Mean Coefficient Of Variation Values Research Articles

Test-retest reliability and agreement of remote home-based functional capacity self-administered assessments in community-dwelling, socially isolated older adults.

To determine the test-retest reliability and agreement of home-based functional capacity self-administered assessments in socially isolated older adults. Fourteen community-dwelling older adults (eight females, 67.9 ± 7.7 years) volunteered for this study. Before testing, participants were screened online for eligibility and received instructional videos explaining test set-up and execution. Participants underwent the 30-second sit-to-standing test, gait speed tests at the usual pace, and timed-up-and-go tests administered 4 weeks apart. For the 30-second sit-to-standing protocol, participants were instructed to repeatedly sit and stand from a chair (with a height of ∼ 43 cm and without armrests) for 30 s, with the number of repetitions recorded. In the gait speed test protocol, participants were instructed to walk at their usual and comfortable pace, with the time taken recorded (seconds). In the timed-up-and-go, participants stood up from a chair, walked as fast as possible for 3 m, circled a marked point, and returned to the chair to sit down, completing the test, with the score recorded (seconds). A trained researcher conducted the scoring virtually via synchronous video. 30-second sit-to-standing, gait speed test, and timed-up-and-go showed excellent mean coefficient of variation values (2.0-4.9), small standard error of measurement (0.08-1.27), excellent intraclass coefficient (0.97-0.99), very strong correlations (0.97-0.99) and good agreement between the two days of testing. Self-administered functional capacity tests performed by older adults at home were reliable with good agreement. Healthcare professionals and older adults should take advantage of simple remote self-administered assessments performed at home to evaluate older adults' health status.

An evaluation of corneal endothelial cell morphology in patients with thyroid-associated ophthalmopathy.

To evaluate corneal endothelial cell morphology in patients with thyroid-associated ophthalmopathy (TAO). Seventy-two eyes of 36 patients with TAO presenting to the ophthalmology department between January 2018 and January 2022 were included in the study. The findings were compared with 98 eyes of 49 healthy individuals. Mean endothelial cell density (ECD), coefficient of variation (CV), maximum cell area, minimum cell area, average cell area, and hexagonality ratio were obtained using non-contact specular microscopy. The thicknesses of peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC) were measured using optical coherence tomography (OCT). The TAO group consisted of 36 patients, 11 (30.6%) men and 25 (69.4%) women, and the control group of 49 healthy individuals, 14 (28.6%) men and 35 (71.4%). No significant differences were determined between the TAO and control groups in terms of the specular microscopy findings of mean ECD, CV, or hexagonality ratio values (p > 0,05). However, the mean Hertel values differed significantly between the two groups (p = 0.001). When the TAO group was divided into two subgroups based on patients who had previously received prednisolone therapy and those who had not, significant differences were observed in terms of mean ECD, CV, and hexagonality ratio values (p > 0.05). Comparison of patients diagnosed with active TAO and receiving prednisolone therapy and the TAO patients with inactive disease revealed lower ECD, higher CV values, and lower hexagonality ratios in the prednisolone therapy group. These findings all suggest that inflammation in patients undergoing active disease affects the corneal endothelium.

Challenges in fish aging: the role of otolith preparation technique and experience level in aging lake whitefish (Coregonus clupeaformis)

Lake whitefish ( Coregonus clupeaformis (Mitchill, 1818)) is an important commercial and recreational species in the Great Lakes. Precise age estimates are important for management, and two widely used techniques for otolith preparation are thin-section and crack-and-burn, which have not been compared for lake whitefish. Sagittal otoliths were collected from 92 lake whitefish in Green Bay and Lake Michigan and aged using thin-section and crack-and-burn techniques. Otoliths were aged independently by three individuals (two novices and one expert) to assess repeatability in estimated ages. Our investigation highlights the inherent difficulty of aging lake whitefish, where thin-section produced significantly older estimated ages (6–30 years) compared to crack-and-burn (5–26 years). Percent agreement of estimated ages between preparation techniques was low for all readers within ±0 years but increased when tolerance buffers were applied. Mean coefficient of variation values from both experience levels (>10.8%) exceeded the acceptable range reported in the literature (5%–7%); however, species longevity and nature of the structure must be considered when establishing target values. Variation in estimated ages is attributed to the experience level and interpretation of structural features. Species-specific training and establishing an objective framework to identify annuli will improve precision metrics.

Development of a droplet digital PCR assay to detect illicit glucocorticoid administration in bovine.

Glucocorticoids are often used illegally in food-producing animals for the growth promotion of livestock animals. In accordance to official chemical methods for glucocorticoid detection, an animal is declared as non-compliant when a residue is identified in the sample. Neverthless, growth promoting molecules can often escape identification due to their rapid elimination or due to the use of non-detectable new generation drugs. Therefore, an indirect screening method able to detect the biological effect of long-term administration of low doses of dexamethasone and prednisolone on livestock has been developed to support official methods. As already described, FKBP5 (FKBP prolyl isomerase 5) expression in bovine thymus is regulated by glucocorticoids, and this specific regulation can be exploited in an indirect screening assay. In the present study, male veal calves and young bulls were considered in three different trials in which estradiol, dexamethasone, and prednisolone were administered alone or in combination with Revalor-200 subcutaneous pellets. Thoracic thymus was sampled from all animals and molecular analysis was performed. A duplex droplet digital PCR assay with EvaGreen® was employed to detect the target gene expression using absolute quantification. The developed droplet digital PCR assay was precise, showing intra- and inter-assay mean coefficient of variation values of about 6.16% and 3.17%, respectively. It was also highly specific (100%) with Youden’s index of 76.92% and 53.57% applied to veal calves and young bulls, respectively. The lowest detection limit in which the target gene expression level was kept constant, was 0.05 ng/μl of cDNA with 1 copies/μL and 0.5 copies/μL for target and reference gene, respectively. This study establishes the basis for using a digital PCR-based assay as an efficient test to identify animals illegally treated with glucocorticoids.

Open-source image analysis software yields reproducible MRI measures of lumbar intervertebral disc degeneration in sheep models.

Sheep are established models for intervertebral disc degeneration (IVDD) translational research. Objectives of this retrospective, secondary analysis, observational study were to evaluate reproducibility of two magnetic resonance imaging (MRI) measures of IVDD in sheep using open-source image analysis software. Sagittal planar, T2-weighted, lumbar MRI scans from a previous, prospective study were evaluated (4 sheep @ 3 treatment periods/sheep @ 7 lumbar discs /treatment period=84 discs). A standardized protocol was developed for measuring MRI index (nucleus pulposus signal intensity × nucleus pulposus sagittal area), and nucleus pulposus signal intensity standard deviation (NPSISD). Scans were randomized and four observers with varying experience levels applied the protocol to independently perform triplicate measures. Mean coefficient of variation values for both the MRI index and NPSISD were within an acceptable range (<10). Mean values for the three readers with at least 2 months of image analysis experience did not differ (P>.05).

Implications of intra-plot heterogeneity for yield estimation accuracy: Evidence from smallholder maize systems in Ethiopia.

Intra-plot heterogeneity in yield is often observed in smallholder farming systems, although its implications for yield measurement remain under-investigated. Using a unique dataset on smallholder maize production in Ethiopia, we quantify the magnitude of inter- and intra-plot heterogeneity, describe the relationship between intra-plot heterogeneity and maize productivity, and document the implications of intra-field heterogeneity on the accuracy of alternative yield estimation protocols. Our data include five common yield estimation protocols, as well as full plot harvests of 230 smallholder maize fields. We surveyed agronomic decisions, biophysical variables, and accessibility characteristics of the surveyed fields. We quantify intra-plot heterogeneity using the coefficient of variation (CV) of stand density, cob weight, and maize grain yield. A generalized linear mixed model is used to explore the relationship between these variables and the method- and heterogeneity-dependence of yield estimation accuracy. We find inter-plot CV values ranging from 32 to 56 %, 22 to 73 % and 39 to 49 % in population density, cob weight and grain yield, respectively. Intra-plot heterogeneity constituted most of this variation, with across-method mean CV values of 41 %, 82 % and 63 %, respectively, of the total variability in population density, cob weight and grain yield. A rise in intra-plot heterogeneity of 0.5 % to 0.8 % is associated with a significant increase in yield estimation error under alternative yield estimation protocols. Regression analysis shows that interactions in agronomic decisions, input intensity and plot accessibility factors dictate intra-plot heterogeneity and method accuracy in smallholder systems. Intra-plot heterogeneity is larger than inter-plot heterogeneity in the current study area. Our analysis shows that the effect of intra-plot heterogeneity on yield estimation accuracies is method-dependent and yield estimation methods that fail to capture true intra-plot heterogeneity are more error-prone. Results of such estimations should be considered with caution when used as the basis of decision-making.

Cerebral hemodynamics in peritoneal dialysis versus intermittent hemodialysis: A transcranial Doppler pilot study.

This study evaluated intradialytic cerebral hemodynamics measured by transcranial Doppler (TCD) in intermittent hemodialysis (iHD) versus nightly peritoneal dialysis (NIPD). Intradialytic TCD was serially performed in chronic dialysis patients receiving iHD (n = 10) and NIPD (n = 10). A linear mixed model was used to model mean flow velocity (MFV), pulsatility index (PI), and mean arterial pressure (MAP) as functions of time and treatment group. Intradialytic cerebral volatility (IDCV) was calculated using the coefficient of variation (CV) and mean absolute value of change (AVC) of each patient's MFV, PI, and MAP values over time. Mixed model analyses found no significant difference between MFV, PI, and MAP treatment groups in change over time, though volatility differed significantly. Mean CV values for MFV, PI, and MAP were higher in iHD than NIPD (MFV 0.22 vs. 0.10, p = 0.005; PI 0.14 vs. 0.08, p = 0.003; MAP 0.057 vs. 0.032, p = 0.009). AVC values were similarly higher in iHD compared to NIPD (MFV 8.26 vs. 4.43, p = 0.04; PI 0.17 vs. 0.084, p < 0.001; MAP 6.05 vs. 2.9, p = 0.003). PI, MFV, and MAP were more stable in NIPD than iHD, as measured by intradialytic TCD monitoring. This study identifies IDCV as a unique TCD metric for intradialytic cerebral hemodynamics.

Comparison of Sectioned and Whole Otoliths for Estimating Bluegill Age

Abstract Three readers independently assigned ages to 257 paired sectioned and whole Bluegill Lepomis macrochirus otoliths to examine between-reader precision of age estimates and to compare estimates obtained using the two otolith preparation methods. Percent exact between-reader agreement varied from 93.4% to 96.9% for sectioned otoliths and 92.2% to 94.2% for whole otoliths. Mean coefficient of variation values for between-reader comparisons were &amp;lt; 5.0% for all reader combinations and both otolith preparation methods. Exact agreement between paired whole and sectioned otoliths varied by reader from 82.8% to 85.2%; whereas coefficient of variation values ranged from 7.8% to 8.9%. The only significant departure from a 1:1 relationship for mean age estimates between the two preparation methods occurred for young fish in the estimates of one reader. This bias was not pervasive, as no significant bias was indicated in older fish. Our results suggest that age estimates obtained from sectioned and whole Bluegill otoliths are precise and the time and associated expense of mounting and sectioning Bluegill otoliths may not be necessary as whole otolith ages were generally concordant with sectioned ages to age 8 y.

Corneal thickness and endothelial changes in long-term hydroxychloroquine use

Objective: To determine possible associations between long-term HCQ use and corneal changes in patients who used HCQ for at least 3 years.Materials and methods: The study included 62 healthy controls and 62 consecutive patients who used HCQ for the treatment of rheumatologic disease and were referred to the ophthalmology department between August 2018 and November 2018 for HCQ retinal toxicity screening. Central corneal thickness (CCT), corneal endothelial cell density (ECD), the coefficient of variation (CV) of cell size, and the percentage of hexagonal cells (HEX%) were measured to evaluate changes in the cornea.Results: The mean age of the patient group and control group was 50.10 ± 10.91 and 50.53 ± 10.67 years, respectively. The mean ECD was 2742 ± 347 (cells/mm2) in the patient group and 2875 ± 188 cells/mm2 in the control group. There was a significant difference between groups (p = 0.01). The mean CCT was 567.05 ± 32.35 µm in the patient group and 540.15 ± 38.50 µm in the control group. CCT was significantly higher in the patient group compared with control group (p < 0.001). There was no significant difference between groups in terms of mean CV and HEX values (p > 0.05).Conclusions: Patients using long-term HCQ demonstrated lower ECD and higher CCT than the control group. However, the CV of cell sizes and the HEX % values were not significantly different from the controls.

Reproducibility and reliability of retinal and optic disc measurements obtained with swept-source optical coherence tomography in a healthy population.

To analyze the reproducibility of macular and peripapillary thickness measurements, and optic nerve morphometric data obtained with Triton Optical coherence tomography (OCT) in a healthy population. Observational cross sectional study. A total of 108 eyes underwent evaluation using the Triton Swept Source-OCT. A wide protocol was used and measurements in each eye were repeated three times. Morphometric data of the optic nerve head, full macular thickness, ganglion cell layer (GCL) and retinal nerve fiber layer thickness (RNFL) were analyzed. For each parameter, the coefficient of variation (COV) and the intra-class (ICC) correlation values were calculated. Measurements were highly reproducible for all morphometric measurements of the optic disc, with a mean COV of 6.36%. Macular full thickness showed good COV and ICC coefficients, with a mean COV value of 1.00%. Macular GCL thickness showed a mean COV value of 3.06%, and ICC higher than 0.787. Peripapillary RNFL thickness showed good COV and ICC coefficients, with a mean COV value of 8.31% and ICC higher than 0.684. The inferotemporal sector showed the lowest ICC (0.685). Triton OCT presents good reproducibility values in measurements corresponding to retinal parameters, with macular measurements showing the highest reproducibility rates. Peripapillary RNFL measurements should be evaluated with caution.

Assessing the inter-annual variability of separation distances around odour sources to protect the residents from odour annoyance

In recent years, there has been a growing concern about potential impacts on public health and wellbeing due to exposure to environmental odour. Separation distances between odour-emitting sources and residential areas can be calculated using dispersion models, as a means of protecting the neighbourhood from odour annoyance. This study investigates the suitability of using one single year of meteorological input data to calculate reliable direction-dependent separation distances. Accordingly, we assessed and quantified the inter-annual variability of separation distances at two sites with different meteorological conditions, one in Brazil and the other in Austria. A 5-year dataset of hourly meteorological observations was used for each site. Two odour impact criteria set in current regulations were selected to explore their effect on the separation distances. The coefficient of variation was used as a statistical measure to characterise the amount of annual variation. Overall, for all scenarios, the separation distances had a low degree of inter-annual variability (mean coefficient of variation values from 8% to 21%). Reasonable agreements from year to year were therefore observed at the two sites under investigation, showing that one year of meteorological data is a good compromise to achieve reliable accuracy. This finding can provide a more cost-effective solution to calculate separation distances in the vicinity of odour sources.

Coefficient of variation on Gd-EOB MR imaging: Correlation with the presence of early-stage hepatocellular carcinoma in patients with chronic hepatitis B

PurposeTo study whether the measurement of hepatic fibrosis on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) magnetic resonance (MR) imaging using the coefficient of variation (CV) might be correlated with the presence of hepatocellular carcinoma (HCC) in patients with chronic hepatitis B (CHB). Materials and methodsThis study included 104 patients with and without CHB, who were divided into 4 groups: control group, CHB without liver cirrhosis (LC; Group I), CHB with LC (Group II), and CHB with LC and HCC (Group III). MR images were analyzed to measure the inhomogeneity of signal intensities calculated using the CV map of the liver parenchyma. Intergroup comparisons of CV values were performed using ANOVA. The diagnostic performance of the CV map and alpha-fetoprotein (AFP) for diagnosing HCC was evaluated using the receiver operating characteristic (ROC) curve. ResultsOn the hepatobiliary phase of Gd-EOB-DTPA-enhanced T1-weighted imaging, the mean CV values of the control group and Groups I, II, and III were 3.9 ± 0.99, 3.97 ± 1.09, 5.58 ± 2.05, and 6.80 ± 2.34, respectively (P = 0.000). On ROC analysis of the CV value for predicting HCC, the value of the area under the curve (AUC) on Gd-EOB-DTPA MR imaging was 0.788 (95% CI: 0.697-0.862). The sensitivity and specificity were 84.2% and 63.6%, respectively, at a CV cutoff value >4.75. The value of AUC determined using AFP was 0.766. ConclusionThe CV value for hepatic fibrosis on Gd-EOB-DTPA MR imaging may be correlated with the presence of HCC in patients with CHB, and shows comparable diagnostic performance to AFP analysis.

Corneal endothelial changes in patients with vitamin D deficiency.

Purpose:The purpose of this study is to evaluate the effect of vitamin D deficiency on corneal endothelial layer using specular microscopy.Methods:Fifty-eight eyes of 58 patients whose vitamin D level was below 15 ng/ml and who had no ocular pathology were included in the study (Group 1). Forty eyes of 40 age-and sex-matched subjects were enrolled as control group (Group 2). Corneal endothelial cell density (CD), coefficient of variation (CV), hexagonal cell ratio (HEX), and central corneal thickness (CCT) were measured using specular microscopy (Konan Medical Inc., Nishinomiya, Japan). The obtained data were compared between the groups.Results:There was no significant difference between the groups in terms of age and gender (P = 0.344, P = 0.399, respectively). The mean CD value was 2772.79 ± 202.21 cells/mm2 in Group 1 and 2954.97 ± 116.89 cells/mm2 in Group 2 (P = 0.001). The mean CV value was 30.31 ± 3.65 in Group 1 and 28.20 ± 2.71 in Group 2 (P = 0.003). The mean HEX value was 46.56 ± 6.32 in Group 1 and 51.07 ± 5.28 in Group 2 (P = 0.001). The mean CCT value was 555.87 ± 36.90 μ in group 1 and 549.0 ± 37.39 μ in Group 2 (P = 0.96).Conclusion:Vitamin D deficiency may affect the corneal endothelial layer. Patients with vitamin D deficiency should be evaluated for endothelial parameters in particular before an intraocular surgery. Further studies are needed to confirm our results.

Detection and molecular characterisation of a diagnosis escape variant associated with occult hepatitis B virus in Brazil.

BACKGROUND Many studies have identified mutations in the hepatitis B surface antigen (HBsAg) as important factors limiting the ability of commercial serological assays to detect this viral antigen. However, an association between mutations in the HBsAg gene and the occurrence of occult HBV infection (OBI) in patients has not been established.OBJECTIVES To detect hepatitis B virus (HBV) DNA in patients with anti-HBc as a unique serological marker, a previously published, cost-effective TaqMan-based real-time polymerase chain reaction (PCR) test with minor groove binding probes was adapted for use in this study. The current study also aimed to investigate HBsAg mutations and genotypes of HBV in OBI at the Viral Hepatitis Ambulatory Clinic in Rio de Janeiro to determine any possible association.METHODS Intra-assay and inter-assay reproducibility were determined, and the mean coefficient of variation values obtained were 2.07 and 3.5, respectively. Probit analysis indicated that the 95% detection level was 25 IU/mL. The prevalence of OBI was investigated in 35 serum samples with an ‘anti-HBc alone’ profile from individuals who attended our clinic between 2011 and 2013.FINDINGS HBV DNA was detected in only one sample, resulting in an OBI rate of 2.9%. Nucleotide sequencing of the pre-S/S region was performed to genotype and analyse mutations within the HBsAg gene of this HBV DNA. The HBV in the OBI case was classified as sub-genotype A1, and a sequence analysis of the small S gene revealed 12 mutations in the major hydrophilic region compared to the consensus A1 sequence. Most of these mutations occurred in amino acid residues that have been reported as clinically relevant because they have been implicated in vaccine escape and/or inability to detect HBsAg by commercial serological assays.MAIN CONCLUSIONS Our study suggests the importance of specific HBsAg mutations, different from those in D, B, and C genotypes, in sub-genotype A1 HBV associated with OBI.

Corneal endothelial changes in long-term cannabinoid users

Purpose: The aim of this study was at evaluating the effects of long-term cannabis use on the corneal endothelial cells with the specular microscopy.Methods: The study enrolled 28 eyes of 28 patients diagnosed with cannabinoid use disorder. The cannabinoid group was selected among patients who had been using the substance for three days or more per week over the past one year. Thirty-two eyes of 32 age- and sex-matched healthy individuals enrolled as control group in the study. Corneal endothelial cell density (CD), coefficient of variation (CV) and hexagonal cell ratio (HEX) values were analyzed by specular microscopy.Results: The mean CD was 2900 ± 211 cells/mm2 in the cannabinoid group and 3097 ± 214 cells/mm2 in the control group (p < 0.01). There was a significant decrease in cannabinoid group. The mean CV was 29 ± 7 and 27 ± 4 in the cannabinoid and control groups, respectively (p > 0.05). No significant difference was present between the cannabinoid and the control groups in terms of mean CV value. The mean HEX was 52 ± 5% in the cannabinoid group and 53 ± 10% in the control group (p > 0.05). There was not a significant difference between the cannabinoid and the control groups in terms of mean HEX value.Conclusion: A significant decrease in CD was found in cannabinoid users compared the control group.

Quantitative Measurement of Hepatic Fibrosis with Gadoxetic Acid-Enhanced Magnetic Resonance Imaging in Patients with Chronic Hepatitis B Infection: A Comparative Study on Aspartate Aminotransferase to Platelet Ratio Index and Fibrosis-4 Index.

ObjectiveTo quantitatively measure hepatic fibrosis on gadoxetic acid-enhanced magnetic resonance (MR) in chronic hepatitis B (CHB) patients and identify the correlations with aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 index (FIB-4) values.Materials and MethodsThis study on gadoxetic acid-enhanced 3T MR imaging included 81 patients with CHB infection. To quantitatively measure hepatic fibrosis, MR images were analyzed with an aim to identify inhomogeneous signal intensities calculated from a coefficient of variation (CV) map in the liver parenchyma. We also carried out a comparative analysis between APRI and FIB-4 based on metaregression results. The diagnostic performance of the CV map was evaluated using a receiver-operating characteristic (ROC) curve.ResultsIn the MR images, the mean CV values in control, groups I, II, and III based on APRI were 4.08 ± 0.92, 4.24 ± 0.80, 5.64 ± 1.11, and 5.73 ± 1.28, respectively (p < 0.001). In CHB patients grouped by FIB-4, the mean CV values of groups A, B, and C were 4.22 ± 0.95, 5.40 ± 1.19, and 5.71 ± 1.17, respectively (p < 0.001). The mean CV values correlated well with APRI (r = 0.392, p < 0.001) and FIB-4 (r = 0.294, p < 0.001). In significant fibrosis group, ROC curve analysis yielded an area under the curve of 0.875 using APRI and 0.831 using FIB-4 in HB, respectively.ConclusionGadoxetic acid-enhanced MR imaging for calculating a CV map showed moderate correlation with APRI and FIB-4 values and could be employed to quantitatively measure hepatic fibrosis in patients with CHB.

An Inter-Laboratory Comparison for the Urinary Acrolein Biomarker 3-Hydroxypropyl-Mercapturic Acid (3-HPMA)

Summary An inter-laboratory comparison study on the acrolein biomarker of exposure 3-hydroxypropyl-mercapturic acid (3-HPMA) with 12 laboratories from 7 globally distributed countries was performed. The laboratories received coded triplicates of 4 spiked and lyophilized urine samples (LU, 12 samples) as well as 5 authentic urine pool samples (PU, 15 samples) covering the 3-HPMA concentration range from background (non-smoking) to heavy smoking levels for analysis by using their own (in-house) analytical method. All laboratories applied liquid chromatography with tandem mass spectrometry (LC-MS/MS), with most of them (10 of 12) using solid phase extraction (SPE) as sample work-up procedure. The intra-laboratory variation (indicating repeatability) was determined by calculating the standard deviation (sr) and the coefficient of variation (CVr) of the triplicates, whereas the inter-laboratory variation (indicating reproducibility) was determined by calculating the standard deviation between laboratories (sR) and the corresponding coefficient of variation (CVR). After removal of outlier samples or laboratories, the mean CVr values for LU and PU test samples ranged from 2.1–3.6% (mean: 2.8%) and 2.4–3.7% (mean: 3.3%), respectively, indicating good repeatability for the determination of 3-HPMA in both sample types. CVR for LU and PU test samples ranged from 9.1–31.9% (mean: 18.8%) and 13.9–27.0% (mean: 18.5%), respectively, indicating limited reproducibility in 3-HPMA analysis for both sample types. Re-calculation of the PU results by applying an embedded calibration (EC), derived from the reported peak areas for the LU test samples, somewhat improved the CVR values (range: 9.6–28.8%, mean: 16.7%). It is concluded that the intra-laboratory variation (repeatability) in the determination of 3-HPMA in urine is in general acceptable in the participating laboratories, while the inter-laboratory variability requires further improvement. The relatively small reduction in the inter-laboratory variability (sR and CVR) by applying an EC suggests that other methodological factors than the standard reference material for 3-HPMA have to be addressed to achieve further improvement in reproducibility.

Editors’ Note

Summary An inter-laboratory comparison study on the acrolein biomarker of exposure 3-hydroxypropyl-mercapturic acid (3-HPMA) with 12 laboratories from 7 globally distributed countries was performed. The laboratories received coded triplicates of 4 spiked and lyophilized urine samples (LU, 12 samples) as well as 5 authentic urine pool samples (PU, 15 samples) covering the 3-HPMA concentration range from background (non-smoking) to heavy smoking levels for analysis by using their own (in-house) analytical method. All laboratories applied liquid chromatography with tandem mass spectrometry (LC-MS/MS), with most of them (10 of 12) using solid phase extraction (SPE) as sample work-up procedure. The intra-laboratory variation (indicating repeatability) was determined by calculating the standard deviation (sr) and the coefficient of variation (CVr) of the triplicates, whereas the inter-laboratory variation (indicating reproducibility) was determined by calculating the standard deviation between laboratories (sR) and the corresponding coefficient of variation (CVR). After removal of outlier samples or laboratories, the mean CVr values for LU and PU test samples ranged from 2.1–3.6% (mean: 2.8%) and 2.4–3.7% (mean: 3.3%), respectively, indicating good repeatability for the determination of 3-HPMA in both sample types. CVR for LU and PU test samples ranged from 9.1–31.9% (mean: 18.8%) and 13.9–27.0% (mean: 18.5%), respectively, indicating limited reproducibility in 3-HPMA analysis for both sample types. Re-calculation of the PU results by applying an embedded calibration (EC), derived from the reported peak areas for the LU test samples, somewhat improved the CVR values (range: 9.6–28.8%, mean: 16.7%). It is concluded that the intra-laboratory variation (repeatability) in the determination of 3-HPMA in urine is in general acceptable in the participating laboratories, while the inter-laboratory variability requires further improvement. The relatively small reduction in the inter-laboratory variability (sR and CVR) by applying an EC suggests that other methodological factors than the standard reference material for 3-HPMA have to be addressed to achieve further improvement in reproducibility.

Improvement in B1+ Homogeneity and Average Flip Angle Using Dual-Source Parallel RF Excitation for Cardiac MRI in Swine Hearts.

Cardiac MRI may benefit from increased polarization at high magnetic field strength of 3 Tesla but is challenged by increased field inhomogeneity. Initial human studies have shown that the radiofrequency (RF) excitation field (B1 +) used for signal excitation in the heart is both inhomogeneous and significantly lower than desired, potentially leading to image artifacts and biased quantitative measures. Recently, multi-channel transmit systems have been introduced allowing localized patient specific RF shimming based on acquired calibration B1 + maps. Some prior human studies have shown lower than desired mean flip angles in the hearts of large patients even after RF shimming. Here, 100 cardiac B1 + map pairs before and after RF shimming were acquired in 55 swine. The mean flip angle and the coefficient of variation (CV) of the flip angle in the heart were determined before and after RF shimming. Mean flip angle, CV, and RF shim values (power ratio and phase difference between the two transmit channels) were tested for correlation with cross sectional body area and the Right-Left/Anterior-Posterior ratio. RF shimming significantly increased the mean flip angle in swine heart from 74.4±6.7% (mean ± standard deviation) to 94.7±4.8% of the desired flip angle and significantly reduced CV from 0.11±0.03 to 0.07±0.02 (p<<1e-10 for both). These results compare well with several previous human studies, except that the mean flip angle in the human heart only improved to 89% with RF shimming, possibly because the RF shimming routine does not consider safety constraints in very large patients. Additionally, mean flip angle decreased and CV increased with larger cross sectional body area, however, the RF shimming parameters did not correlate with cross sectional body area. RF shim power ratio correlated weakly with Right-Left/Anterior-Posterior ratio but phase difference did not, further substantiating the need for subject specific cardiac RF shimming.

Electron microscopy of laser capsulotomy edge: Interplatform comparison

To perform a morphological comparison of capsulotomy edges generated by commercially available femtosecond lasers with manual capsulorhexis. Private clinic. Experimental study. Capsules were collected using the following laser platforms and software versions: Lensx pre-soft-fit (version 2.16), Lensx post-soft-fit (version 2.20), Victus I (version 2.5), Victus II (version 2.7SP2), Catalys (version 2.15.13), and 10 manual. Scanning electron microscopy images were analyzed for the coefficient of variation (CoV) of pixilation along the capsule edge and homogeneity using gray-level co-occurrence matrix analysis. A qualitative assessment for anomalies, such as tags, was also made. The mean CoV values from the regression analysis showed the manual edge (n = 10) (101.6% ± 0.6% [SD]) was smoother than the edges created with Lensx pre-soft-fit (105.2% ± 1.2%) (P<.001), Lensx post-soft-fit (102.7% ± 1.4%) (P=.04), Victus I (104.9% ± 0.9%) (P<.001), Catalys (104.5% ± 1.6%) (P<.001), and Victus II (104.7% ± 1.6%) platforms. All lasers (0.19 to 0.23) (P<.001) except the Lensx post-soft-fit (0.25 ± 0.03) (P=.23) generated less homogenous capsulotomies than the manual technique (0.27 ± 0.04). Tags occurred with Lensx pre-soft-fit (5/10), Lensx post-soft-fit (1/10), Victus I (1/4), and Victus II (3/10) platforms. Misdirected pulses were seen with the Catalys (4/10) and Victus II (4/10) platforms, which used fluid interfaces. Laser capsulotomies are approaching the smoothness of the manual capsulorhexis. The Lensx post-soft-fit platform showed the least anomalies and the smallest difference for the CoV and homogeneity metrics compared with the manual method. No author has a financial or proprietary interest in any material or method mentioned.