Bland-Altman Mean Difference Research Articles

B-009 Verification of Result Interchangeability Between Two Analyzers in the Determination of Uric Acid and Urea

Abstract Background Uric acid and urea are two parameters widely used in the diagnosis and management of renal pathology. In our laboratory, they are determined using Atellica Solution® analyzers (Siemens Healthineers). After validating a new Siemens equipment, Atellica CI®, it is essential to ensure result interchangeability in our laboratory accredited by ISO 15189:2012. Objectives evaluate the interchangeability of results for uric acid and urea measured by Atellica Solution® and CI® analyzers. Methods A total of 40 serum samples from patients with uric acid values between 1.3 and 15.2 mg/dL, and another 40 serum samples from patients with urea values between 7 and 142 mg/dL were processed in parallel. Statistical analysis of the results was performed using Passing-Bablok regression and Bland Altman mean difference analysis with Method Validator Version 1.19. Results are expressed with their 95% confidence interval. Results Uric Acid: After analyzing Bland-Altman differences, a statistically significant slight systematic error was found, as the 95% CI does not include 0, with slightly higher results in CI 1900®. Regarding Passing-Bablok regression analysis, there were no systematic errors of constant type (since the 95% CI of the intercept includes 0) but a discreet significant proportional systematic error was observed (the confidence interval of the slope does not include 1).Urea: In Bland-Altman analysis, a discreet systematic error was observed as the 95% CI of the mean difference does not include the null value. Regarding Passing-Bablok regression analysis, there were no systematic errors of constant type (since the 95% CI of the intercept includes 0) or proportional type (since the 95% CI of the slope includes 1), indicating interchangeability between both analyzers. Conclusions The results obtained by both Atellica Solution® and CI® analyzers for uric acid and urea assays are interchangeable since the statistically significant differences observed can be considered analytically and clinically insignificant.

A-220 Method Intercomparison Study between Atellica Solution® and CI® Analyzers for HDL and LDL Methods

Abstract Background After validating a new Siemens equipment, the Atellica CI®, it is essential to ensure result interchangeability in our laboratory accredited by ISO 15189:2012. Objectives verify if the results of the HDL and LDL methods measured by Atellica Solution® and CI® analyzers are interchangeable and could be used interchangeably on both instruments Methods 40 patient samples were selected for each assay, with results distributed across the entire measurement range and analyzed by both instruments. Result evaluation was conducted using the statistical program Method Validator v.19. To determine the degree of agreement between the instruments, a Bland-Altman mean difference analysis and a Passing-Bablok regression were performed. Statistics are expressed with their 95% confidence intervals (CI). Results HDL: After analyzing the Bland-Altman differences, a systematic error was found as the mean difference between the results obtained by Atellica Solution® and CI® was 0.686, with higher results in CI 1900®. Regarding the Passing Bablok analysis, constant systematic differences were observed as the confidence interval of the intercept does not include the zero value, and statistically significant proportional differences based on the slope whose 95% CI does not include the value 1.LDL: After analyzing the Bland-Altman differences, a systematic error was found as the mean difference between the results obtained by Atellica and CI® was -3.16, with higher results in Atellica Solution®. Regarding the Passing Bablok analysis, there were no systematic differences of constant type as the confidence interval of the intercept includes the zero value, but there were proportional differences based on the slope whose 95% CI does not include the value 1. Conclusions After evaluating the results, it is concluded that Atellica Solution® and CI® analyzers are interchangeable for HDL and LDL assays despite the presence of a systematic error, as the observed difference is not clinically significant.

B-011 Intermethod Comparison Verification between Atellica Solution® and CI® Analyzers for Amylase and Glucose Methods

Abstract Background The objective of this study is to verify if the results of the Amylase and Glucose methods, measured by two different analyzers: Atellica Solution® and CI® (Siemens Healthineers), are interchangeable. Methods To carry out the intermethod comparison study of the Amylase and Glucose methods, 40 patient samples were selected for each assay, with concentrations across the entire measurement range. Statistical analysis was performed using Method Validator v.19 software, through Bland-Altman mean difference analysis and Passing-Bablok regression. Statistics are expressed with their 95% confidence intervals (CI). Results AMYLASE: After analyzing the Bland-Altman differences, a statistically significant systematic error was found, as the mean difference between the results obtained by Atellica Solution® and CI® was 28.1 with a 95% CI that does not include the null value, with higher results in CI®. Regarding the Passing Bablok analysis, systematic differences, both proportional and constant, were observed as the confidence interval of the intercept does not include the zero value, and that of the slope does not include the value 1.GLUCOSE: After Bland-Altman analysis, a systematic error was found, as the mean difference between the results obtained by Atellica Solution® and CI® was 2.1, with slightly higher results in CI®. Regarding the Passing Bablok analysis, there were no systematic differences of constant type since the confidence interval of the intercept includes the zero value, and a slight proportional systematic error based on the slope as its 95% CI does not include the value 1. Conclusions After evaluating the results, it is concluded that the Atellica Solution® and CI® analyzers are not interchangeable for the Amylase assay, so new reference values should be established. For the Glucose assay, both analyzers are interchangeable as the observed difference does not exceed our quality specification.

Assessment of postural sway with accelerometers: A comparison with force plate measures

Introduction & Purpose Postural control is essential for maintaining balance during static and dynamic tasks. It is typically measured by centre of pressure (CoP) deviations using a ground reaction force plate (FP). Alternatively, more affordable and accessible accelerometer-based measures have been proposed. However, no consensus on the best protocol exists (Pinho et al., 2019). This study investigates the feasibility of assessing postural sway using linear acceleration data, considering sensor placement, task difficulty and analysed parameters. Methods The University of Vienna Ethics Committee approved this study (Ref. Nr. 01108). Ten healthy adults (6 M/4 F; 37.9 ± 14.8 years; BMI = 23.3 ± 2.3) performed eleven balance tasks, seven easy tasks from the Berg Balance Scale and four harder tasks with eyes closed, each lasting 20 seconds. Postural sway was assessed using a FP and five inertial measurement units (IMUs) attached to the upper spine (C7), lower spine (L1), sacrum and both thighs. Data were synchronously collected at 1500 Hz, zeroed, band pass filtered (3rd order Butterworth, 0.3-10 Hz; Martinez-Mendez et al., 2012), and cropped to 19 s. Outcomes included CoP path length, root mean square of sway amplitude in the anteroposterior (AP) and mediolateral (ML) directions for the FP, and RMS of the linear acceleration in AP and ML directions, along with their sum, for the ACC. Combinations of the two AP, two ML and two overall parameters were analysed by winsorised Pearson correlations and Bland Altman limits of agreement of z-scores for each task and for each sensor site. Fisher's Z-transformed correlation coefficients and limits of agreement were compared across task difficulty, parameter combinations, and sensor placement sites using a 3-way ANOVA. Results Pearson coefficients correlating the ACC parameters with the FP parameters averaged 0.60 (95% CI [0.54, 0.66]) for the easy tasks and 0.78 (95% CI [0.726, 0.84]) for the hard tasks, with no significant differences between sensor sites. A significant interaction (p < 0.001) was found between task difficulty and parameter combination. Simple main effect analysis showed no difference between correlations of AP, ML and overall parameters for hard tasks but for easy tasks, where overall parameters showed the highest correlation, followed by ML and then AP parameters, all differing significantly from each other. The Bland Altman mean difference of z-scores between FP and ACC parameters was on average -0.002 (95% CI [-0.027, 0.024]). The lower and upper limits of agreement were on average -0.72 (95% CI [-0.84, -0.62]) and 0.73 (95% CI [0.62, 0.83]) respectively. Discussion The correlations between FP and ACC were higher during more challenging tasks, while the limits of agreement were broader and less precise in these tasks (data not shown). No optimal sensor placement site was identified as correlation and agreement between the two methods did not differ significantly between sites. The broad limits of agreement suggest relatively low precision of ACC measures compared to FP. Overall parameters often outperformed ML and AP parameters in terms of correlation and precision. Conclusion Accelerometer-based measures of postural sway showed high correlations with force plate measures but low precision when tasks where difficult enough to challenge participants’ balance. Sensor placement site did not influence correlation and precision. References Pinho, A. S., Salazar, A. P., Hennig, E. M., Spessato, B. C., Domingo, A., & Pagnussat, A. S. (2019). Can we rely on mobile devices and other gadgets to assess the postural balance of healthy individuals? A systematic review. Sensors, 19(13), Article 13. https://doi.org/10.3390/s19132972 Martinez-Mendez, R., Sekine, M., & Tamura, T. (2012). Postural sway parameters using a triaxial accelerometer: Comparing elderly and young healthy adults. Computer Methods in Biomechanics and Biomedical Engineering, 15(9), 899–910. https://doi.org/10.1080/10255842.2011.565753

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.

The NARCOguide index – a novel parameter for monitoring depth of hypnosis during anaesthesia/sedation with propofol

BACKGROUND The NARCOguide algorithm calculates an EEG-derived index to monitor the hypnotic component of anaesthesia. OBJECTIVE This study evaluates the accuracy of the index calculated by NARCOguide against the Narcotrend index as a reference. Secondly, the automatic detection of burst-suppression patterns as represented by the burst suppression ratio was compared. DESIGN Comparative study to assess the agreement between two medical devices. SETTING At two study centres, patient data were collected from a total of 40 adults receiving general anaesthesia or sedation with propofol. INTERVENTIONS Patients underwent either general anaesthesia for oral surgery with propofol/remifentanil/rocuronium (study centre 1) or light general anaesthesia/deep sedation with propofol alone for laryngoscopic upper airway exploration (study centre 2). MAIN OUTCOME MEASURES In a posthoc analysis, the NARCOguide index was compared with the Narcotrend index. Comparison was made after averaging over 1 min at defined clinical markers using classic linear least squares regression and Bland–Altman plots. Precision and recall for the detection of burst suppression were determined using human scoring as a reference. RESULTS Data analysis showed good agreement [Bland–Altman mean difference (MD) = −2.3; limits of agreement = −27.1, to +22.4; n = 1209] and high correlation (r 2 = 0.76) between the depth of anaesthesia index calculated by NARCOguide and Narcotrend. The precision and recall of NARCOguide and Narcotrend for the detection of burst suppression were in a similar range. Over the entire dataset, the NARCOguide algorithm showed higher precision and recall than the Narcotrend algorithm (56% vs. 36% and 68% vs. 58%, respectively). CONCLUSION The NARCOguide index can be used to monitor the hypnotic component of anaesthesia in patients undergoing general anaesthesia or sedation with propofol, with a performance similar to that of the Narcotrend index. TRIAL REGISTRATION Trial registration number: 18020, regulatory authority: Ethikkommission der bayerischen Landesärztekammer, chairman: Dr med. Gerald Quitterer, applicant: Dr Gert Küchler, date of approval: 12. Jun 2018, completion of data collection: 12 December 2018, study completion: 31 March 2022.

Concordance Analysis of the Pressure Chamber and Tubomanometer According to Estève for the Determination of Eustachian Tube Opening Pressure.

For the diagnosis of Eustachian tube dysfunction (ETD), clinical procedures such as tympanometry, micro-otoscopy, and maneuvers according to Toynbee and Valsalva only allow an indirect assessment for the moment. With a prevalence of up to 5%, the selection of patients with ETD and its subtypes is clinically relevant. Dynamic methods of Eustachian tube function assessment include a hypo/hyperbaric pressure chamber and Estève's tubomanometer (TMM). One method of assessing ETD is the evaluation of Eustachian tube opening pressure (ETOP). We performed a concordance analysis between pressure chamber and TMM to determine ETOP. For this purpose, we analyzed the measurements of both methods from 28 healthy subjects using Bland-Altman plots, regression according to Passing-Bablok and Lin's concordance correlations coefficient. The maximum tolerated clinical deviation of measured values was set at 10%. A maximum of 53 measurements of ETOP between pressure chamber and TMM were compared. Mean ETOP for TMM was 28.7 hPa, passive opening was 32 hPa, Toynbee maneuver was 28.4 hPa, and Valsalva maneuver was 54.6 hPa. Concordance analysis revealed following results: passive opening versus TMM: Bland-Altman mean difference 3.3 hPa, limits of agreement ±31.8 hPa; Passing-Bablok regression y = 0.67 x + 9.36; Lin's rccc = 0.18. Toynbee versus TMM: Bland-Altman mean difference 0.7 hPa, limits of agreement ±35.8 hPa; Passing-Bablok regression y = 0.47x + 14.03; Lin's rccc = 0.14. Valsalva versus TMM: Bland-Altman mean difference 24.2 hPa, limits of agreement ±117.5 hPa; Passing-Bablok regression y = 0.17x + 25.12; Lin's rccc = 0.18. Estève's tubomanometer and pressure chamber measurements of ETOP are not concordant. The two methods cannot be interchanged without reservation.

A metric for quantitative evaluation of glioma margin changes in magnetic resonance imaging.

Gliomas differ from meningiomas in their margins, most of which are not separated from the surrounding tissue by a distinct interface. To characterize the margins of gliomas quantitatively based on the margin sharpness coefficient (MSC) is significant for clinical judgment and invasive analysis of gliomas. The data for this study used magnetic resonance image (MRI) data from 67 local patients and 15 open patients to quantify the intensity of changes in the glioma margins of the brain using MSC. The accuracy of MSC was assessed by consistency analysis and Bland-Altman test analysis, as well as invasive correlations using receiver operating characteristic (ROC) and Spearman correlation coefficients for subjects. In grading the tumors, the mean MSC values were significantly lower for high-grade gliomas (HGG) than for low-grade gliomas (LGG). The concordance correlation between the measured gradient and the actual gradient was high (HGG: 0.981; LGG: 0.993), and the Bland-Altman mean difference at the 95% confidence interval (HGG: -0.576; LGG: 0.254) and the limits of concordance (HGG: 5.580; LGG: 5.436) indicated no statistical difference. The correlation between MSC and invasion based on the margins of gliomas showed an AUC of 0.903 and 0.911 for HGG and LGG, respectively. The mean Spearman correlation coefficient of the MSC versus the actual distance of invasion was -0.631 in gliomas. The relatively low MSC on the blurred margins and irregular shape of gliomas may help in benign-malignant differentiation and invasion prediction of gliomas and has potential application for clinical judgment.

Quantitative perfusion and water transport time model from multi b-value diffusion magnetic resonance imaging validated against neutron capture microspheres.

Quantification of perfusion in ml/100 g/min, rather than comparing relative values side-to-side, is critical at the clinical and research levels for large longitudinal and multi-center trials. Intravoxel incoherent motion (IVIM) is a non-contrast magnetic resonance imaging diffusion-based scan that uses a multitude of -values to measure various speeds of molecular perfusion and diffusion, sidestepping inaccuracy of arterial input functions or bolus kinetics. Questions remain as to the original of the signal and whether IVIM returns quantitative and accurate perfusion in a pathology setting. This study tests a novel method of IVIM perfusion quantification compared with neutron capture microspheres. We derive an expression for the quantification of capillary blood flow in ml/100 g/min by solving the three-dimensional Gaussian probability distribution and defining water transport time (WTT) as when 50% of the original water remains in the tissue of interest. Calculations were verified in a six-subject pre-clinical canine model of normocapnia, induced hypercapnia, and middle cerebral artery occlusion (ischemic stroke) and compared with quantitative microsphere perfusion. Linear regression analysis of IVIM and microsphere perfusion showed agreement (slope = 0.55, intercept = 52.5, ) with a Bland-Altman mean difference of . Linear regression between dynamic susceptibility contrast mean transit time and IVIM WTT asymmetry in infarcted tissue was excellent (, intercept = 0.3, ). Strong linear agreement was found between IVIM and reference standard infarct volume (slope = 1.01, ). The simulation of cerebrospinal fluid (CSF) suppression via inversion recovery returned a blood signal reduced by 82% from combined T1 and T2 effects. The accuracy and sensitivity of IVIM provides evidence that observed signal changes reflect cytotoxic edema and tissue perfusion and can be quantified with WTT. Partial volume contamination of CSF may be better removed during post-processing rather than with inversion recovery.

The Role of Artificial Intelligence in Coronary Calcium Scoring in Standard Cardiac Computed Tomography and Chest Computed Tomography With Different Reconstruction Kernels.

To assess the correlation of coronary calcium score (CS) obtained by artificial intelligence (AI) with those obtained by electrocardiography gated standard cardiac computed tomography (CCT) and nongated chest computed tomography (ChCT) with different reconstruction kernels. Seventy-six patients received standard CCT and ChCT simultaneously. We compared CS obtained in 4 groups: CS CCT , by the traditional method from standard CCT, 25 cm field of view, 3 mm slice thickness, and kernel filter convolution 12 (FC12); CS AICCT , by AI from the standard CCT; CS ChCTsoft , by AI from the non-gated CCT, 40 cm field of view, 3 mm slice thickness, and a soft kernel FC02; and CS ChCTsharp , by AI from CCT image with same parameters for CS ChCTsoft except for using a sharp kernel FC56. Statistical analyses included Spearman rank correlation coefficient (ρ), intraclass correlation (ICC), Bland-Altman plots, and weighted kappa analysis (κ). The CS AICCT was consistent with CS CCT (ρ = 0.994 and ICC of 1.00, P < 0.001) with excellent agreement with respect to cardiovascular (CV) risk categories of the Agatston score (κ = 1.000). The correlation between CS ChCTsoft and CS ChCTsharp was good (ρ = 0.912, 0.963 and ICC = 0.929, 0.948, respectively, P < 0.001) with a tendency of underestimation (Bland-Altman mean difference and 95% upper and lower limits of agreements were 329.1 [-798.9 to 1457] and 335.3 [-651.9 to 1322], respectively). The CV risk category agreement between CS ChCTsoft and CS ChCTsharp was moderate (κ = 0.556 and 0.537, respectively). There was an excellent correlation between CS CCT and CS AICCT , with excellent agreement between CV risk categories. There was also a good correlation between CS CCT and CS obtained by ChCT albeit with a tendency for underestimation and moderate accuracy in terms of CV risk assessment.

Evaluation of newly-developed glycated hemoglobin clinical analytic reagents and chromatography column on Tosoh HLC-723 G8 Analyzer

ObjectiveTo evaluate the performance of newly developed glycated hemoglobin (HbA1c) clinical analytic reagents and HPLC columns, applied on Tosoh HLC-723 G8 Analyzer. MethodsNewly developed reagents and columns were used on a Tosoh HLC-723 G8 Analyzer (standard mode) system to measure both of qulity contorls and the clinical blood samples to evaluate the performances of these newly developed prodcuts including precision, accuracy, linearity, carryover, bias evaluation, correlation with commercial reagents, and stability according to CLSI recommendations. ResultsThe CV of intra-assay precision and inter-assay precision of quality control and clinical blood sample assays using Lirimax products were both less than 3.00%. And the REs of accuracy were less than 6.00%. Linearity: R2 = 0.9993 in the concentration range 4.77%–14.67%. Carryover: 0.05%. The Bland-Altman mean difference: −0.003583% HbA1c (CI: 0.07398: −0.08115); Passing-Bablok regression: y = 1.0022(0.9984:1.006)x-0.01097(-0.03776: 0.01582), R2 = 0.9996. Stability evaluation was also acceptable. ConclusionThe performance of newly developed products was well evaluated for HbA1c measurement on a TOSOH G8 Analyzer which shows excellent suitability for clinical assay.

The impact of the image conversion factor and image centration on retinal vessel geometric characteristics.

This study aims to use fundus image material from a long-term retinopathy follow-up study to identify problems created by changing imaging modalities or imaging settings (e.g., image centering, resolution, viewing angle, illumination wavelength). Investigating the relationship of image conversion factor and imaging centering on retinal vessel geometric characteristics (RVGC), offers solutions for longitudinal retinal vessel analysis for data obtained in clinical routine. Retinal vessel geometric characteristics were analyzed in scanned fundus photographs with Singapore-I-Vessel-Assessment using a constant image conversion factor (ICF) and an individual ICF, applying them to macula centered (MC) and optic disk centered (ODC) images. The ICF is used to convert pixel measurements into μm for vessel diameter measurements and to establish the size of the measuring zone. Calculating a constant ICF, the width of all analyzed optic disks is included, and it is used for all images of a cohort. An individual ICF, in turn, uses the optic disk diameter of the eye analyzed. To investigate agreement, Bland-Altman mean difference was calculated between ODC images analyzed with individual and constant ICF and between MC and ODC images. With constant ICF (n = 104 eyes of 52 patients) the mean central retinal equivalent was 160.9 ± 17.08 μm for arteries (CRAE) and 208.7 ± 14.7.4 μm for veins (CRVE). The individual ICFs resulted in a mean CRAE of 163.3 ± 15.6 μm and a mean CRVE of 219.0 ± 22.3 μm. On Bland-Altman analysis, the individual ICF RVGC are more positive, resulting in a positive mean difference for most investigated parameters. Arteriovenous ratio (p = 0.86), simple tortuosity (p = 0.08), and fractal dimension (p = 0.80) agreed well between MC and ODC images, while the vessel diameters were significantly smaller in MC images (p < 0.002). Scanned images can be analyzed using vessel assessment software. Investigations of individual ICF versus constant ICF point out the asset of utilizing an individual ICF. Image settings (ODC vs. MC) were shown to have good agreement.

Observer agreement of imaging measurements used for evaluation of dentofacial deformity in juvenile idiopathic arthritis.

To examine the precision of imaging measures commonly used to assess mandibular morphology in children and adolescents with juvenile idiopathic arthritis (JIA). Secondly, to compare cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI) in the measurement of condylar height. Those included were children diagnosed with JIA during 2015-18 who had had an MRI, a CBCT of the temporomandibular joints (TMJs) and a lateral cephalogram (ceph) of the head within one month of each other. Agreement within and between observers and methods was examined using Bland-Altman mean-difference plots and 95% limits of agreement (LOA). A 95% LOA within 15% of the sample mean was considered acceptable. Minimal detectable change (MDC) within and between observers was estimated. 90 patients (33 males) were included, with a mean age of 12.8 years. For MRI, intra- and interobserver 95% LOA were relatively narrow for total mandibular length: 9.6% of the sample mean. For CBCT, condylar height, both intra- and interobserver 95% LOA were wide: 16.0 and 28.4% of the sample mean, respectively. For ceph, both intra- and interobserver 95% LOA were narrow for the SNA-angle and gonion angle: 5.9 and 8% of the sample mean, and 6.2 and 6.8%, respectively. We have identified a set of precise measurements for facial morphology assessments in JIA, including one MRI-based (total mandibular length), one CBCT-based (condylar height), and three ceph-based. Condylar height was higher for MRI than for CBCT; however, the measurement was too imprecise for clinical use. MDC was also determined for a series of measurements.

Fully Automated Transcranial Doppler Ultrasound for Middle Cerebral Artery Insonation

Background: Transcranial Doppler ultrasound (TCD) is utilized in the assessment of neurological conditions in clinical environments such as the intensive care unit and emergency department. However, obstacles for widespread use of TCD include a lack of trained registered vascular technologists (RVT) and operator variability. We present a study comparing RVT and a fully automated robotic TCD system (NovaGuide rTCD) for insonation of the middle cerebral artery (MCA).Methods: A trained RVT and rTCD sequentially collected bilateral MCA cerebral blood flow velocity (CBFV) from 86 healthy subjects. Mean CBFV (mCBFV) and the signal quality assessment (SQA) acquired manually by RVT and autonomously via rTCD were compared. Comparison metrics evaluated include mean accuracy ratio (MAR), and Bland-Altman mean-difference (MD) between rTCD and RVT with paired t-Test for significance. Bootstrapping was used in the accuracy ratio and mean-time to best signal computations to establish 95% confidence intervals.Results: The mCBFVs and SQAs found by rTCD compared to RVT had MAR of 99.7% (97.7-101.7%) and 102.7% (101.1-104.8%), respectively. The rTCD mean-time to best-quality signal was 0.87 min (0.71-1.05) (RVT was not timed). The mean-difference scores for mCBFV and SQA were MD=-0.43cm/s (&lt;i&gt;p&lt;/i&gt;=0.053) and MD=-0.36 (&lt;i&gt;p&lt;/i&gt;=0.61), respectively. The rTCD had a 3.5% no-window failure rate compared to RVT no-window rate of 4.1%.Conclusion: Comparison of bilateral TCD signals collected by rTCD and RVT demonstrated equivalence in mCBFV and signal quality, suggesting rTCD’s potential to expand utility of TCD in clinical settings that are resource-limited.

Open Reimplementation of the BIS Algorithms for Depth of Anesthesia.

BIS (a brand of processed electroencephalogram [EEG] depth-of-anesthesia monitor) scores have become interwoven into clinical anesthesia care and research. Yet, the algorithms used by such monitors remain proprietary. We do not actually know what we are measuring. If we knew, we could better understand the clinical prognostic significance of deviations in the score and make greater research advances in closed-loop control or avoiding postoperative cognitive dysfunction or juvenile neurological injury. In previous work, an A-2000 BIS monitor was forensically disassembled and its algorithms (the BIS Engine) retrieved as machine code. Development of an emulator allowed BIS scores to be calculated from arbitrary EEG data for the first time. We now address the fundamental questions of how these algorithms function and what they represent physiologically. EEG data were obtained during induction, maintenance, and emergence from 12 patients receiving customary anesthetic management for orthopedic, general, vascular, and neurosurgical procedures. These data were used to trigger the closely monitored execution of the various parts of the BIS Engine, allowing it to be reimplemented in a high-level language as an algorithm entitled ibis. Ibis was then rewritten for concision and physiological clarity to produce a novel completely clear-box depth-of-anesthesia algorithm titled openibis . The output of the ibis algorithm is functionally indistinguishable from the native BIS A-2000, with r = 0.9970 (0.9970-0.9971) and Bland-Altman mean difference between methods of -0.25 ± 2.6 on a unitless 0 to 100 depth-of-anesthesia scale. This precision exceeds the performance of any earlier attempt to reimplement the function of the BIS algorithms. The openibis algorithm also matches the output of the native algorithm very closely ( r = 0.9395 [0.9390-0.9400], Bland-Altman 2.62 ± 12.0) in only 64 lines of readable code whose function can be unambiguously related to observable features in the EEG signal. The operation of the openibis algorithm is described in an intuitive, graphical form. The openibis algorithm finally provides definitive answers about the BIS: the reliance of the most important signal components on the low-gamma waveband and how these components are weighted against each other. Reverse engineering allows these conclusions to be reached with a clarity and precision that cannot be obtained by other means. These results contradict previous review articles that were believed to be authoritative: the BIS score does not appear to depend on a bispectral index at all. These results put clinical anesthesia research using depth-of-anesthesia scores on a firm footing by elucidating their physiological basis and enabling comparison to other animal models for mechanistic research.

Magnetic resonance imaging overestimates patellar height compared with radiographs.

To evaluate the inter-observer and inter-method reliability for patellar height measurements between conventional radiographs (CR) and magnetic resonance imaging (MRI) using one or two slices. This was a reliability study, with 60 patients divided in two groups: 30 patients with patellar instability (patella group) and 30 patients with anterior cruciate ligament or meniscus injury (control group). CR and MRI were evaluated by two independent observers. Insall-Salvati index (IS) and Caton-Deschamps index (CD) were measured using three different methods: CR, one-slice MRI or two-slice MRI. Intra-class correlation coefficients (ICC) were calculated for inter-observer reliability and inter-method reliability. Bland-Altman agreement was also calculated. The inter-observer reliability was very good for the IS with ICCs of 0.93, 0.84 and 0.82, for the CR, one-slice MRI and two-slice MRI, respectively. Similarly, for the CD the ICCs were good, 0.76, 0.80 and 0.75 for the CR, one-slice MRI and two-slice MRI, respectively. No differences were found between the patella and the control group. The inter-method analysis results were: ICCs for IS (0.83, 0.86, 0.93) and CD (0.72, 0.82, 0.83), for the comparisons of CR/one-slice MR, CR/two-slice MRI and one-slice MRI/two-slice MRI, respectively. The Bland-Altman mean differences showed an 8% and a 7% increase on IS values with one-slice MRI and two-slice MRI compared to CR results, while the increase was of 9% and 1% in CD for the respective comparisons with CR. MRI can overestimate patellar height compared to CR, as much as an 8% increase in Insall-Salvati values when using one- or two-slice MRI measurements, and up to a 9% increase in Caton-Deschamps value when using the one-slice MRI method. It is recommended to use the CR as the preferred method when measuring patellar height. III.

Ultrafast Computation of Left Ventricular Ejection Fraction by Using Temporal Intensity Variation in Cine Cardiac Magnetic Resonance.

Cardiac magnetic resonance enables comprehensive cardiac evaluation; however, intense time and labor requirements for data acquisition and processing have discouraged many clinicians from using it. We have developed an alternative image-processing algorithm that requires minimal user interaction: an ultrafast algorithm that computes left ventricular ejection fraction (LVEF) by using temporal intensity variation in cine balanced steady-state free precession (bSSFP) short-axis images, with or without contrast medium. We evaluated the algorithm's performance against an expert observer's analysis for segmenting the LV cavity in 65 study participants (LVEF range, 12%-70%). In 12 instances, contrast medium was administered before cine imaging. Bland-Altman analysis revealed quantitative effects of LV basal, midcavity, and apical morphologic variation on the algorithm's accuracy. Total computation time for the LV stack was <2.5 seconds. The algorithm accurately delineated endocardial boundaries in 1,132 of 1,216 slices (93%). When contours in the extreme basal and apical slices were not adequate, they were replaced with manually drawn contours. The Bland-Altman mean differences were <1.2 mL (0.8%) for end-diastolic volume, <5 mL (6%) for end-systolic volume, and <3% for LVEF. Standard deviation of the difference was ≤4.1% of LV volume for all sections except the midcavity in end-systole (8.3% of end-systolic volume). We conclude that temporal intensity variation-based ultrafast LVEF computation is clinically accurate across a range of LV shapes and wall motions and is suitable for postcontrast cine SSFP imaging. Our algorithm enables real-time processing of cine bSSFP images on a commercial scanner console within 3 seconds in an unobtrusive automated process.

Development of a short food frequency questionnaire to assess diet quality in UK adolescents using the National Diet and Nutrition Survey

BackgroundUK adolescents consume fewer fruits and vegetables and more free sugars than any other age group. Established techniques to understand diet quality can be difficult to use with adolescents because of high participant burden. This study aimed to identify key foods that indicate variation in diet quality in UK adolescents for inclusion in a short food frequency questionnaire (FFQ) and to investigate the associations between adolescent diet quality, nutritional biomarkers and socio-demographic factors.MethodsDietary, demographic and biomarker data from waves 1–8 of the National Diet and Nutrition Survey rolling programme were used (n=2587; aged 11–18 years; 50% boys; n=≤997 biomarker data). Principal component analysis (PCA) was applied to 139 food groups to identify the key patterns within the data. Two diet quality scores, a 139-group and 20-group, were calculated using the PCA coefficients for each food group and multiplying by their standardised reported frequency of consumption and then summing across foods. The foods with the 10 strongest positive and 10 strongest negative coefficients from the PCA results were used for the 20-group score. Scores were standardised to have a zero mean and standard deviation of one.ResultsThe first PCA component explained 3.0% of variance in the dietary data and described a dietary pattern broadly aligned with UK dietary recommendations. A correlation of 0.87 was observed between the 139-group and 20-group scores. Bland-Altman mean difference was 0.00 and 95% limits of agreement were − 0.98 to 0.98 SDs. Correlations, in the expected direction, were seen between each nutritional biomarker and both scores; results attenuated slightly for the 20-group score compared to the 139-group score. Better diet quality was observed among girls, non-white populations and in those from higher socio-economic backgrounds for both scores.ConclusionsThe diet quality score based on 20 food groups showed reasonable agreement with the 139-group score. Both scores were correlated with nutritional biomarkers. A short 20-item FFQ can provide a meaningful and easy-to-implement tool to assess diet quality in large scale observational and intervention studies with adolescents.

Repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography in myopic and postphotorefractive keratectomy eyes.

To investigate repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography (OCT) in myopic and postphotorefractive keratectomy (PRK) eyes. Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Prospective observational study. Total corneal, epithelial, and stromal thicknesses were measured using RTVue-XR OCT with Pachymetry + Cpwr (6.0 mm algorithm) and PachymetryWide (9.0 mm algorithm) scan patterns. The repeatability of 25 zones of 9.0 mm map and 17 zones of 6.0 mm map and the agreement between measurements of these 2 algorithms were calculated. Ninety-five myopic and 117 post-PRK patients were evaluated. By the 9.0 mm algorithm, coefficient of variation (CoV) for total cornea was 2.33% or lesser and 2.49% or lesser and for epithelium was 5.14% or lesser and 5.18% or lesser; and by the 6.0 mm algorithm, CoV for total cornea was 1.80% or lesser and 2.59% or lesser and for epithelial thickness was 3.08% or lesser and 4.80% or lesser in myopic and post-PRK eyes, respectively. Bland-Altman mean difference for epithelial thickness was 0.69 or lesser and 1.16 or lesser and 95% limits of agreement for epithelial thickness was 6.81 or lesser and 8.56 or lesser in myopic and post-PRK eyes, respectively. Good repeatability was seen in measurements of total corneal, stromal, and epithelial thicknesses by both algorithms. Agreement of the 2 algorithms in central zone was also good. However, large range of variation in paracentral thickness measurements did not allow us to consider these algorithms as interchangeable.

Feasibility of three dimensional power Doppler ultrasonography methods to assess placental perfusion

ObjectivesGiven the crucial role of the placenta in establishing a healthy pregnancy, reliable non-invasive methods to measure placental perfusion are desirable. The aim of this study is to determine the reproducibility and potential bias in different three-dimensional power Doppler (3DPD) methods assessing placenta perfusion. MethodsTen singleton pregnancies around 16 weeks of gestation, with an anteriorly located placenta and centrally inserted umbilical cord were included in this study. Eight different combinations of a specific placental sweep and sonobiopsy method were used to evaluate placental perfusion. Vascularization index (VI), flow index (FI) and vascularization-flow index (VFI) were determined offline using the 4D-view program. Reproducibility and repeatability of the methods, expressed as correlation coefficients and Bland-Altman mean differences, were calculated. Differences between sampling methods were analyzed using t-test or Mann-Whitney U test. ResultsIntra- and inter-class correlation coefficient (CC) was highest when using a spherical centrally placed sonobiopsy of 2 cm3 in a whole placenta sweep (method 1; IntraCC VI 0.985, FI 0.769, VFI 0.993, InterCC VI 0.986, FI 0.784, VFI 0.987). Overall, intraCCs were higher compared to interCCs. Lowest mean differences in VI and FI were found comparing spherical to manual sonobiopsies, whereas the mean differences in VFI were lowest when comparing central versus peripheral located sonobiopsies. Comparing the three vascular indices, best median intra- and interCC and lowest mean differences were found for VFI. ConclusionsThree dimensional placental vascularization analysis showed best reproducibility using whole placental sweep volume and centrally located, spherical sonobiopsy of 2 cm3.