Deming Regression Research Articles

Development of a high-throughput SARS-CoV-2 antibody testing pathway using dried blood spot specimens

BackgroundSerological assays for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) have roles in seroepidemiology, convalescent plasma-testing, antibody durability and vaccine studies. Currently, SARS-CoV-2 serology is performed using serum/plasma collected by venepuncture. Dried blood spot (DBS) testing offers significant advantages as it is minimally invasive, avoids venepuncture with specimens being mailed to the laboratory.MethodsA pathway utilizing a newborn screening laboratory infrastructure was developed using an enzyme-linked immunosorbent assay to detect IgG antibodies against the receptor-binding domain of the SARS-CoV-2 spike protein in DBS specimens. Paired plasma and DBS specimens from SARS-CoV-2 antibody-positive and -negative subjects and polymerase chain reaction positive subjects were tested. DBS specimen stability, effect of blood volume and punch location were also evaluated.ResultsDBS specimens from antibody-negative (n = 85) and -positive (n = 35) subjects and polymerase chain reaction positive subjects (n = 11) had a mean (SD; range) optical density (OD) of 0.14 (0.046; 0.03–0.27), 0.98 (0.41; 0.31–1.64) and 1.12 (0.37; 0.49–1.54), respectively. An action value OD >0.28 correctly assigned all cases. The weighted Deming regression for comparison of the DBS and the plasma assay yielded: y = 0.004041 + 1.005x, r = 0.991, Sy/x 0.171, n = 82. Extraction efficiency of antibodies from DBS specimens was >99%. DBS specimens were stable for at least 28 days at ambient room temperature and humidity.ConclusionsSARS-CoV-2 IgG receptor-binding domain antibodies can be reliably detected in DBS specimens. DBS serological testing offers lower costs than either point of care or serum/plasma assays that require patient travel, phlebotomy and hospital/clinic resources; the development of a DBS assay may be particularly important for resource poor settings.

Assessment of a dried blood spot C-reactive protein method to identify disease flares in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is characterised by painful, stiff and swollen joints. RA features sporadic ‘flares’ or inflammatory episodes—mostly occurring outside clinics—where symptoms worsen and plasma C-reactive protein (CRP) becomes elevated. Poor control of inflammation results in higher rates of irreversible joint damage, increased disability, and poorer quality of life. Flares need to be accurately identified and managed. A method comparison study was designed to assess agreement between CRP values obtained by dried blood spot (DBS) versus conventional venepuncture sampling. The ability of a weekly DBS sampling and CRP test regime to detect flare outside the clinic was also assessed. Matched venepuncture and finger lancet DBS samples were collected from n = 100 RA patients with active disease at baseline and 6 weeks (NCT02809547). A subset of n = 30 RA patients submitted weekly DBS samples over the study period. Patient demographics, including self-reported flares were recorded. DBS sample CRP measurements were made by enzyme-linked immunosorbent assay, and venepuncture samples by a reference immunoturbometric assay. Data was compared between sample types by Bland–Altman and weighted Deming regression analyses. Flare detection sensitivity and specificity were compared between ‘minimal’ baseline and 6 week sample CRP data and the ‘continuous’ weekly CRP data. Baseline DBS ELISA assay CRP measures yielded a mean positive bias of 2.693 ± 8.640 (95% limits of agreement − 14.24 to 19.63%), when compared to reference assay data. Deming regression revealed good agreement between the DBS ELISA method and reference assay data, with baseline data slope of 0.978 and intercept -0.153. The specificity of ‘continuous’ area under the curve (AUC) CRP data (72.7%) to identify flares, was greater than ‘minimal’ AUC CRP data (54.5%). This study indicates reasonable agreement between DBS and the reference method, especially at low to mid-range CRP values. Importantly, longitudinal CRP measurement in RA patients helps to clearly identify flare and thus could assist in remote monitoring strategies and may facilitate timely therapeutic intervention.Trial registration: The Remote Arthritis Disease Activity MonitoR (RADAR) study was registered on 22/06/2016 at ClinicalTrials.gov Identifier: NCT02809547. https://clinicaltrials.gov/ct2/show/NCT02809547.

Time series prediction of under-five mortality rates for Nigeria: comparative analysis of artificial neural networks, Holt-Winters exponential smoothing and autoregressive integrated moving average models

BackgroundAccurate forecasting model for under-five mortality rate (U5MR) is essential for policy actions and planning. While studies have used traditional time series modeling techniques (e.g., autoregressive integrated moving average (ARIMA) and Holt-Winters smoothing exponential methods), their appropriateness to predict noisy and non-linear data (such as childhood mortality) has been debated. The objective of this study was to model long-term U5MR with group method of data handling (GMDH)-type artificial neural network (ANN), and compare the forecasts with the commonly used conventional statistical methods—ARIMA regression and Holt-Winters exponential smoothing models.MethodsThe historical dataset of annual U5MR in Nigeria from 1964 to 2017 was obtained from the official website of World Bank. The optimal models for each forecasting methods were used for forecasting mortality rates to 2030 (ending of Sustainable Development Goal era). The predictive performances of the three methods were evaluated, based on root mean squared errors (RMSE), root mean absolute error (RMAE) and modified Nash-Sutcliffe efficiency (NSE) coefficient. Statistically significant differences in loss function between forecasts of GMDH-type ANN model compared to each of the ARIMA and Holt-Winters models were assessed with Diebold-Mariano (DM) test and Deming regression.ResultsThe modified NSE coefficient was slightly lower for Holt-Winters methods (96.7%), compared to GMDH-type ANN (99.8%) and ARIMA (99.6%). The RMSE of GMDH-type ANN (0.09) was lower than ARIMA (0.23) and Holt-Winters (2.87). Similarly, RMAE was lowest for GMDH-type ANN (0.25), compared with ARIMA (0.41) and Holt-Winters (1.20). From the DM test, the mean absolute error (MAE) was significantly lower for GMDH-type ANN, compared with ARIMA (difference = 0.11, p-value = 0.0003), and Holt-Winters model (difference = 0.62, p-value< 0.001). Based on the intercepts from Deming regression, the predictions from GMDH-type ANN were more accurate (β0 = 0.004 ± standard error: 0.06; 95% confidence interval: − 0.113 to 0.122).ConclusionsGMDH-type neural network performed better in predicting and forecasting of under-five mortality rates for Nigeria, compared to the ARIMA and Holt-Winters models. Therefore, GMDH-type ANN might be more suitable for data with non-linear or unknown distribution, such as childhood mortality. GMDH-type ANN increases forecasting accuracy of childhood mortalities in order to inform policy actions in Nigeria.

Method comparison between real-time spectral and laboratory based measurements of moisture content and CIELAB color pattern during dehydration of beef slices

In this study, partial least square (PLS) regression models were developed to predict moisture content (MC) (model 1), CIELAB color (model 2) or all four parameters (model 3) of beef slices during drying. Model development was based on data from two measurement campaigns of MC (%), CIELAB L*, a* and b*values and hyperspectral data in the range of 500–1009 nm. To increase the robustness of the models, the beef samples varied dependent on cattle breed, cut and pre-treatment. With low-cost, non-invasive continuous monitoring systems in mind, the models were simplified by wavelengths selection. The Deming and Passing-Bablok regression and the Bland-Altman plot revealed high model performances. Mean differences (full/reduced model) of −0.64/-0.64 for MC, −0.14/-0.15 for CIELAB L*, 0.05/0.04 for a* and 0.08/0.06 for b* values were achieved for model 3, which shows the high potential for simple real-time monitoring applications combining all investigated factors and parameters. • Robust models for spectral measurements of moisture and color during drying of beef. • High accordance between spectral and laboratory measurements. • Simplified high performance models by selection of maximum ten wavelengths. • High potential of simple non-invasive spectral monitoring systems for beef drying.

Validation of the BD FACSPresto system for the measurement of CD4 T-lymphocytes and hemoglobin concentration in HIV-negative and HIV-positive subjects

This study aimed to compare the performance of the BD FACSPresto system with the conventional standard-of-care technologies for the measurement of absolute CD4 count (AbsCD4), CD4 percentage (CD4%) and total hemoglobin concentration (Hb) in capillary and venous blood samples of HIV-negative and HIV-positive subjects. A total of 1304 participants were included in this prospective cohort study. Both venous and capillary blood samples were analyzed using the BD FACSPresto system and the results were compared against the BD FACSCalibur for enumerating AbsCD4 and CD4% and Sysmex XT-4000i hematology analyzer for determining Hb levels. Method comparison studies were performed using Deming regression and Bland–Altman plots. The Deming regression analyses comparing the accuracy of the BD FACSPresto system with the reference standard technologies demonstrated a significant linear correlation between the AbsCD4, CD4%, and Hb values generated by the two platforms. The 95% CI of the slopes for AbsCD4, CD4%, and Hb levels were 0.94–0.99, 0.99–1.01 and 0.86–0.93, respectively (P < 0.001). Bland–Altman plots for AbsCD4, CD4%, and Hb levels demonstrated close agreement between the BD FACSPresto system and the reference standards for all study participants. The performance and accuracy of BD FACSPresto system was comparable to the reference standard technologies. The BD FACSPresto system can be used interchangeably with BD FACSCalibur platform for CD4 and Sysmex XT-4000i hematology analyzer for Hb concentrations in resource-limited settings thus, improving accessibility to point-of-care testing services.

NeuMoDx random access molecular diagnostic system for detection and quantification of hepatitis B virus in clinical samples.

Currently, several molecular assays are available to detect and quantify HBV DNA in clinical samples. We aimed to characterize and compare the clinical performance of newly designed NeuMoDx PCR to the existing artus PCR. The plasma HBV DNA levels of 96 clinical and 5 external quality control samples were measured by NeuMoDx and artus assays simultaneously in Kocaeli University, Turkey. The linearity, agreement and the correlation between two assays were determined by Deming regression analysis, Bland-Altman plotting, the chi-square and the relative absolute error statistical analyzes. For all statistical analyzes, the XLSTAT statistical program was used. The mean (standard deviation; SD) age was 45.07 ± 12.29. HBsAg S/Co median (range) was 4,273.4 ± 1,138.1 and ALT U/L median (range) was 27 ± 16. The mean (SD) of HBV DNA was 1.46+E6 ± 1.0+E4 for NeuMoDx and 1.54+E5 ± 4.7 + E4 for artus assays. The Deming regression indicates a linear correlation (95% confidence). The chi-square test indicates strong correlation (p < 0.001). Bland-Altman analysis confirms that the measurement difference is acceptable. The relative absolute error analysis for artus showed relatively less and more consistent error rate. With 5 external quality check samples, the statistical significance was low (p = 0.566). The NeuMoDx HBV assay showed an excellent analytical performance by providing a rapid, high throughput technology in a random-access testing system in clinical samples and may be a new solution for viral load quantification in the management of HBV infections.

Comparison of Heat Fractionation and Gel Electrophoresis Methods for the Quantitative Determination of Alkaline Phosphatase Isoenzymes

Abstract Introduction Alkaline phosphatase (ALP) is important in the diagnostic work-up for hepatobiliary and bone diseases. ALP isoenzymes are expressed in the bone, liver, kidney, placenta, and intestine, and vary in heat stability and electrophoretic mobility. Distinguishing the different ALP isoenzymes is clinically important for the diagnosis of pathologies associated with elevated ALP activity. Current modalities available to measure ALP isoenzymes utilize the heat stability, electrophoretic mobility, and immunochemical properties of the isoenzymes. The differences inherent in these methods allow for unique benefits of each method in identifying ALP isoenzymes. The objective of this study was to compare bone, liver, and placental ALP isoenzyme results determined by heat fractionation and gel electrophoresis and to characterize the heat-stable non-liver fraction (t1/2 &amp;gt;11 min), reported by heat fractionation, using gel electrophoresis. Methods A total of 72 de-identified serum samples that span a wide range of known ALP isoenzyme concentrations and disease states were used to measure ALP using gel electrophoresis and heat fractionation. Heat fractionation was achieved by selective inactivation of the isoenzymes at 56 °C in 10, 15, and 20-minute intervals. Log-percent activity of the total and heat-inactivated fractions at each time point was plotted against time in minutes. The linear activity decay between 10 and 20 minutes determined the relative amount of liver isoenzyme activity and the slope of the line determined the half-lives of ALP isoenzymes. Electrophoresis was performed according to the manufacturer’s protocol using the Hydragel ISO-PAL gel to resolve ALP isoenzymes based on their electrophoretic mobility and interaction with lectin. ALP isoenzymes were quantified by densitometry. Results Our results show a significant correlation coefficient (r) of 0.98, Deming regression slope of 1.1, and bias of -1.2% for the liver isoenzyme (n=43). However, liver fractions are not distinguishable by heat fractionation when heat-stable isoforms are present. The bone fraction (n=43) showed a coefficient of correlation of 0.86, slope of 0.55, and bias of -31%. Although, with a small sample size (n=6), the placental isoenzyme showed a significant agreement between the two methods: r = 0.999, slope = 0.98, and a -3.5% bias. Of the non-liver fractions reported by heat fractionation (n=13, ALP &amp;gt;100 U/L) eleven (85%) showed distinct qualitative bands in the intestinal lane on gel electrophoresis; however, quantitative values did not correlate between the two methods. Conclusion Our data support an agreement between the heat fractionation and gel electrophoresis methods for the quantitative determination of liver and placental alkaline phosphatase isoenzymes. Although there is an association between the two methods, the activity of the bone isoenzyme was underestimated by the gel electrophoresis method, likely due to saturation of the gel and densitometry scan because of elevated protein concentrations. The non-liver fractions were qualitatively identified as intestinal isoenzyme.

Analytical bias of automated immunoassays for six serum steroid hormones assessed by LC-MS/MS.

IntroductionThere is a growing amount of evidence showing the significant analytical bias of steroid hormone immunoassays, but large number of available immunoassays makes conduction of a single comprehensive study of this issue hardly feasible. Aim of this study was to assess the analytical bias of six heterogeneous immunoassays for serum aldosterone, cortisol, dehydroepiandrosterone sulphate (DHEAS), testosterone, 17-hydroxyprogesterone (OHP) and progesterone using the liquid chromatography coupled to the tandem mass spectrometry (LC-MS/MS).Materials and methodsThis method comparison study included 49 serum samples. Testosterone, DHEAS, progesterone and cortisol immunoassays were performed on the Abbott Architect i2000SR or Alinity i analysers (Abbott Diagnostics, Chicago, USA). DiaSorin’s Liaison (DiaSorin, Saluggia, Italy) and DIAsource’s ETI-Max 3000 analysers (DIAsource ImmunoAssays, Louvain-La-Neuve, Belgium) were chosen for aldosterone and OHP immunoassay testing, respectively. All immunoassays were evaluated against the LC-MS/MS assay relying on the commercial kit (Chromsystems, Gräfelfing, Germany) and LCMS-8050 analyser (Shimadzu, Kyoto, Japan). Analytical biases were calculated and method comparison was conducted using weighted Deming regression analysis.ResultsDepending on the analyte and specific immunoassay, mean relative biases ranged from -31 to + 137%. Except for the cortisol, immunoassays were positively biased. For none of the selected steroids slope and intercept 95% confidence intervals simultaneously contained 0 and 1, respectively.ConclusionsEvaluated immunoassays failed to satisfy requirements for methods’ comparability and produced significant analytical biases in respect to the LC-MS/MS assay, especially at low concentrations.

Improved Sample Quality and Decreased Turnaround Time When Using Plasma Blood Collection Tubes with a Mechanical Separator in a Large University Hospital.

Serum is commonly used for clinical chemistry testing but many conditions can affect the clotting process, leading to poor sample quality and impaired workflow. With serum gel tubes, we found a high proportion of sample probe aspiration errors on our Beckman AU5800 analyzers. We decided to implement the BD Barricor™ plasma tubes, and we validated an off-specification centrifugation scheme and verified that results obtained for 65 chemistry and immunochemistry tests were comparable to those obtained in serum gel tubes. Finally, we evaluated the impact of this new tube on sample error rate and laboratory turnaround time. To validate centrifugation settings, 50 paired samples were collected in Barricor tubes and centrifuged at 1912 × g for 10 min or 5 min (off-specification). To compare serum gel tubes with Barricor plasma tubes, 119 paired samples were collected from volunteers and results were analyzed using weighed Deming regression. Finally, the proportion of aspiration errors and laboratory TAT for potassium were measured before and after implementing Barricor tubes. Barricor tubes showed clinically acceptable equivalence to serum gel tubes for the studied analytes, and the off-specification centrifugation scheme did not affect the results. Implementing Barricor tubes improved the laboratory workflow by decreasing the aspiration error rates (2.01% to 0.77%, P < 0.001) and lowering hemolysis (P < 0.001). The laboratory TAT for potassium were also significantly lowered (P < 0.001). Use of Barricor tubes instead of serum gel tubes leads to better sample quality, shorter more reproducible laboratory TAT, and decreases costs associated with error management.

Designing and evaluating analytical parameters to adapt siemens urinary creatinine enzymatic method to open system analysers

Urinary creatinine is measured to assess kidney function and also as part of sample validity testing in drugs of abuse. Creatinine methods based on alkaline picrate Jaffe’s reaction require extra cleaning on chemistry analysers to minimise any interference from picric acid and sodium hydroxide on other reagents on board. Enzymatic methods reagents are not as invasive and more specific. Siemens enzymatic method is more sensitive and specific when compared to Thermo Fisher alkaline picrate method but there were no available analytical parameters to setup the Siemens enzymatic method on Beckman-Coulter AU5800 analyser as an open system analyser. Emulating setup parameters from Siemens chemistry analysers did not work. The analytical parameters were developed through systematic testing using different settings to adopt and optimise the method. A full correlation was performed using the developed parameters with alkaline picrate method. The Deming regression weighted analysis for 438 samples showed a good correlation at a 95% confidence interval. Slope is 1.029 to 1.041, Y-intercept when X=0.0 is -0.9156 to -0.7481 and correlation coefficient (r) is 0.998. Alkaline picrate method Mean and SD is 12.059 and 7.248 respectively and for the Enzymatic method is 11.653 and 7.504 respectively. Many interferences from drugs and other substances are eliminated when using the enzymatic method and the stability of other reagents on-board improved because the reagents used in the enzymatic method are less invasive.

Comparison of canine urine specific gravity measurements between various refractometers in a clinical setting.

Veterinary facilities might use multiple refractometers and individuals to measure urine specific gravity (USG). Previous comparison studies show conflicting results. Furthermore, the clinical significance of measurement differences and interobserver variabilities has not been assessed. We aimed to determine statistically and clinically significant differences between four refractometers in measuring canine USG and subsequent categorization of urine concentrations and azotemia and determine the variability between different observers performing USG measurements. Fifty-nine specimens were included for the USG measurements with four refractometers by different observers. Each refractometer pair was compared using Spearman's rank correlation, Bland-Altman difference plots, and Deming regression analyses. Calculated bias was compared to set performance goals. Interobserver agreement was evaluated, and intraclass correlation coefficients were used to determine differences in the categorization of urine concentrations and azotemia (prerenal or renal). There was excellent correlation (rs =.99-1.00) between refractometers. All comparisons involving R4 showed significant constant and proportional biases. Mean bias met the clinical performance goals for all refractometers, except for comparisons with R4, where up to 17 results were outside the allowable bias. There was almost perfect agreement (rs =.999) between observers and excellent agreement (ICC=.96-.99) for the classification of urine concentrations. In azotemic patients (22%), there was perfect agreement (ICC=1.00) for the categorization of azotemia. In most cases, three of the refractometers evaluated in this study can be used interchangeably at all USG values, without affecting clinical decision-making. Multiple observers did not significantly affect decision-making.

Abstract 6483: Performance characteristics of the first FDA-cleared droplet digital PCR (ddPCR) IVD assay for monitoring chronic myelogenous leukemia

Abstract Introduction: Chronic myelogenous leukemia (CML) is a cancer of myeloid cells that accounts for 15-20% of all cases of leukemia. Most CML cases are caused by a translocation between chromosomes 9 and 22 which creates an abnormal fusion gene, BCR-ABL1. The BCR-ABL1 gene expresses an abnormal tyrosine kinase protein that causes unregulated growth and survival of granulocytes. CML is treated with TKIs (tyrosine kinase inhibitors). The concentration of BCR-ABL1 transcript RNA is a marker of disease progression and the effectiveness of TKI treatment.Bio-Rad's QXDx BCR-ABL %IS Kit is an in vitro diagnostic test for the quantification of BCR-ABL transcripts in total RNA from whole blood from individuals diagnosed with Chronic Myeloid Leukemia expressing BCR-ABL1 Fusion transcript types e13a2 and/or e14a2. Materials and Methods: The QXDx BCR-ABL %IS Kit is a newly launched FDA-approved ddPCR assay from Bio-Rad Laboratories. Reproducibility of results across multiple sites, days, instruments, and users was evaluated using contrived samples consisting of BCR-ABL positive patient samples mixed with negative patient samples. Clinical performance of the kit was evaluated on patient samples, and compared to an already existing FDA-approved test. Clinical performance was further tested in the College of American Pathologists challenge. Results: The reproducibility study noted negligible contributions to variance from site, instrument, day, and user for samples spanning from MR 0.7-4.2. The mean between the QXDx™ BCR-ABL %IS Kit and the comparator test using a Bland-Altman analysis was 0.16 MR units. The limits of agreement between the two methods indicate that the difference between the two methods should be between 0.47 and -0.14 MR on 95% of tested samples. The QXDx™ BCR-ABL %IS assay demonstrated excellent correlation with the comparator test using a Weighted Deming regression with a Pearson R correlation coefficient of 0.99, slope 1.037 and intercept of 0.1084. College of American Pathologists(CAP) challenges (n=6) were conducted from 2016-2019, QXDx™ BCR-ABL %IS system results were regressed vs the mean values published by CAP yielded a slope of 1 and R2=0.99. Conclusions: The QXDx™ BCR-ABL %IS Kit on the QXDx™ AutoDG™ Droplet Digital PCR System can be used safely and effectively in the laboratory on t(9;22) positive CML patients for monitoring of treatment with Tyrosine Kinase Inhibitors (TKIs). Citation Format: Dawne N. Shelton, Prasanthi Bhagavatula, Nathan Sepulveda, Lan Beppu, Jerald Radich. Performance characteristics of the first FDA-cleared droplet digital PCR (ddPCR) IVD assay for monitoring chronic myelogenous leukemia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6483.

Derivation of Passing-Bablok regression from Kendall's tau.

It is shown how Passing's and Bablok's robust regression method may be derived from the condition that Kendall's correlation coefficient tau shall vanish upon a scaling and rotation of the data. If the ratio of the standard deviations of the regressands is known, a similar procedure leads to a robust alternative to Deming regression, which is known as the circular median of the doubled slope angle in the field of directional statistics. The derivation of the regression estimates from Kendall's correlation coefficient makes it possible to give analytical estimates of the variances of the slope, intercept, and of the bias at medical decision point, which have not been available to date. Furthermore, it is shown that using Knight's algorithm for the calculation of Kendall's tau makes it possible to calculate the Passing-Bablok estimator in quasi-linear time. This makes it possible to calculate this estimator rapidly even for very large data sets. Examples with data from clinical medicine are also provided.

Determination of anabolic steroids in dried blood using microsampling and gas chromatography-tandem mass spectrometry: Application to a testosterone gel administration study.

Anabolic androgenic steroids (AAS) have been the most commonly abused substances taken by not only professional sportsmen but also recreational bodybuilders. The detection of micro-dose testosterone (T) misuse is particularly challenging as it possesses pseudo-endogenous origin and is sometimes impossible to be identified in urine samples. Dried blood (DB) obtained by finger pricking has been proven to be an alternative matrix for better correlating to physiological responses. Moreover, the introduction of the volumetric absorptive microsampling (VAMS) technology allows overcoming some major limitations of spotting blood onto a filter paper card. In this work, a fast and sensitive GC-MS/MS method was developed and validated for the quantification of AAS in DB collected by means of VAMS. T and the eight top abused synthetic AAS, namely nandrolone, boldenone, mesterolone, drostanolone, metenolone, metandienone, oxandrolone, and dehydrochloromethyl T were selected as the target analytes. The method based on VAMS exhibited good precision, accuracy as well as stability, and superior extraction recoveries over the punched DB spots reported in the literature. The chromatographic separation was achieved within 6.4 min and the detection limit is as little as 50 fg (i.e. able to detect 0.10 ng mL-1 in 20 μL of DB). Confirmed by forty real blood samples, the Deming regression and Bland-Altman analysis revealed that the VAMS DB could be employed for quantifying blood T level in agreement with using the serum specimen. The feasibility of the method was then successfully proven by the analysis of samples collected from a three-arm T administration trial. Our results highlighted that DB total T was a sensitive indicator for identifying transdermal micro-dosing of T. In the groups of receiving T gel administration, T concentrations could rise up to ten times higher than the baseline at 9 h after the application. As a future step, this approach is being expanded to a large cohort screening of bodybuilders at gym and ultimately may allow universal applications on monitoring sports drug misuse.

Comparison between Hyperspectral Imaging and Chemical Analysis of Polyphenol Oxidase Activity on Fresh-Cut Apple Slices

The assessment of the quality of fresh-cut apple slices is important for processing, storage, market value, and consumption. Determination of polyphenol oxidase activity (PPO) in apples is critical for controlling the quality of the final product (i.e., dried apples and juices). Hyperspectral imaging (HSI) is a nondestructive, noncontact, and rapid food quality assessment technique. It has the potential to detect physical and chemical quality attributes of foods such as PPO of apple. The aim of this study was to investigate the suitability of HSI in the visible and near-infrared (VIS-NIR) range for indirect assessment of PPO activity of fresh-cut apple slices. Apple slices of two cultivars (cv. Golden Delicious and Elstar) were used to build a robust detection algorithm, which is independent of cultivars and applied treatments. Partial least squares (PLS) regression using the 7-fold cross-validation method and method comparison analysis (Bland–Altman plot, Passing–Bablok regression, and Deming regression) were performed. The 95% confidence interval (CI) bands for the Bland–Altman analysis between the methods were −4.19 and 13.11, and the mean difference was 3.7e−12. The Passing–Bablok regression had a slope of 0.8 and an intercept of 7.6. The slope of the Deming regression was 0.8 within the CI bands of 0.56 and 1.10. These results show acceptable performance and no significant deviation from linearity. Hence, the results demonstrated the feasibility of HSI as an indirect alternative to the standard chemical analysis of PPO enzyme activity.

Clinical Validation of a Dried Blood Spot Assay for 8 Antihypertensive Drugs and 4 Active Metabolites.

Drug nonadherence is one of the major challenges faced by resistant hypertension patients, and identification of this problem is needed for optimizing pharmacotherapy. Dried blood spot (DBS) sampling is a minimally invasive method designed to detect and determine the degree of nonadherence. In this study, a DBS method for qualifying 8 antihypertensive drugs (AHDs) and 4 active metabolites was developed and validated using ultra high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The DBS assay was validated analytically and clinically, in accordance with FDA requirements. Analytical validation was accomplished using UHPLC-MS/MS. For clinical validation, paired peak and trough levels of DBS and plasma samples were simultaneously collected and comparatively analyzed using Deming regression and Bland-Altman analyses. All concentrations below the set lower limit were excluded. Deming regression analysis was used to predict comparison bias between the collected plasma and DBS samples, with DBS concentrations corrected accordingly. The UHPLC-MS/MS method for simultaneously measuring 8 AHDs and their metabolites in DBS, was successfully validated. With Deming regression no bias was observed in N = 1; constant bias was seen in N = 6 and proportional bias in N = 11 of the AHDs and metabolites. After correction for bias, only one metabolite (canrenone) met the 20% acceptance limit for quantification, after Bland-Altman analyses. In addition, amlodipine, valsartan, and [enalaprilate] met the 25% acceptance limit. A novel DBS assay for simultaneously qualifying and quantifying 8 AHDs and their metabolites, has been successfully developed and validated. The DBS assay is therefore a suitable method to detect drug nonadherence. However, with the exception of canrenone, the interchangeable use of plasma and DBS sampling to interpret drug quantities should be avoided.

Thermal tolerances and species interactions determine the elevational distributions of insects

AbstractAimPhysiological limits to thermal extremes are often thought to determine the abundance and geographical distribution of species, but more recent evidence suggests that species interactions might be equally important. Moreover, the relative importance of these constraints might shift with changing abiotic conditions, such as climate change. Here, we explore the relative importance of physiological tolerances to heat and species interactions in determining the distribution of insects along two elevational gradients. The gradients contrast in precipitation but not temperature, allowing us to separate these two climatic factors.LocationMontane rainforest in Costa Rica.Time period2015–2016.Major taxa studiedBromeliad‐dwelling aquatic insect larvae.MethodsWe estimated the elevational preferences of five insect taxa by surveying 170 bromeliads along the moist Atlantic and the dry Pacific slopes of Monteverde and determined their critical thermal maxima (CTmax) experimentally. We determined whether taxon‐specific heat tolerances predicted their elevational preferences, using Deming regressions, and tested whether potential predators mediated effects on the elevation of insect distributions, using structural equation models.ResultsOn the moist Atlantic slope, heat tolerances of insects explained their elevational distributions: taxa with high heat tolerances preferred low elevations where conditions were warmest, whereas taxa with low heat tolerances preferred high elevations where conditions were coldest. In contrast, on the drier Pacific slope, the elevational abundance pattern of many insects reflected negative interactions from crane fly larvae. These larvae are known to become predatory in drought conditions and were disproportionally abundant at low elevations on the Pacific slope.Main conclusionsWe show that under drought, indirect effects mediated by species interactions can override any direct physiological effects of environmental conditions on insect distributions. The relative importance of limits to physiological tolerance and species interactions thus depends on the environmental context, an important insight given that environmental conditions are expected to shift with climate change.

Shortcoming of Visual Interpretation of Cardiotocography: A Comparative Study with Automated Method and Established Guideline Using Statistical Analysis

Cardiotocography (CTG) has been the primary tool for monitoring the fetal health during antepartum and intra-partum period since the 1960s. It works by recording both fetal heart rate and mother’s uterine contraction pressure simultaneously. However, due to lack of consensus in the interpretation of features and due to inter- and intra-clinician variation the introduction of CTG in fetal care did little to reduce the fetal mortality and morbidity. In order to ensure that the signs of hypoxia are recognised at the onset it is necessary to have a robust clinical decision support system. Visual analysis by clinicians has been known to produce erroneous result as it is not possible to detect subtle changes with naked eye. Though many guidelines have been proposed, NICHD guidelines for the analysis of CTG are the widely acceptable one. In this work, authors compared inter- and intra-clinician variation using statistical measures and found poor agreement between them. Parameters of CTG were compared using fuzzy-logic-based algorithms developed by authors and the algorithm based on NICHD guidelines. Kappa coefficient, Bland–Altman and Deming regression showed that there was a good agreement between the two methods in measuring both quantitative parameters and qualitative parameters. For the overall classification of CTG, majority voting showed the disagreement between the clinicians. There was a good agreement between the three methods in identifying Normal CTG, but the agreement was poor for Pathological CTG when visual interpretation was compared with the other two methods using Deming regression, sensitivity and specificity analysis and Bland–Altman plot. The analyses established that visual interpretation fails to perform well when compared to the automated procedure and the guidelines of NICHD. Among the three methods, the automated system performed better as it had high true positive (TP) and true negative (TN) values while identifying Pathological CTGs.

Quality of blood samples collected at home does not affect clinical decision making for the administration of systemic cancer treatment

The aim of this exploratory clinical study was to evaluate whether the preanalytical quality of blood samples subjected to delayed centrifugation and transport – as a result of home-sampling – is affected in a way it alters the clinical decision-making for patients under systemic cancer therapy. This evaluation is part of a comprehensive investigation of the opportunities for oncological home-hospitalization. Forty-nine patients with cancer donated two additional blood samples during their ambulatory hospital visit. Fifteen blood analytes were compared between routine blood samples and samples that were subjected to transport and delayed centrifugation in order to mimic a locally implemented model for oncological home-hospitalisation. Deviations were analysed by means of Deming regression. For those analytes showing statistically significant intercepts and/or slopes, the mean deviations were compared to the desirable analytical bias; and the intra-individual differences were compared with the limits for clinical decision-making. Statistically significant intercepts and/or slopes were observed for haematocrit (HCT), mean cellular volume (MCV), platelets count (PLT) and C-reactive protein (CRP). Differences exceeding the allowable margins of desirable analytical bias were observed for HCT and MCV. Risk of different clinical decision-making couldn’t be observed for any of the analytes showing statistically significant differences. These results demonstrate that home-collection of blood samples, transported at room temperature and centrifuged within a mean time of five hours after sampling, has no effect on clinical decision-making with regards to systemic cancer therapy. However, attention should be paid to the potential occurrence of haemolysis during the preanalytical phase, which can negatively influence haemolysis-dependent variables.

Reliability of a New Test of Balance Function in Healthy and Concussion Populations.

Providing quantitative measures of balance and posture is a valuable aid in clinical assessment and in recent years several devices have been introduced that have demonstrated the accurate measure of balance via deviation of center of mass utilizing software algorithms and mobile devices. The purpose of this study was to assess the accuracy of EQ Balance against the SwayTM Balance System (Sway), another balance device that is currently established as an accurate measure of balance, and to evaluate the test–retest reliability of EQ Balance. Seventy individuals presenting to a sports medicine and concussion clinic volunteered to participate in the assessment of balance utilizing Sway and EQ Balance simultaneously. The group included 25 males and 45 females (mean age: 37.8 ± 14.8, range: 13–65) with and without concussion or other neurological conditions (39 concussed vs. 31 non-neurologically injured, or healthy). Twenty-six of the concussed participants were balance-impaired. Participants performed five postures while holding the mobile device against their chest. Participants held a device holder that secured two devices: one iPhone 6 with EQ Balance and a second iPhone 6 with Sway Balance. The average balance score on all five stances was recorded as the “average balance score”. Average balance scores were in statistical agreement between the two methods across the entire group, and for sub-groups according to the Deming regression (p < 0.01). The intra-class correlation (ICC) for the cohort was 0.87 (p < 0.001). Across the cohort, EQ Balance measured significantly worse balance scores in the balance-impaired group, comprised of participants with brain injury who failed a clinical balance screening test, compared to the group without clinically-determined balance impairment (this group includes healthy and some concussed patients). EQ Balance demonstrated safety, as it was considered safe to perform independently (i.e., without an observer) in those with impaired balance, and high test- retest reliability in the healthy and concussed patient population. Statistical agreement was established between the two measures of EQ Balance and Sway Balance for the average balance score across all five stances. The ICC analysis demonstrates strong consistency of the task output between test sessions. Given these results, EQ Balance demonstrates strength as a new balance assessment tool to accurately measure balance performance as part of a unique and novel gamified application in healthy and neurologically injured populations.