Bland-Altman Difference Plots Research Articles

7938 Validation of Inflammatory Cytokine Multiplex Array With Variations in Target Panel

Abstract Disclosure: W.M. Sanders: None. C.A. Karvonen-Gutierrez: None. D.S. McConnell: None. Background: Multiplex arrays are an invaluable tool for conducting large-scale biomarker research as they provide a high-throughput, cost-effective method for quantifying a panel of endocrine markers. However, the shared reaction environment between antibodies of differing reactivities creates the potential for inducing a technical difference in the assay methods due to any variation in panel selection. Methods: We evaluated the R&D Systems Luminex HS Cytokine Panel A (Catalog # FCSTM09) for systematic differences when measuring a “panel” of IL-1β, TNF-α, and IL-10 vs. measuring “IL-10 only.” We selected 72 serum samples and assayed them in singleton 4 times: 2 separate “panel” batches, and 2 separate “IL-10 only” batches. Differences in log-transformed IL-10 results for sample replicates within and between the “panel” and “IL-10 only” batches were assessed for significance with paired t-tests (α=.01). We also assessed the differences graphically with Bland-Altman plots of differences and absolute percent differences.All batches included control materials from R&D Systems and internal lab serum pools (male and female). To retroactively assess the test batches, we graphically compared their quality control results to those of the subsequent, larger assay project we were piloting. Results: The “IL-10 only” assay yielded an average result of .879 pg/mL (SD .57) on batch 1 and .712 pg/mL (SD .58) on batch 2, with an average paired sample difference of .167 pg/mL, and an average absolute percent difference of 28.8%. The “panel” assay produced an average IL-10 result of .645 pg/mL (SD .50) on batch 1 and .720 pg/mL (SD .52) on batch 2, with an average paired sample difference of .075 pg/mL, and an average absolute percent difference of 15.5%. Comparing pooled IL-10 results from the “IL-10 only” batches with the “panel” batches, there was an average paired difference of .113 pg/mL and absolute percent difference of 16.2%. Paired t-testing of log-transformed results for within “panel,” within “IL-10 only,” and between pooled results from the two methods demonstrated that each had significant differences (p<.0001). The Bland-Altman plots further revealed that these differences were ubiquitously large for samples with low concentrations of IL-10.Test batch quality control results were consistent with those in the primary assay project. The serum pool QCs exhibited significant inter-assay variation – the male pool average result was .41 pg/mL (SD .10) vs. .359 in the test batches, and the female pool average was .57 pg/mL (SD .10) vs. .548 in the test batches. Conclusion: The multiplex assay had considerable inter-assay variation at low concentrations of IL-10, and low results were prevalent. Due to this, we determined that any methodological differences between the “panel” and “IL-10 only” methods were undetectable compared to ambient variation, and irrelevant given the sample characteristics. Presentation: 6/3/2024

Comparative study of erythrocyte sedimentation rate measurement between Celltac Alpha+ (MEK-1305) ESR Analyzer and standard Westergren method

Background: The Westergren method, a gold standard method for erythrocyte sedimentation rate (ESR) measurement, is one of the screening tests for routine clinical hematology that can be used as an inflammation marker. Since the results can be altered by numerous factors, new methodologies have been established to manage the possible pitfalls. Objective: This study compared erythrocyte sedimentation rate measurements obtained by the Celltac Alpha+ (MEK-1305) Automated Hematology and ESR analyzer with those obtained by the standard Westergren method. Materials and methods: The Celltac Alpha+ (MEK-1305) Automated Hematology and ESR analyzer was used to assess the performance of ESR measurement compared to the standard Westergren method. A total of 220 random EDTA whole blood samples from patients were included and analyzed in parallel using the automated analyzer and the standard Westergren method. Results: Spearman’s rank correlation coefficient (ρ = 0.916) obtained a good correlation between the two methods. In addition, the precision was good and acceptable according to the criteria, with a %CV of less than 10% in both intra-run and inter-run precision. There was no contamination between blood samples from using a single capillary probe. Moreover, Bland-Altman mean difference plot also indicated a good agreement, with a mean bias of -1.4 (95% CI: -0.8 to 2.1), an upper LOA of 7.6 (95% CI: 6.6 to 8.7) and a lower LOA = -10.5 (95% CI: -11.6 to -9.5). Conclusion: This comparative study indicated that the Celltac Alpha+ (MEK-1305) Automated Hematology and ESR analyzer is applicable within clinical routine practice along with proper measurement regulation. Even though the principles between these two methods are completely different, an acceptable interrelation was obtained due to the calibration process by Nihon Kohden corporation.

A veterinary-calibrated point-of-care glucometer accurately measures blood glucose concentration in dogs and cats.

To determine the clinical and analytical accuracy of a new veterinary-calibrated portable blood glucose monitor (PBGM) compared to a reference laboratory analyzer. Client-owned dogs (n = 77) and cats (n = 64). Peripheral and paired capillary whole-blood glucose concentrations measured via PBGM were compared to plasma glucose concentrations measured via a Cobas c501 reference analyzer (Roche). Analytical accuracy was evaluated with the Spearman rank correlation coefficient, Bland-Altman difference plot analysis, and Deming regression. Clinical accuracy was evaluated with Parkes error grid analysis. Paired peripheral and capillary blood samples were compared with the Wilcoxon matched-pairs signed-rank test. There was a high correlation between PBGM and reference analyzer readings in dogs and cats. Human quality assurance standards (International Organization for Standardization 15197:2013 guidelines) for analytical accuracy were met for 95% of feline peripheral blood samples and 89% of canine samples. Similar veterinary standards (American Society of Veterinary Clinical Pathology guidelines) were met for 89% of canine and 92% of feline peripheral blood glucose measurements. Error grid analysis showed that all peripheral canine and 97% of feline measurements were clinically accurate (zone A). Any altered clinical decision for the remaining feline measurements was expected to minimally impact outcome (zone B). No significant difference was found between peripheral and capillary blood glucose measurements in either species. The PBGM produced clinically accurate results and is suitable for use in veterinary and home settings to measure blood glucose.

Quantification of C1 inhibitor activity using a chromogenic automated assay: analytical and clinical performances.

The quantification of functional C1 inhibitor activity (fC1-INH) is an important tool to diagnose bradykinin-mediated angioedema (AE), whether hereditary or acquired. For that an accurate assay is necessary, therefore we evaluated the analytical performances of a fC1-INH chromogenic assay (Berichrom®, Siemens) performed utilizing an Optilite turbidimeter (Binding Site). fC1-INH was quantified by means of the chromogenic assay Berichrom®. Internal quality controls were used to determine the precision of the assay. Stability under various storage and matrix conditions, uncertainty, linearity, interference (of hemolysis, lipemia, and icterus), agreement with the manual Technochrom® assay, and diagnostic performances were further evaluated on samples from patients and healthy donors. The fC1-INH Berichrom® assay presented good performances regarding intra- and inter-assay precision (CV: 1.3-4.5 % and 3.0-6.0 %, respectively), expanded uncertainty (5.5 % at normal level and 12.5 % at the clinical threshold) and linearity (rho2>0.99: range 7-130 % activity). Addition of interfering substances (hemoglobin <16 g/L, intralipid® <12 g/L, and bilirubin <1 g/L) did not affect fC1-INH quantification. fC1-INH activity from healthy donors remained stable in citrate whole blood until 4 days at room temperature, and 7 days when plasma was collected. Agreement between the automated Berichrom® assay and the manual Technochrom® assay (n=47) was excellent as obtained with both quantitative (Deming regression and Bland-Altman difference plot) and qualitative (Kappa index=1) analyses. Finally, the diagnostic performance of the quantification of fC1-INH for AE evaluated on 81 patients revealed a sensitivity of 100 %, a specificity of 97.2 %, a positive predictive value of 83.3 % and a negative predictive value of 100 %. The automated fC1-INH Berichrom® assay showed good performance, both at the analytical and diagnostic/clinical levels that allowed its usage in a clinical laboratory for C1-INH-dependent bradykinin-mediated AE research in combination with quantitative C1-INH and C4 determinations.

A STUDY TO ESTABLISH THE AGREEMENT BETWEEN THE RESULTS OF ELECTROLYTES (SERUM SODIUM AND POTASSIUM) ESTIMATED BY A WET CHEMISTRY INSTRUMENT (EASYLYTE) WITH THAT OBTAINED BY A DRY CHEMISTRY ANALYZER (VITROS 350)

Objectives: The objective of the study was to assess the agreement between results of electrolytes (serum sodium and potassium) estimated by a wet chemistry instrument with that obtained by a dry chemistry analyzer. Methods: It was an observational analytical cross-sectional study done in the Departmental clinical laboratory. The samples were selected randomly from the usual lab workflow. All the samples were first run on the Easylyte (wet chemistry) and then run on the Vitros 350 (dry chemistry). The paired data thus obtained were compiled and tabulated and then statistically analyzed. Results: The agreement of the results between the two methods was evaluated using the Bland–Altman difference plot and the Passing–Bablok Regression Equation and the Deming regression studies. By analyzing the diagram of Bland–Altman, it is seen that for sodium, the average bias is of −2.22; limits of agreement being −26.12–21.77. For potassium, Bland Altman plots show a bias of −0.21; limits of agreement −0.61–0.19. Passing Bablock regression calculated an intercept of −56.86, 95% confidence interval (CI) (−100, −28) and Slope of 1.43 for sodium measurements and calculated an intercept of −0.706, 95% CI (−0.66, −0.45) and Slope of 1.2 for potassium estimation. Conclusion: Statistical analysis revealed conflicting solutions. There is a great discrepancy between the results of the electrolyte estimation by the two methods since the methodologies are not identical.

Assessment of MR blood-oxygen-level-dependent (BOLD) cerebrovascular reactivity under general anesthesia in children with moyamoya.

Moyamoya is a progressive, non-atherosclerotic cerebral arteriopathy that may present in childhood and currently has no cure. Early diagnosis is critical to prevent a lifelong risk of neurological morbidity. Blood-oxygen-level-dependent (BOLD) MRI cerebrovascular reactivity (CVR) imaging provides a non-invasive, in vivo measure of autoregulatory capacity and cerebrovascular reserve. However, non-compliant or younger children require general anesthesia to achieve BOLD-CVR imaging. To determine the same-day repeatability of BOLD-CVR imaging under general anesthesia in children with moyamoya. Twenty-eight examination pairs were included (mean patient age = 7.3 ± 4.0years). Positive and negatively reacting voxels were averaged over signals and counted over brain tissue and vascular territory. The intraclass correlation coefficient (ICC), Wilcoxon signed-rank test, and Bland-Altman plots were used to assess the variability between the scans. There was excellent-to-good (≥ 0.59) within-day repeatability in 18 out of 28 paired studies (64.3%). Wilcoxon signed-rank tests demonstrated no significant difference in the grey and white matter CVR estimates, between repeat scans (all p-values > 0.05). Bland-Altman plots of differences in mean magnitude of positive and negative and fractional positive and negative CVR estimates illustrated a reasonable degree of agreement between repeat scans and no systematic bias. BOLD-CVR imaging provides repeatable assessment of cerebrovascular reserve in children with moyamoya imaged under general anesthesia.

Can Automated 3-Dimensional Dixon-Based Methods Be Used in Patients With Liver Iron Overload?

Accurate quantification of liver iron concentration (LIC) can be achieved via magnetic resonance imaging (MRI). Maps of liver T2*/R2* are provided by commercially available, vendor-provided, 3-dimensional (3D) multiecho Dixon sequences and allow automated, inline postprocessing, which removes the need for manual curve fitting associated with conventional 2-dimensional (2D) gradient echo (GRE)-based postprocessing. The main goal of our study was to investigate the relationship among LIC estimates generated by 3D multiecho Dixon sequence to values generated by 2D GRE-based R2* relaxometry as the reference standard. A retrospective review of patients who had undergone MRI scans for estimation of LIC with conventional T2* relaxometry and 3D multiecho Dixon sequences was performed. A 1.5 T scanner was used to acquire the magnetic resonance studies. Acquisition of standard multislice multiecho T2*-based sequences was performed, and R2* values with corresponding LIC were estimated. The comparison between R2* and corresponding LIC estimates obtained by the 2 methods was analyzed via the correlation coefficients and Bland-Altman difference plots. This study included 104 patients (51 male and 53 female patients) with 158 MRI scans. The mean age of the patients at the time of scan was 15.2 (SD, 8.8) years. There was a very strong correlation between the 2 LIC estimation methods for LIC values up to 3.2 mg/g (LIC quantitative multiecho Dixon [qDixon; from region of interest R2*] vs LIC GRE [in-house]: r = 0.83, P < 0.01; LIC qDixon [from segmentation volume R2*] vs LIC GRE [in-house]: r = 0.92, P < 0.01); and very weak correlation between the 2 methods at liver iron levels >7 mg/g. Three-dimensional-based multiecho Dixon technique can accurately measure LIC up to 7 mg/g and has the potential to replace 2D GRE-based relaxometry methods.

Analytical performance of feline plasma on current Heska and IDEXX point-of-care biochemistry analyzers compared with a commercial laboratory analyzer.

Point-of-care (POC) biochemistry analyzers are widely used in small animal clinical practice but infrequently independently assessed for performance. To assess the performance of two current model point-of-care biochemistry analyzers (Heska Element DC and IDEXX Catalyst) compared with a commercial laboratory analyzer (Cobas 8000). One hundred twenty-one cats from a feline hospital population were sampled with plasma results from a single lithium heparin tube assessed on all three analyzers. Plasma biochemistry results from each POC analyzer were compared with the commercial laboratory analyzer using Bland-Altman difference plots and by determining whether the limits of agreement (LOAs) (95% of differences) fell within various quality goals after correcting for inherent bias. Only 7 of 14 analytes on the Heska analyzer and 2 analytes on the IDEXX analyzer attained the most stringent LOA quality goal, which was being within desirable total error based on biologic variation (TEdes). The number of analytes achieving quality goals increased with less stringent standards such as American Society of Veterinary Clinical Pathologists allowable total error (ASVCP TEA) guidelines or if <95% of clinical comparisons reaching these quality goals is considered acceptable. Widespread bias was found between both POC analyzers and the commercial laboratory analyzer. The performance of both POC biochemistry analyzers was variable compared with a commercial laboratory analyzer. Performance goals were only able to be attained after the bias for each analyzer was accounted for by offsetting the LOAs and quality goals set by the mean bias for each analyte on each analyzer.

Headspace versus direct injection for the quantitation of methanol, ethyl acetate, and fusel oils in distilled spirits by gas chromatography – Flame ionization detection

Distilled spirits can be very complex in their sensory or organoleptic compounds. Of significant interest is determination of the concentration of methanol, ethyl acetate, and fusel oils, which include n-propanol, isobutanol, n-butanol, active amyl (2-methyl-1-butanol) and isoamyl (3-methyl-1-butanol) alcohols. Here, we describe a validated method for the analysis of these analytes using a headspace (HS) sampling unit coupled with a gas chromatograph fitted with a flame ionization detector (GC/FID) for profiling these analytes in distilled spirits (n = 26) obtained from local retailers. HS results were compared to the direct injection (DI) GC/FID protocol made available by the US Alcohol and Tobacco Tax and Trade Bureau (TTB), method SSD:TM:200 via correlation and Bland-Altman difference plots to demonstrate that HS-GC/FID is a valid alternative to the direct injection protocols described elsewhere.•A method for the analysis of methanol, ethyl acetate, and fusel oils via headspace sampling coupled to a gas chromatograph fitted with a flame ionization detector (HS-GC/FID) is described.•Samples required no pre-treatment beyond diluting 1 mL of distilled spirit in 4 mL water containing table salt, which resulted in a method with minimal inlet or column maintenance, little sample prepration, and a rapid run time with retention times under 7 min.•Validation by comparing to established protocols using direct injection made available by the US Federal Tax and Trade Bureau (TTB).

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.

Ultrasound-derived fat fraction for detection of hepatic steatosis and quantification of liver fat content.

To compare ultrasound (US) and US-derived fat fraction (UDFF) with magnetic resonance proton density fat fraction (MRI-PDFF) for the detection of hepatic steatosis and quantification of liver fat content. Between October and December 2022, 149 patients scheduled for an abdominal MRI agreed to participate in this study and underwent MRI-PDFF, US and UDFF. Inclusion criteria were: (a) no chronic liver disease or jaundice; (b) no MRI motion artifacts; (c) adequate liver examination at US. Exclusion criteria were: (a) alcohol abuse, chronic hepatitis, cirrhosis, or jaundice; (b) MRI artifacts or insufficient US examination. The median of 10 MRI-PDFF and UDFF measurements in the right hepatic lobe was analyzed. UDFF and MRI-PDFF were compared by Bland-Altman difference plot and Pearson's test. Sensitivity, specificity, positive and negative predictive values, accuracy, and area under the receiver-operator curve (AUC-ROC) of US and UDFF were calculated using an MRI-PDFF cut-off value of 5%. p values ≤ 0.05 were statistically significant. 122 patients were included (61 men, mean age 60years, standard deviation 15years). The median MRI-PDFF value was 4.1% (interquartile range 2.9-6); 37.7% patients had a median MRI-PDFF value ≥ 5%. UDFF and MRI-PDFF had high agreement (p = 0.11) and positive correlation (⍴ = 0.81, p < 0.001). UDFF had a higher diagnostic value than US for the detection of steatosis, with AUC-ROCs of 0.75 (95% CI 0.65, 0.84) and 0.53 (95% CI 0.42, 0.64), respectively. UDFF reliably quantifies liver fat content and improves the diagnostic value of US for the detection of hepatic steatosis.

Reliable capillary sampling of carcinoembryonic antigen at home: the CASA feasibility study.

Follow-up after colorectal cancer requires frequent surveillance of the tumour marker carcinoembryonic antigen (CEA). Home-based blood sampling could be beneficial in terms of patients' well-being and societal cost-effectiveness. Blood sampling by venepuncture is unsuitable for home-based sampling. The aim of this feasibility study is to evaluate the long-term whole-blood stability of CEA. In this prospective feasibility study capillary blood withdrawal was collected in a Hem-Col® microtube containing a patented stabilization buffer using an internal lithium standard to correct for dilution. Long-term whole-blood stability was considered adequate if the relative bias in CEA concentration between delayed analysis of capillary samples and directly processed venepuncture is within the total error margin of CEA. Twenty two colorectal cancer patients were included to determine the stability of CEA in capillary sampling compared with directly processed (i.e. within 2h) venepuncture sampling. The median time between venous sampling and CEA analysis and capillary sampling and CEA analysis was 2h (interquartile range 1-4h) and 76 h (interquartile range 74-95 h), respectively. A Bland-Altman difference plot excluding outliers showed an overall relative bias of -1.23%. The two capillary samples in our outlier analysis also showed the highest lithium concentrations. Home-based capillary sampling with the use of the Hem-Col® buffer is a feasible method for CEA determination when analysed within 4 days after blood withdrawal, allowing monitoring for colorectal cancer patients from home. High lithium concentrations due to insufficient filling of the Hem-Col® tube suggest less reliable CEA measurements.

Evaluation of the interchangeability between the new fully-automated affinity chrome-mediated immunoassay (ACMIA) and the Quantitative Microsphere System (QMS) with a CE-IVD-certified LC-MS/MS assay for therapeutic drug monitoring of everolimus after solid organ transplantation.

This study aims to evaluate the interchangeability between the Siemens Healthineers' "EVRO" new affinity chrome-mediated immunoassay (ACMIA/EVRO) and Thermo Fisher Scientific's "EVER" Quantitative Microsphere System (QMS/EVER) with Chromsystems' CE-IVD-certified "MassTox" liquid-chromatography/tandem-mass spectrometry (LC-MS/MS) assay for the therapeutic drug monitoring of everolimus. A single lot of reagent, calibrators and controls were used for each assay. A total of 67 whole blood samples (n=67) from patients receiving solid organ transplant were analyzed (n=31 with kidney transplant and n=36 with liver transplant); Passing-Bablok regression and Bland-Altman difference plot were used to evaluate bias and individual agreement; LC-MS/MS analysis was used to measure the actual concentrations of calibrators and controls compared to the assigned value. ACMIA/EVRO did not show any systematic bias compared to LC-MS/MS (intercept=0.244ng/mL, 95% CI:-0.254 to 0.651ng/mL). Nevertheless, significant proportional bias (slope=1.511, 95% CI: 1.420 to 1.619) associated to a combined bias of 44.8% (95% CI: 41.2-48.3%) was observed. Conversely, QMS/EVER did not show any bias at both systematic (intercept=-0.151ng/mL, 95% CI:-0.671 to 0.256ng/mL) and proportional level (slope=0.971, 95% CI: 0.895 to 1.074) with a non-statistically significant combined bias of-3.6% (95% CI:-8.4-1.1%). Based on a concentration of calibrators and controls above the assigned value for both the analytical methods, in the ACMIA/EVRO a correction which was approximately one-third of the correction for the QMS/EVER was observed. ACMIA/EVRO but not QMS/EVER shows a lack of interchangeability with the CE-IVD-certified LC-MS/MS assay. We hypothesize that, as the ACMIA/EVRO uses an anti-sirolimus antibody, the under-corrected assigned value in the assay calibrators was not sufficient to reproduce the everolimus metabolites cross-reactivity occurring in real samples.

Can scene bloodstains be used to quantify drug concentration at the moment of injury?

Blood is the primary material for quantitative toxicological analysis and interpretation of the results. However, in some cases like hit-and-run, it may be collected after a long time since the incident, resulting in the complete elimination or a significant decrease in the concentrations of potentially present drugs. If the suspect was injured and bloodstains were revealed, they can become the best or sometimes, the only material to be used to prove driving under the influence of drugs. In this context, the aim of this work was to develop a simple procedure that would allow for the estimation of drug concentrations in forensic bloodstains of unknown volume. In this work endogenous amino acids: valine and leucine were used to determine the unknown volume of blood from which the stain was formed. In order to isolate the analytes from bloodstains on different surfaces (plastic and cotton) the elution mixture consisted of an acetonitrile: water (60:40) and sodium chloride (0.9%) was used. The developed protocol was tested on 32 authentic forensic samples (mostly cases of people driving under the influence of amphetamine). The results of bloodstains analyses were compared with the results of whole blood analyses. The accuracy was in the range from −87.7 to +471.0%. However, for most of the cases, more accurate results were obtained. The differences between amphetamine values estimated from bloodstains and determined from whole blood were analysed using the Bland-Altman difference plots that revealed significant agreement. The variables concentrations estimated from bloodstains and concentrations calculated from whole blood were found to be strongly correlated. The Pearson correlation coefficients were: for plastic r(29) = 0.85 and for cotton r(25) = 0.91. This is the first work in which quantitative analyses of drugs in bloodstains have been attempted. A special protocol was developed for this purpose. The conducted research indicates that estimation of the concentration of drugs in bloodstains from the blood of an unknown volume is possible. The developed protocol has been extensively tested on authentic forensic samples and the obtained results were successfully compared with drug concentrations determined in whole blood. Nevertheless, the proposed method of estimating drug concentrations in bloodstains is characterized by many disadvantages, and the determined values should be treated with great caution, at best as estimates.

Rate of Change of Liver Iron Content by MR Imaging Methods: A Comparison Study.

Objective: Magnetic resonance imaging (MRI) can accurately quantify liver iron concentration (LIC), eliminating the need for an invasive liver biopsy. Currently, the most widely used relaxometry methods for iron quantification are R2 and R2*, which are based on T2 and T2* acquisition sequences, respectively. We compared the rate of change of LIC as measured by the R2-based, FDA-approved commercially available third-party software with the rate of change of LIC measured by in-house analysis using R2*-relaxometry-based MR imaging in patients undergoing follow-up MRI scans for liver iron estimation. Methods: We retrospectively included patients who had undergone serial MRIs for liver iron estimation. The MR studies were performed on a 1.5T scanner; standard multi-slice, multi-echo T2- and T2*-based sequences were acquired, and LIC was estimated. The comparison between the rate of change of LIC by R2 and R2* values was performed via correlation coefficients and Bland–Altman difference plots. Results: One hundred and eighty-nine MR abdomen studies for liver iron evaluation from 81 patients (male: 38; female: 43) were included in the study. Fifty-nine patients had two serial scans, eighteen patients had three serial scans, three patients had four serial scans, and one patient had five serial scans. The average time interval between the first and last scans for each patient was 13.3 months. The average rates of change of LIC via R2 and R2* methods were −0.0043 ± 0.0214 and −0.0047 ± 0.012 mg/g per month, respectively. There was no significant difference in the rate of change of LIC observed between the two methods. Linearity between the rate of change of LIC measured by R2 (LIC R2) and R2* (LIC R2*) was strong, showing a correlation coefficient of r = 0.72, p < 0.01. A Bland–Altman plot between the rate of change of the two methods showed that the majority of the plotted variables were between two standard deviations. Conclusion: There was no significant difference in the rate of change of LIC detected between the R2 method and the R2* method that uses a gradient echo (GRE) sequence acquired with breath-hold. Since R2* is relatively faster and less prone to motion artifacts, R2*-derived LIC is recommended for iron homeostasis follow-up in patients with liver iron overload.

Quantification of Hepatic Steatosis by Ultrasound: Prospective Comparison With MRI Proton Density Fat Fraction as Reference Standard.

BACKGROUND. Multiple ultrasound platforms now provide quantitative measures of hepatic steatosis. One such measure is the ultrasound-derived fat fraction (UDFF), which combines attenuation and backscatter quantification. OBJECTIVE. The purpose of this study was to characterize agreement between UDFF and MRI proton-density fat fraction (PDFF) measurements. METHODS. This prospective cross-sectional study enrolled 56 overweight and obese adolescents and adults (age ≥ 16 years) who underwent investigational ultrasound (deep abdominal transducer) and MRI examinations of the liver during a single visit from August 2020 to October 2020. Ultrasound examinations included three UDFF acquisitions of five measurements each (15 measurements total), and an overall median of medians was computed (UDFFoverall). MRI examinations included three PDFF acquisitions with calculation of an overall median PDFF. Spearman rank-order correlation was computed between UDFF and MRI PDFF measurements. Intraclass correlation coefficients and Bland-Altman difference plots were used to assess agreement. ROC curves were used to assess diagnostic performance of UDFF for detecting MRI PDFF of 5.5% or more. RESULTS. Median participant age was 32.5 years (IQR, 24.0-39.0 years); 40 participants were female, and 16 were male. A total of 34 (60.7%) participants had an MRI PDFF of 5.5% or more. UDFFoverall was 10.5% (IQR, 5.0-20.0%); median MRI PDFF was 6.1% (IQR, 3.4-13.7%). UDFFoverall was positively associated with MRI PDFF (ρ, 0.82; p < .001; intraclass correlation coefficient, 0.84 [95% CI, 0.59-0.93]). Mean bias between UDFF and PDFF was 4.0% (95% limits of agreement, -7.9% to 15.9%), with similar bias if summarizing UDFF by the first five measurements (4.4%), first three measurements (4.4%), or first measurement (4.6%). UDFFoverall AUC was 0.90 (95% CI, 0.79-0.96) for MRI PDFF of 5.5% or more; AUC was not significantly different when it was based on the number of UDFF measurements (p = .11-.97 for all pairwise AUC comparisons). UDFFoverall cutoff of more than 5% had sensitivity of 94.1% and specificity of 63.6% for diagnosing MRI PDFF of 5.5% or more. CONCLUSION. Measurements of hepatic steatosis using UDFF show strong agreement with measurements by MRI PDFF. A UDFFoverall cutoff of more than 5% provides high AUC and sensitivity, albeit low specificity, for detection of MRI PDFF of 5.5% or more. CLINICAL IMPACT. UDFF may have a clinical role in detection of hepatic steatosis. A reduced number of individual measurements is likely sufficient for determining an overall UDFF value. TRIAL REGISTRATION. ClinicalTrials.gov: NCT04523584.

Remote capillary blood collection for HbA1c measurement during the COVID-19 pandemic: A laboratory and patient perspective.

AimsThe purpose of this study was to assess the clinical performance and user acceptance of capillary blood samples prepared remotely using the MiniCollect® capillary blood collection device as an alternative to blood collection by venepuncture for glycated haemoglobin (HbA1c) analysis.MethodsFollowing written informed consent, a cross‐sectional study was conducted in individuals aged ≥18 years with any type of diabetes who routinely self‐monitor their blood glucose. Eligible participants recruited whilst attending their routine clinical appointments were required to provide a venous blood sample, prepare a capillary blood sample at home (remotely) and complete a bespoke questionnaire. HbA1c in whole blood collected in ethylenediaminetetraacetic acid was determined by capillary electrophoresis on the Sebia Capillary's 3 Tera analyser following standard operating procedure.ResultsHbA1c results from both venous and capillary collection demonstrated good agreement. Passing‐Bablok regression: y = 0 + 1x (p = 0.18), Spearman correlation r = 0.986, p < 0.0001. The Bland–Altman difference plot provided a mean difference of 0.3 mmol/mol (2.2%). Over half of the participants found the MiniCollect device easy to use. The majority of participants were in favour of the remote capillary blood collection service and would use it if routinely available.ConclusionThe home collection of capillary blood for HbA1c determination is a valuable and convenient alternative to standard venous blood collection as it provides an opportunity to support routine HbA1c monitoring, whilst mitigating the transmission of SARS‐CoV‐2. This service would additionally allow individuals to attend clinic visits with a HbA1c value, ensuring optimal continuance of patient care for individuals with diabetes.

Comparison of blood collection tubes for 29 biochemical analytes in pediatric patients with central venous catheters

BackgroundPediatric cancer patients undergoing chemotherapy or radiation therapy generally require a central venous catheter (CVC). However, serum drawn from CVCs has several drawbacks for use in routine chemistry tests. Biochemical analytes were evaluated using heparin plasma instead of serum to maintain turnaround time and to prevent problems caused by micro-clot formation or delayed clotting time. MethodsVenous blood samples from 52 pediatric oncology patients with chemoports or Hickman catheters were collected in serum separating tubes (SSTs) and lithium heparin tubes (LHTs). A total of 29 parameters were analyzed on a Cobas c702 (Roche Diagnostics, Mannheim, Germany). Passing-Bablok regression and Bland-Altman difference plots were used for statistical analyses. ResultsWhen the mean value of each analyte measured from LHT was compared with those from SST, percentage bias was within the desirable bias limit in most of the analytes. However, albumin, potassium, and inorganic phosphorus showed a negative constant bias of −3.0%, −5.3%, and −1.6%, respectively, and total protein showed a positive constant bias of + 3.8%. ConclusionsThe use of LHTs for sample collection from pediatric patients with CVCs could be helpful for routine chemistry analyses. The results of potassium and total protein should be interpreted with consideration of the difference between serum and plasma samples.

Comparison of three hematocrit measurement methods in the southern white rhinoceros (Ceratotherium simum simum).

BackgroundHematocrit (HCT) determination is an integral part of health and disease assessments in captive and wild white rhinoceroses. Several affordable automated hematology analyzers have been developed for in‐clinic and field use and have the advantage of being able to measure a large number of additional measurands. However, the accuracy of these analyzers for rhinoceros HCT measurements has not yet been investigated.ObjectivesWe aimed to compare the HCT results generated by the EPOC portable analyzer system and the Abaxis VetScan HM5 with the gold standard of a manual packed cell volume (PCV) measured using the microhematocrit method.MethodsHematocrits were measured with the EPOC and the Abaxis VetScan HM5 (bovine setting) and compared with the PCVs of 69 white rhinoceros whole blood samples. Results were compared using Bland–Altman difference plots and Passing‐Bablok regression analysis. A total allowable analytical error of 10% was set as the performance goal.ResultsA significant positive bias, with a mean of 7.7% for the EPOC and 17.9% for the Abaxis, was found compared with the manual PCV method.ConclusionsThe allowable error goal of 10% was not exceeded with the EPOC analyzer. Although not analytically equivalent to the gold standard, the EPOC results could therefore be used as approximations in critical situations where manual measurements cannot be performed. The Abaxis exceeded this allowable error and overestimated HCTs in rhinoceroses. Therefore, method‐specific reference intervals should be used.

Comparison of smartphone application-based visual acuity with traditional visual acuity chart for use in tele-ophthalmology

PURPOSE:The aim of this study was to compare the visual acuity (VA) by smartphone-based applications – EyeChart and the Peek Acuity to the standard Snellen chart to explore the possibility of using them as an alternative in tele-ophthalmology in the current COVID-19 pandemic.MATERIALS AND METHODS:An analytical type of observational study was done on 360 eyes of 184 patients above 18 years of age. Patients with VA <6/60 and gross ocular pathology were excluded from the study. VA measured by these three methods was converted to logMAR scale for ease of statistical analysis. One-way analysis of variance with post Tukey HSD was used to compare the VA measured by these three methods.RESULTS:There was no statistically significant difference between VA measured using the smartphone-based apps (EyeChart and Peek Acuity) and the Snellen chart (F = 2.5411, P = 0.7925) in 360 eyes assessed. VA measured by Peek Acuity (P = 0.5225) was more comparable to Snellen chart than EyeChart (P = 0.4730). Intraclass correlation coefficient (ICC) demonstrated a strong positive correlation for EyeChart (ICC: 0.982, P < 0.001) and Peek Acuity (ICC: 0.980, P < 0.001) with Snellen chart. A Bland–Altman difference plot showed good limits of agreement for both EyeChart and Peek Acuity with Snellen chart. In subgroup analysis, VA measured by Peek Acuity was not statistically different from Snellen in any subgroups, but in EyeChart, it was statistically different in emmetropes.CONCLUSION:VA measured by smartphone apps (EyeChart and Peek Acuity) was comparable with traditional Snellen chart and can be used as an effective, reliable, and feasible alternative to assess VA in tele-ophthalmology.