sensitive to plasma dilution in the range of 2-8%. The initial aggregation velocity was significantly reduced in pediatric patients compared with healthy children (p < 0.05). ADP-induced light transmission amplitude was moderately correlated with LaSca amplitude of aggregation in healthy children (p = 0.52, p < 0.05) but not in pediatric patients. We standardized the protocol for platelet aggregation assessment by LaSca and characterized the influence of preanalytical and analytical variables on it.

12426 Performance Of Dehydroepiandrosterone-Sulphate In Diagnosing Mild Autonomous Cortisol Secretion: A Systematic Review And Meta-Analysis

Abstract Disclosure: J. Saini: None. B. Salama: None. S.R. Chacko: None. K. Yu: None. I. Bancos: None. Objective: Measurement of baseline dehydroepiandrosterone sulfate (DHEAS) is suggested by the guidelines in support of diagnosing mild autonomous cortisol secretion (MACS). However, evidence on the diagnostic accuracy of DHEAS in MACS is difficult to interpret due to differences in the diagnostic cutoffs, small sample size, and heterogeneous reference standards. We aimed to conduct a systematic review and meta-analysis of published literature to assess the performance of DHEAS in diagnosing MACS, as defined in the 2023 guidelines. Methods: A comprehensive search was conducted using several databases from each database’s inception to January 8th, 2024. Databases include Ovid MEDLINE (R) and Epub Ahead of Print, In-Process &amp; Other Non-Indexed Citations, and Daily, Ovid EMBASE, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Databases of Systematic Reviews, and Scopus. Only original studies of at least 20 participants were included. MACS was defined as post-dexamethasone cortisol &amp;gt;1.8 mcg/dL. QUADAS-2 was used to assess the risk of bias. Bivariate and random effects meta-analysis was used to generate pooled diagnostic accuracy estimates. Results: The initial search yielded 285 articles, and only 7 studies met the inclusion criteria. In 7 studies (1 from North America, 3 from Asia, and 3 from Europe), a total of 574 patients with MACS and 830 referent subjects (patients with adrenal tumors without MACS) were included. The mean age was specified only in 5 studies and was similar in patients with MACS (55.5 years) and referent group (53.3 years). Patients with MACS had a higher number of women (323/472, 68.4%) as compared to the referent group (352/658, 53.4%). DHEAS cutoffs studied included: lower cutoff of age-and sex-specific ranges (3 studies), 40 mcg/dL (3 studies), 60 mcg/dL (1 study), and 67.5 mcg/dL (1 study). With increasing DHEAS cutoff, sensitivity for MACS diagnosis increased, and specificity decreased. Most studies (4 studies) used the chemiluminescent immunoassay to measure DHEAS. A meta-analysis of studies using DHEAS cut-off between 40-70 mcg/dL was performed, with a pooled sensitivity of 68% (95% CI: 51-81) and a pooled specificity of 85% (78-89). The positive likelihood ratio was 4 (95% CI: 3-6; I2=36.94, P=0.175) and the negative likelihood ratio was 0.4 (0.3-0.6; I2=49.97, P=0.092). Most studies were at a high risk of bias for selection of patients, index, or reference standard. Conclusion: Based on limited heterogeneous evidence, measurement of DHEAS provides additional value in diagnosing MACS. Further larger diagnostic accuracy studies should explore various DHEAS cutoffs and consider assay variability. Presentation: 6/3/2024

7560 Using a Single Pre-test Cortisol Level To Reduce The Need For Dynamic Testing For Adrenal Insufficiency In A Southeast Asian Population

Abstract Disclosure: V. Ramadoss: None. L. Tan: None. A.E. Teo: None. K. Lazarus: None. K. Meeran: None. D. Deepak: None. L. Ong: None. C. Khoo: None. P. Eng: None. Introduction: The Short Synacthen Test (SST) is widely used in clinical practice to assess Adrenal Insufficiency (AI). Despite its relative ease of administration, Synacthen use is limited by its availability and its administration demands supervision by experienced staff, resulting in increased testing cost. A single measurement of serum cortisol has been shown to predict AI, but the suggested threshold varies according to the patient cohort studied, assay variation and the prevalence of the condition relative to the size of population tested. This study aims to (a) identify a threshold cortisol level to screen for AI in a South-East Asian population and (b) to determine the utility of a stimulated 60-minute cortisol level in the diagnosis of AI. Methods: This is a retrospective analysis of SSTs (250 micrograms) performed in our institution between 28th February 2022 to 28th February 2023. Serum cortisol in our institution was measured by Abbott Alinity analysers. We defined a normal response as a stimulated cortisol value of ≥ 420nmol/L at either 30-minutes, 60-minutes, or at both time points. Logistic regression analysis was performed to predict normal responses based on baseline cortisol level. Results: Median cortisol level at baseline, 30-minutes, and 60-minutes after Synacthen stimulation were 254 (IQR 191-320) nmol/L, 499 (IQR 415 -585) nmol/L, 574 (IQR 476 -662) nmol/L respectively. A total of 785 SSTs were performed, out of which 83.1% were normal and 16.9% were abnormal. Of the 785 SSTs, 55 (7.0%) would have failed if only the 30-minute cortisol was assessed without the 60-minute value, whereas 10 (1.4%) would have failed if only the 60-minute cortisol was assessed without the 30-minutes value. An early morning basal cortisol (0800am to 1200pm) cut-off of &amp;lt;300nmol/L identified subnormal cortisol with 95.0% sensitivity and an afternoon cortisol (1200pm to 1700) of &amp;lt; 312nmol/L achieved 95.2% sensitivity. A basal cortisol level of &amp;lt; 100nmol/L will confirm AI with 97.3% specificity. Using a basal cortisol level of ≥ 300nmol/L, 94.8% of individuals go on to pass the SST. Use of this basal cortisol value would avoid 252 (32.1%) SSTs. Conclusion: A single measurement of basal cortisol of ≥ 300nmol/L has the potential to exclude AI with 95% sensitivity on Abbott Alinity platform in our cohort of patients. Using a threshold cortisol level of 300nmol/L, at least 32% of the SSTs could be avoided. This would have improved patients experience with cost savings implications. Furthermore, a stimulated 60-minute cortisol level identifies 55 (7%) of individuals who would otherwise be misclassified as AI, thereby avoiding unnecessary long-term glucocorticoid replacement. Presentation: 6/1/2024

8008 Insulin-like Growth Factor-1 (IGF-1) Level Fluctuations and Patient Reported Outcomes (PROMS) During Treatment with Long-acting Somatostatin Receptor Ligands (SRLs) for Acromegaly: a Prospective Study

Abstract Disclosure: I. Remba-Shapiro: None. J.R. Schweizer: None. K.J. Liebert: Consulting Fee; Self; Crinetics, Recordati Rare Diseases, Novo Nordisk. K. Schilbach: None. M. Adams: Consulting Fee; Self; Chiesi. N.A. Tritos: None. M. Bidlingmaier: Consulting Fee; Self; Ipsen, Ionis Pharmaceuticals Inc., Novartis Pharmaceuticals, Novo Nordisk, Pfizer, Inc., Roche Pharmaceuticals. L.B. Nachtigall: Consulting Fee; Self; Crinetics. Grant Recipient; Self; Amryt, Recordati Rare Diseases. Background: SRLs are the most used medical therapy for acromegaly. Some patients report symptoms of acromegaly towards the end of the injection cycle even when IGF-1 levels are controlled. IGF-1 fluctuations within an injection cycle have been observed. In this study we investigated the variability of biochemical markers and PROMS in patients receiving long-acting SRLs. Methods: Subjects with acromegaly controlled with monthly lanreotide depot or octreotide LAR were recruited. Blood samples at 1 and 4 weeks after SLR injection were collected in 2 consecutive cycles. Clinical characteristics were evaluated. Quality of life (QoL) surveys included: Acromegaly Quality of Life Questionnaire (AcroQoL) (higher scores = better QoL) and Patient Assessed Acromegaly Symptom Questionnaire (PASQ) (higher scores = worse QoL). Week 1 vs. week 4 values were compared. Quest Diagnostics LC-MS assay was used to measure IGF-1. Coefficient of variation (CV = (IGF-1 SD)/(IGF-1 mean)%) of IGF-1 was calculated. Values ≤5% were interpreted as being a consequence of assay variability. Variables are presented as mean (SD) and compared using t-test; p &amp;lt;0.05 was considered significant. Results: Patients (6 women, 4 men) had a mean age of 56.1 (15.4) years. Eight underwent TSS. One had diabetes mellitus, 3 had hypertension. Mean IGF-1 index (IGF-1 x upper limit of normal) at screening was 0.63 (0.23). BMI was 27.7 (5.8) kg/m2. IGF-1 index at week 1 was 0.57 [0.16] vs. 0.61 [0.23] at week 4, p=0.271. Insulin levels were lower in week 1 vs. week 4 (7.3 [4.4] vs. 9.7 [6.0]mIU/mL p=0.041). There were no significant differences in GH, glucose, weight, blood pressure and ring size in week 1 vs. week 4. PASQ varied significantly within the injection cycle with higher scores in week 4 (18.1 [10.8]) compared to week 2 (16.1 [10.4] p=0.032) and week 3 (14.2 [8.8] p= 0.002). ACROQoL scores did not differ by injection phase. IGF-1 increased more than assay CV from week 1 to week 4 in 8/20 (40%) determinations. An ROC curve identified an IGF-1 index cutoff of 0.57 at week 4 (AUC: 0.812, p=0.021) as a predictor of IGF-1 index increase within the injection cycle (CV &amp;gt; 5%): sensitivity 88%, specificity 75%. Five patients had IGF-1 index &amp;gt; 0.57 at week 4 during both cycles (range 0.60-1.2). In this group, mean IGF-1 index was higher at week 4 vs. week 1 (0.77 [0.21] vs. 0.66 [0.14] p=0.026). The 5 patients with IGF-1 index &amp;lt; 0.57 at week 4 had no difference in IGF-1 index between week 4 and week 1 (0.48 [0.14] vs. 0.44 [0.09] p=0.144). Conclusions: This prospective study of patients with acromegaly controlled with long-acting SRLs demonstrates injection phase variability in self-reported symptoms by PASQ. An IGF-1 index &amp;gt; 0.57 at the end of the cycle may warrant injection phase-dependent monitoring. Larger studies to confirm the IGF-1 cutoff above which patients should be monitored in a cycle-dependent manner will allow an individualized approach to optimize management. Presentation: 6/2/2024

A-038 Interlaboratory Comparison of Parathyroid Hormone Analytical Results Across Clinical Assays from 8 Manufacturers - Steps Towards Standardization

Abstract Background Parathyroid hormone (PTH) is an 84 amino acid peptide produced by the parathyroid gland and is a key biomarker used for the diagnosis and treatment of Chronic Kidney Disease-Mineral and Bone Disorder, as well as hypo- and hyperparathyroidism. PTH clinical assays were previously reported to exhibit significant inter-assay measurement variability, which limits the utility of PTH as a diagnostic biomarker and can result in the misclassification of patients. Thus, there is a need for PTH clinical assay standardization to improve clinical assay measurement agreement. The Centers for Disease Control and Prevention’s Clinical Standardization Program (CDC-CSP) will launch a PTH standardization program, which is in support of and coordinated with the IFCC Committee on Bone Metabolism. In preparation, the CDC-CSP conducted an Inter-Laboratory Comparison Study to evaluate the current status of PTH inter-assay variability and to investigate potential sources of variability. Methods Eight PTH assay manufacturer’s laboratories measured PTH in 42 deidentified, fresh-frozen single donor serum samples in duplicate over 2 independent runs. Sample PTH concentrations ranged from 1.3 - 324 pg/mL, based on initial screening values. Five manufacturers submitted data for 2 different assays, resulting in PTH measurements from 13 assays total. Data were submitted to the CDC CSP for analysis. Results Assay precision was &amp;lt;5% for 10/13 measurement procedures (MP) assessed and 3 MPs exhibited precisions between 5 - 18%. Assay-specific PTH measurements demonstrated good linear correlation compared to the all-assay mean concentration. Interestingly, inter-assay variability increased with increasing PTH concentrations, with individual sample standard deviations increasing from 2.9 - 123, with a mean SD of 24.1 and individual sample CVs increasing from 18.9 - 44.5%, with a mean CV of 24.2%. Conclusions This study provides new insights into PTH inter-assay variability and assay performance for assays commonly used in the clinical setting. The findings of this PTH Interlaboratory Comparison Study establish a baseline for PTH inter-assay variability and will guide future PTH standardization efforts.

Interpretation of TSH results can be improved by reference values fluctuating in time.

The secretion of thyroid stimulating hormone (thyrotropin, TSH), is characterized by a marked circadian rhythm. Plasma or serum TSH values are significantly lower in the afternoon and in the evening as compared to the early morning. As in clinical practice, blood sampling time shows an important variation, a reliable assessment of thyroid status is often not an easy task for the clinician. The biological variation of TSH plays a major role in the intra-individual variability of TSH results in serum or plasma. The observed intra-day variation largely exceeds the reported inter-vendor variation and the coefficient of variation of clinical TSH assays. Therefore, a mathematical solution was sought for correcting interpretation of TSH results for sampling time. We have developed a cosinor model which allows to compensate TSH decision values for the fluctuating serum or plasma TSH concentrations throughout the day. The following mathematical function could be derived: corrected TSH cutoff_value (mIU/L)=0.40+0.24*cos(((π/12) *T)+6) in which T represents the time (hours). This mathematical function can be easily implemented into a laboratory's informatics system and furthermore allows a better tailored diagnosis of (subclinical) hyperthyroidism, regardless the blood sampling time. Implementing the corrected cut-off values result in a marked reduction of apparent (false positive) hyperthyroidism diagnosis, in particular in the afternoon.

Transmission-blocking activities of artesunate, chloroquine, and methylene blue on Plasmodium vivax gametocytes.

Plasmodium vivax is now the main cause of malaria outside Africa. The gametocytocidal effects of antimalarial drugs are important to reduce malaria transmissibility, particularly in low-transmission settings, but they are not well characterized for P. vivax. The transmission-blocking effects of chloroquine, artesunate, and methylene blue on P. vivax gametocytes were assessed. Blood specimens were collected from patients presenting with vivax malaria, incubated with or without the tested drugs, and then fed to mosquitos from a laboratory-adapted colony of Anopheles dirus (a major malaria vector in Southeast Asia). The effects on oocyst and sporozoite development were analyzed under a multi-level Bayesian model accounting for assay variability and the heterogeneity of mosquito Plasmodium infection. Artesunate and methylene blue, but not chloroquine, exhibited potent transmission-blocking effects. Gametocyte exposures to artesunate and methylene blue reduced the mean oocyst count 469-fold (95% CI: 345 to 650) and 1,438-fold (95% CI: 970 to 2,064), respectively. The corresponding estimates for the sporozoite stage were a 148-fold reduction (95% CI: 61 to 470) and a 536-fold reduction (95% CI: 246 to 1,311) in the mean counts, respectively. In contrast, high chloroquine exposures reduced the mean oocyst count only 1.40-fold (95% CI: 1.20 to 1.64) and the mean sporozoite count 1.34-fold (95% CI: 1.12 to 1.66). This suggests that patients with vivax malaria often remain infectious to anopheline mosquitos after treatment with chloroquine. Use of artemisinin combination therapies or immediate initiation of primaquine radical cure should reduce the transmissibility of P. vivax infections.

Performance of three multiplex real-time PCR assays for simultaneous detection of 12 infectious pathogens in mice affected with respiratory and digestive diseases.

Research quality can be improved with reliable and reproducible experimental results when animal experiments are conducted using laboratory animals with guaranteed microbiological and genetic quality through health monitoring. Therefore, health monitoring requires the rapid and accurate diagnosis of infectious diseases in laboratory animals. This study presents a performance evaluation of a commercially available multiplex real-time PCR (mRT-PCR) assay for the rapid detection of 12 infectious pathogens (Set 1: Sendai virus [SeV, formally murine respirovirus], Mycoplasma spp., Rodentibacter pneumotropicus, and Rodentibacter heylii; Set 2: Helicobacter spp., Murine norovirus [MNV], Murine hepatitis virus [MHV], and Salmonella spp.; Set 3: Staphylococcus aureus, Streptobacillus moniliformis, Corynebacterium kutscheri, and Pseudomonas aeruginosa). To evaluate the efficacy of the mRT-PCR assay, 102 clinical samples encompassing fecal and cecal specimens were analyzed. The resulting data were then compared with the findings from sequence analysis for validation. The assay's detection limit ranged from 1 to 100 copies per reaction. Specificity testing involving various viruses and bacteria indicated no cross-reactivity between strains. Additionally, the assay exhibited good reproducibility, with mean coefficients of variation for inter- and intra assay variation below 3%. The overall positive rate was 52.9% (n = 54), with the mRT-PCR assay findings matching sequence analysis results (κ = 1). MHV (n = 29, 28.4%) was the most prevalent pathogen, followed by Helicobacter spp. (n = 28, 27.5%), R. heylii (n = 18, 17.6%), Mycoplasma spp. (n = 14, 13.7%), MNV (n = 12, 11.8%), S. aureus (n = 9, 8.8%), P. aeruginosa (n = 4, 3.9%), and R. pneumotropicus (n = 1, 0.9%). This assay offers a rapid turnaround time of 100 min, including 30 min for DNA preparation and 70 min for target DNA/RNA amplification. It ensures accuracy, minimizing false positives or negatives, making it a convenient tool for the simultaneous detection of infectious diseases in many samples. Overall, the propose‑d assay holds promise for the effective detection of the most important pathogens in laboratory animal health monitoring.

Detection of residual pluripotent stem cells in cell therapy products utilizing droplet digital PCR: an international multisite evaluation study.

The presence of residual undifferentiated pluripotent stem cells (PSCs) in PSC-derived cell therapy products (CTPs) is a major safety issue for their clinical application, due to the potential risk of PSC-derived tumor formation. An international multidisciplinary multisite study to evaluate a droplet digital PCR (ddPCR) approach to detect residual undifferentiated PSCs in PSC-derived CTPs was conducted as part of the Health and Environmental Sciences Institute Cell Therapy-TRAcking, Circulation & Safety Technical Committee. To evaluate the use of ddPCR in quantifying residual iPSCs in a cell sample, different quantities of induced pluripotent stem cells (iPSCs) were spiked into a background of iPSC-derived cardiomyocytes (CMs) to mimic different concentrations of residual iPSCs. A one step reverse transcription ddPCR (RT-ddPCR) was performed to measure mRNA levels of several iPSC-specific markers and to evaluate the assay performance (precision, sensitivity, and specificity) between and within laboratories. The RT-ddPCR assay variability was initially assessed by measuring the same RNA samples across all participating facilities. Subsequently, each facility independently conducted the entire process, incorporating the spiking step, to discern the parameters influencing potential variability. Our results show that a RT-ddPCR assay targeting ESRG, LINC00678, and LIN28A genes offers a highly sensitive and robust detection of impurities of iPSC-derived CMs and that the main contribution to variability between laboratories is the iPSC-spiking procedure, and not the RT-ddPCR. The RT-ddPCR assay would be generally applicable for tumorigenicity evaluation of PSC-derived CTPs with appropriate marker genes suitable for each CTP.

Improving the Accuracy of Permeability Data to Gain Predictive Power: Assessing Sources of Variability in Assays Using Cell Monolayers.

The ability to predict the rate of permeation of new compounds across biological membranes is of high importance for their success as drugs, as it determines their efficacy, pharmacokinetics, and safety profile. In vitro permeability assays using Caco-2 monolayers are commonly employed to assess permeability across the intestinal epithelium, with an extensive number of apparent permeability coefficient (Papp) values available in the literature and a significant fraction collected in databases. The compilation of these Papp values for large datasets allows for the application of artificial intelligence tools for establishing quantitative structure-permeability relationships (QSPRs) to predict the permeability of new compounds from their structural properties. One of the main challenges that hinders the development of accurate predictions is the existence of multiple Papp values for the same compound, mostly caused by differences in the experimental protocols employed. This review addresses the magnitude of the variability within and between laboratories to interpret its impact on QSPR modelling, systematically and quantitatively assessing the most common sources of variability. This review emphasizes the importance of compiling consistent Papp data and suggests strategies that may be used to obtain such data, contributing to the establishment of robust QSPRs with enhanced predictive power.

Microliter Whole Blood Neutrophil Assay Preserving Physiological Lifespan and Functional Heterogeneity.

For in vitro neutrophil functional assays, neutrophils are typically isolated from whole blood, having the target cells exposed to an artificial microenvironment with altered kinetics. Isolated neutrophils exhibit limited lifespans of only a few hours ex vivo, significantly shorter than the 3-5 day lifespan of neutrophils in vivo. In addition, due to neutrophils' inherently high sensitivity, neutrophils removed from whole blood exhibit stochastic non-specific activation that contributes to assay variability. Here, a method - named "µ-Blood" - is presented that enables functional neutrophil assays using a microliter of unprocessed whole blood. µ-Blood allows multiple phenotypic readouts of neutrophil function (including cell/nucleus morphology, motility, recruitment, and pathogen control). In µ-Blood, neutrophils show sustained migration and limited non-specific activation kinetics (<0.1% non-specific activation) over 3-6 days. In contrast, neutrophils isolated using traditional methods show increased and divergent activation kinetics (10-70% non-specific activation) in only 3h. Finally, µ-Blood allows the capture and quantitative comparison of distinct neutrophil functional heterogeneity between healthy donors and cancer patients in response to microbial stimuli with the preserved physiological lifespan over 6 days.

High variability in assays of blood markers of collagen turnover in cardiovascular disease: Implications for research and clinical practice.

Fibrosis is a common feature of many chronic diseases, including heart failure, which can have deleterious effects on cardiac structure and function that are associated with adverse outcomes. By-products of collagen synthesis and degradation, such as carboxy- and amino-terminal pro- or telo-peptides of collagen type I and III (PICP, PINP, PIIINP, and CITP) have been extensively investigated as markers of fibrosis. Although the majority of studies report on the reproducibility of their assay results, there is no a comparison of biomarker assays across studies. Therefore, we conducted a systematic review adhering to PRISMA guidelines. The search terms employed in Medline were: 'collagen AND cardiac' or 'collagen AND heart'. This query yielded a total of 1049 articles. Thereafter, specific search criteria were applied: (i) original English-language papers; (ii) human studies; (iii) in-vivo investigations; and (iv) blood/serum/plasma samples. Overall, 89 studies were identified (42 on PIIINP, 32 on PICP, 29 on CITP, and 17 on PINP). The range of reported values for PIIINP was between 0.06 to 11 800 μg/l; for PICP 0.006 to 1265 μg/l; for CITP 0.3 to 5450 μg/l; for PINP 0.15 to 80 μg/l. Extreme variations in values for fibrosis biomarkers were observed across studies, especially when different assays were used, but also with the same assays. Our findings show that it is challenging to ascertain normal ranges or compare studies for the measurement of fibrosis biomarkers. Given the potential implications for clinical practice and current lack of awareness of these issues, this subject warrants comprehensive acknowledgement and understanding.

Development of a rapid and fully automated factor VIII inhibitor assay, insensitive to emicizumab, and a lowest level of quantification of 0.2 BU/mL

BackgroundFactor (F)VIII inhibitors are measured using labor- and resource-expensive Nijmegen or Bethesda assays, which lack sensitivity for low-titer inhibitors and show high variations in quality surveys, mainly because of manual assay procedures. ObjectivesThe goal of this study was the development of a fast and fully automated FVIII inhibitor assay by using recombinant (r)FVIII as substrate and dedicated equipment for execution of the test. MethodsA new rapid, fully automated, FVIII inhibitor assay is presented, the core of which is use of full-length recombinant FVIII (rFVIII; Kovaltry, Bayer) as inhibitor substrate instead of plasma FVIII, resulting in rapid binding of inhibitors to rFVIII due to absence of von Willebrand factor. Dramatic shortening of incubation time facilitated full automation on an analyzer capable of 3 subsequent sample dilution steps and 3 reagent additions. Equal volume mixtures of sample and rFVIII (1.0 U/mL) were incubated for 10 minutes at 37 °C, whereafter remaining FVIII activity was analyzed with a kinetic chromogenic assay, allowing inhibitor activity calculation without preceding FVIII activity calibration, using a Ceveron s100 analyzer (Technoclone). ResultsMean titer in 60 nonhemophiliacs was 0.0 BU/mL (SD, 0.1), yielding a limit of blank of 0.1 BU/mL and lower limit of quantification of 0.2 BU/mL. Analyses were performed with the new method and a Nijmegen assay in 28 inhibitor-positive clinical samples, 14 containing emicizumab and 14 without. Correlation coefficient in emicizumab-free type I inhibitor samples was 1.0. Emicizumab dependency of the method was excluded in spiking experiments with inhibitor-positive samples. Reproducibility was tested by analyzing 7 samples in 3 laboratories for 5 days, twice daily; coefficients of variation of all samples were <15%. ConclusionWe present development data of a sensitive and specific rapid, automated FVIII inhibitor assay generating results within 20 minutes that is less resource-intensive than standard assays with potential to improve assay variability.

Blood collection tube and anticoagulant influence on SARS-CoV-2 antibody and avidity levels

SARS-CoV-2 serology plays a crucial role in assessing COVID-19 vaccine immunogenicity and antibody responses to SARS-CoV-2 infection. Tube type and anticoagulant may influence serology results. Thus, understanding the influence of these variables in test results is key.We evaluated the influence of serum collection tube type and anticoagulant on anti-SARS-CoV-2 spike antibody levels detected by enzyme-linked immunosorbent assays (ELISAs) and Luminex multiplex assays (11-plex) in serum and plasma samples. Anti-spike IgG avidity was also evaluated in both sample types.No significant differences were found between serology assay results using different blood (serum) collection tube types. However, significantly lower antibody concentrations (p < 0.05) were observed in tubes with the anticoagulants sodium citrate and acid citrate dextrose (ACD) in the ELISA and Multiplex assays (n = 29), compared to expected concentrations. These differences mostly disappeared after adjusting for the dilution factor caused by the anticoagulant volume, indicating that anticoagulant does not significantly impact the assay results, while anticoagulant volume does.There was a significant difference (p < 0.05) in IgG avidity (M) of plasma samples (p < 0.05) compared to serum, but anticoagulant type had no effect.Overall, these findings indicate that the choice of collection tube may introduce subtle variations in assay results if the volumes of anticoagulants are not taken into consideration. Additionally, differences between serum and anticoagulant-treated plasma matrices were observed in avidity ELISAs, indicating that these samples are not interchangeable for these assays; a finding that requires further investigation.

Evaluation of clopidogrel response in healthy cats using a novel viscoelastic test and thromboelastography.

Cats with cardiomyopathy face an increased risk of arterial thromboembolism (ATE). Although clopidogrel is frequently utilized to mitigate this risk, feline responses to this therapy exhibit variability. This study evaluated 2 viscoelastic devices, thromboelastography (TEG) and Viscoelastic Coagulation Monitor (VCM), for monitoring clopidogrel in cats in comparison to light transmission aggregometry (LTA). Twenty-eight healthy cats received clopidogrel for 7 days. Blood was collected at baseline and after treatment for analysis by TEG, VCM, and LTA. On LTA, maximum amplitude, slope, and area under the curve (AUC) significantly decreased after treatment (p < 0.0001). On VCM, maximum clot firmness (MCF) significantly increased after treatment (p = 0.002). On TEG, R-time significantly prolonged (p = 0.024), while K and alpha angle significantly changed (p = 0.0002 and p = 0.0014, respectively). There was a moderate negative correlation between TEG R-time and LTA AUC (r = -0.39, p = 0.042). Eight cats were identified as non-responders to clopidogrel. Of the 8 non-responders, 6 (75%) had shortened R time after treatment. VCM appeared to be less discriminatory in identifying non-responders. LTA remained the gold standard of monitoring clopidogrel treatment in cats. Unexpected changes on VCM and TEG were likely related to high interindividual and assay variability and increased sensitivity of feline platelets. R-time on TEG may have potential utility for point-of-care monitoring of clopidogrel response in cats.

Field Study and Correlative Studies of Factor IX Variant FIX-R338L in Participants Treated with Fidanacogene Elaparvovec.

Fidanacogene elaparvovec, an adeno-associated virus-based gene therapy vector expressing the high-activity factor IX (FIX) variant FIX-R338L, is in development for hemophilia B. One-stage clotting (OS) assays and chromogenic substrate (CS) assays are commonly used to measure FIX-R338L variant activity. Data from ongoing trials suggest FIX activity varies between different OS and CS assays. To better understand FIX-R338L activity in clinical samples, an international multisite field study was conducted across a central laboratory and 18 local laboratories, using standard protocols, reagents, and instrumentation, with individual participant samples from a phase 1/2a study of fidanacogene elaparvovec. Unlike the wild-type FIX control, FIX-R338L activity was higher with the OS silica-based assay versus OS ellagic acid-based and CS assays. Variation in FIX activity was greater at the lowest activity levels. Activated FIX (FIXa) in plasma could result in higher OS assay activity or increased thrombin generation, which could overestimate FIX activity. However, FIXa was not detected in the participant samples, indicating that it was not contributing to the OS assay differences. Since individuals on gene therapy may receive exogenous replacement FIX products, replacement products were spiked into patient plasma samples to target a therapeutic concentration. Exogenous FIX was additive to endogenous FIX-R338L, with no interference from FIX-R338L. These results demonstrate FIX-R338L activity can be measured with OS and CS assays in clinical laboratories and provide insight into assay variability when measuring FIX with endogenously produced FIX-R338L. The findings may help establish best practices for measuring FIX-R338L activity (Clinicaltrials.gov identifier: NCT02484092).

Sources of variability in Luminex bead-based cytokine assays: Evidence from twelve years of multi-site proficiency testing

Bead array assays, such as those sold by Luminex, BD Biosciences, Sartorius, Abcam and other companies, are a well-established platform for multiplexed quantification of cytokines and other biomarkers in both clinical and discovery research environments. In 2011, the National Institute of Allergy and Infectious Diseases (NIAID)-funded External Quality Assurance Program Oversight Laboratory (EQAPOL) established a proficiency assessment program to monitor participating laboratories performing multiplex cytokine measurements using Luminex bead array technology. During every assessment cycle, each site was sent an assay kit, a protocol, and blinded samples of human sera spiked with recombinant cytokines. Site results were then evaluated for performance relative to peer laboratories. After over a decade of biannual assessments, the cumulative dataset contained over 15,500 bead array observations collected at more than forty laboratories in twelve countries. These data were evaluated alongside post-assessment survey results to empirically test factors that may contribute to variability and accuracy in Luminex bead-based cytokine assays. Bead material, individual technical ability, analyte, analyte concentration, and assay kit vendor were identified as significant contributors to assay performance. In contrast, the bead reader instrument model and the use of automated plate washers were found not to contribute to variability or accuracy, and sample results were found to be highly-consistent between assay kit-manufacturing lots and over time. In addition to these statistical analyses, subjective evaluations identified technical ability, instrument failure, protocol adherence, and data transcription errors as the most common causes of poor performance in the proficiency program. The findings from the EQAPOL multiplex program were then used to develop recommended best practices for bead array monitoring of human cytokines. These included collecting samples to assay as a single batch, centralizing analysis, participating in a quality assurance program, and testing samples using paramagnetic-bead kits from a single manufacturer using a standardized protocol.

Uniform sized cancer spheroids production using hydrogel-based droplet microfluidics: a review.

Three-dimensional (3D) cell culture models have been extensively utilized in various mechanistic studies as well as for drug development studies as superior in vitro platforms than conventional two-dimensional (2D) cell culture models. This is especially the case in cancer biology, where 3D cancer models, such as spheroids or organoids, have been utilized extensively to understand the mechanisms of cancer development. Recently, many sophisticated 3D models such as organ-on-a-chip models are emerging as advanced in vitro models that can more accurately mimic the in vivo tissue functions. Despite such advancements, spheroids are still considered as a powerful 3D cancer model due to the relatively simple structure and compatibility with existing laboratory instruments, and also can provide orders of magnitude higher throughput than complex in vitro models, an extremely important aspects for drug development. However, creating well-defined spheroids remain challenging, both in terms of throughputs in generation as well as reproducibility in size and shape that can make it challenging for drug testing applications. In the past decades, droplet microfluidics utilizing hydrogels have been highlighted due to their potentials. Importantly, core-shell structured gel droplets can avoid spheroid-to-spheroid adhesion that can cause large variations in assays while also enabling long-term cultivation of spheroids with higher uniformity by protecting the core organoid area from external environment while the outer porous gel layer still allows nutrient exchange. Hence, core-shell gel droplet-based spheroid formation can improve the predictivity and reproducibility of drug screening assays. This review paper will focus on droplet microfluidics-based technologies for cancer spheroid production using various gel materials and structures. In addition, we will discuss emerging technologies that have the potential to advance the production of spheroids, prospects of such technologies, and remaining challenges.