			Home About us Contact

Repeatability Coefficient (repeatability + coefficient)

Distribution by Scientific Domains

Medical Sciences	87%

Selected Abstracts

Quantitative analysis of MRI signal abnormalities of brain white matter with high reproducibility and accuracy

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2002
Xingchang Wei MD
Abstract Purpose To assess the reproducibility and accuracy compared to radiologists of three automated segmentation pipelines for quantitative magnetic resonance imaging (MRI) measurement of brain white matter signal abnormalities (WMSA). Materials and Methods WMSA segmentation was performed on pairs of whole brain scans from 20 patients with multiple sclerosis (MS) and 10 older subjects who were positioned and imaged twice within 30 minutes. Radiologist outlines of WMSA on 20 sections from 16 patients were compared with the corresponding results of each segmentation method. Results The segmentation method combining expectation-maximization (EM) tissue segmentation, template-driven segmentation (TDS), and partial volume effect correction (PVEC) demonstrated the highest accuracy (the absolute value of the Z-score was 0.99 for both groups of subjects), as well as high interscan reproducibility (repeatability coefficient was 0.68 mL in MS patients and 1.49 mL in aging subjects). Conclusion The addition of TDS to the EM segmentation and PVEC algorithms significantly improved the accuracy of WMSA volume measurements, while also improving measurement reproducibility. J. Magn. Reson. Imaging 2002;15:203,209. © 2002 Wiley-Liss, Inc. [source]

Comparison of the USCOM ultrasound cardiac output monitor with pulmonary artery catheter thermodilution in patients undergoing liver transplantation,

LIVER TRANSPLANTATION, Issue 7 2008
Lai-Sze Grace Wong
The aim of the study was to compare the standard technique of cardiac output determination by pulmonary artery catheter thermodilution (PAC-TD) with a noninvasive ultrasound Doppler monitor (USCOM Pty., Ltd., Coffs Harbour, Australia) in surgery for liver transplantation. We wished to determine if the degree of accuracy would allow the ultrasound cardiac output monitor (USCOM) to be used as an alternative monitor in a clinical setting in which wide fluctuations in cardiac output could be expected. This was a prospective method comparison study, with 71 paired measurements obtained in 12 patients undergoing liver transplantation in a university teaching hospital. Bland-Altman analysis of the 2 techniques showed a bias of 0.39 L/minute, with the USCOM cardiac output lower compared with that of PAC-TD. The bias was small and did not vary with the magnitude of the cardiac output. The 95% limits of agreement were ,1.47 and 2.25 L/minute. There was good repeatability for USCOM measurements, with a repeatability coefficient of 0.43 for USCOM versus 0.77 for PAC-TD. We conclude that USCOM is acceptable for the clinical determination of noninvasive cardiac output, particularly in situations in which tracking changes over time is more important than knowing the precise value. However, the utility of USCOM is limited by its inability to measure pulmonary artery pressure. Liver Transpl 14:1038,1043, 2008. © 2008 AASLD. [source]

How should we estimate driving pressure to measure interrupter resistance in children?

PEDIATRIC PULMONOLOGY, Issue 9 2007
MB ChB, P. Seddon BSc
Abstract Interrupter resistance (Rint) is a widely used measure of airway caliber, but concerns remain about repeatability and sensitivity. Some Rint variability may derive from the linear back-extrapolation algorithm (LBE 30/70) usually used to estimate driving pressure. To investigate whether other methods of estimating driving pressure could improve repeatability and sensitivity, we studied 39 children with asthma. Two measurements of Rint,each the median of 10 interruptions,were made 5 min apart, and 14 children had a third measurement after bronchodilator (RintBD). Mouth pressure transients were analyzed using several algorithms, to compare the magnitude, repeatability, and sensitivity to bronchodilator change of Rint values yielded. Algorithms taking driving pressure from later in the transient, predictably, yielded higher values of Rint than those which back-extrapolated to time of valve closure. Algorithms which did not rely on back-extrapolation, including mean oscillation pressure (MOP) and mean plateau pressure (MP 30/70) had better repeatability. Sensitivity to detect change, calculated as ratio of bronchodilator response to repeatability coefficient (,Rint/CR), was also better for non-extrapolating algorithms: MP 30/70 1.67, LBE 30/70 1.28 (P,=,0.0004). Measuring Rint using techniques other than conventional back-extrapolation may give more consistent and clinically useful results, and these approaches merit further exploration. Pediatr Pulmonol. 2007; 42:757,763. © 2007 Wiley-Liss, Inc. [source]

The Measurement of the QT and QTc on the Neonatal and Infant Electrocardiogram: A Comprehensive Reliability Assessment

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009
B.S., Robert M. Gow M.B.
Background: An electrocardiogram has been proposed to screen for prolonged QT interval that may predispose infants to sudden death in the first year of life. Understanding the reliability of QT interval measurement will inform the design of a screening program. Methods: Three pediatric cardiologists measured the QT/RR intervals on 60 infant electrocardiograms (median age 46 days), from leads II, V5 and V6 on three separate occasions, 7 days apart, according to a standard protocol. The QTc was corrected by Bazett's (QTcB), Fridericia's (QTCFrid), and Hodges' (QTcH) formulae. Intraobserver and interobserver reliability were assessed by intraclass correlation coefficients (ICC), limits of agreement and repeatability coefficients for single, average of two and average of three measures. Agreement for QTc prolongation (> 440 msec) was assessed by kappa coefficients. Results: QT interval intraobserver ICC was 0.86 and repeatability coefficient was 25.9 msec; interobserver ICC increased from 0.88 for single observations to 0.94 for the average of 3 measurements and repeatability coefficients decreased from 22.5 to 16.7 msec. For QTcB, intraobserver ICC was 0.67, and repeatability was 39.6 msec. Best interobserver reliability for QTcB was for the average of three measurements (ICC 0.83, reproducibility coefficient 25.8 msec), with further improvement for QTcH (ICC 0.92, reproducibility coefficient 16.69 msec). Maximum interobserver kappa for prolonged QTc was 0.77. Misclassification around specific cut points occurs because of the repeatability coefficients. Conclusions: Uncorrected QT measures are more reliable than QTcB and QTCFrid. An average of three independent measures provides the most reliable QT and QTc measurements, with QTcH better than QTcB. [source]

Repeatability of hematocrits and body mass of Gray Catbirds

JOURNAL OF FIELD ORNITHOLOGY, Issue 1 2010
Margret I. Hatch
ABSTRACT Hematocrits may provide information about the physiological condition of birds, but, to be a useful measure, information is needed concerning how hematocrits vary among individuals and over time. We examined the repeatability of hematocrits in a population of Gray Catbirds (Dumetella carolinensis) in Pennsylvania at several time scales and also examined the repeatability of body mass, another measure commonly used as an indicator of condition. Both hematocrit (r= 0.64) and mass (r= 0.65) were repeatable (P < 0.01) for first captures between years and between first and second captures within a year (r= 0.41 and r= 0.50, respectively; P < 0.01), but not repeatable (P > 0.05) between captures in different months within a year (r= 0.11 for both). Repeatability of both measures differed by sex and age. Females exhibited repeatability of hematocrit and body mass only between years, while male hematocrits were repeatable between years and between first and second captures within a season. Male mass was repeatable for all time periods. Hematocrits of younger birds were repeatable between captures within a season and their body mass was repeatable between months and weeks while hematocrits of older birds were not repeatable and their body mass was repeatable only between captures in a season. Our results indicate that hematocrits and body mass had similar repeatability coefficients overall, but that hematocrits of Gray Catbirds were a consistent trait of individuals only across years. Because repeatability between captures and months depended on sex and age, we conclude that the hematocrit is a useful measure of individual performance only in limited circumstances. RESUMEN El hematocrito podría proveer información sobre la condición física de las aves pero para ser una medida útil se necesita información sobre como el hematocrito varia entre individuos y a través del tiempo. Examinamos la repetibilidad del hematocrito en una población de Dumetella carolinensis en Pennsylvania durante diferentes escalas temporales. También examinamos la repetibilidad del peso corporal, otra medida comúnmente usada como indicador de la condición del individuo. El hematocrito (r= 0.64) y el peso corporal (r= 0.65) eran repetibles (P < 0.01) para las primeras capturas entre años y entre la primera y segunda captura dentro del año (r= 0.41 y r= 0.50, respectivamente; P < 0.01), pero no eran repetibles (P > 0.05) entre capturas realizadas en diferentes meses dentro del año (r= 0.11 para los dos). La repetibilidad de las dos medidas difiere por sexo y edad. Las hembras se caracterizaron por tener repetibilidad del hematocrito y del peso corporal solo entre años, mientras que el hematocrito de los machos era repetible entre años y entre la primera y segunda captura dentro de la temporada. El peso corporal de los machos era repetible durante todos los periodos a través del tiempo. El hematocrito de las aves mas jóvenes era repetible entre capturas dentro de la temporada y su peso corporal era repetible entre meses y semanas, mientras que el hematocrito de las aves mayores no era repetible y su peso corporal era repetible solo entre capturas dentro de la temporada. Nuestros resultados indican que los hematocritos y el peso corporal en general tuvieron coeficientes de repetibilidad similares, pero que los hematocritos de D. carolinensis eran un rasgo consistente de los individuos solo entre años. Por la razón que la repetibilidad entre capturas y meses dependía del sexo y edad, concluimos que el hematocrito es una medida útil del performance individual solo en circunstancias limitadas. [source]

DNA Status on Thawed Semen from Fighting Bull: A Comparison Between the SCD and the SCSA Tests

REPRODUCTION IN DOMESTIC ANIMALS, Issue 3 2009
F Martínez-Pastor
Contents The assessment of sperm chromatin status is compulsory in a complete spermiogram. Here we applied the sperm chromatin structure assay (SCSA) and the sperm chromatin dispersion (SCD) test to assess the chromatin status of three fighting bulls. Cryopreserved semen (two straws/bull) were analysed by duplicate after thawing and after 6 h at 37°C with and without oxidative stress (1 mm FE2+). Results (SCD: percentage of spermatozoa with halo; SCSA: SD-DFI, %DFI and HDS) were analysed for differences between bulls and treatments, sensitivity and specificity (receiver operating characteristic curves) and repeatability (repeatability coefficients as 2SD of duplicate differences).%DFI for the three bulls was below 2% at 0 h, indicating no risk for fertility according to previous reports. It increased slightly for two of the bulls after FE2+ treatment (%DFI < 5%) and more pronouncedly for the other bull (C, %DFI,10%), which merits further investigation. SCD rendered higher percentage of halos for bull C, but could not discriminate between samples with and without oxidizing treatment (AUC: 0.52). SCSA (%DFI) showed a high discriminating ability between treatments (AUC: 0.96). The repeatability coefficient was also higher for SCD (5.9) than for %DFI (1.8), indicating lower repeatability for SCD. Overall, %DFI might be the most useful parameter for assessing sperm chromatin on fighting bull. SCD might yield different information than SCSA, hence further research is warranted. [source]

The Measurement of the QT and QTc on the Neonatal and Infant Electrocardiogram: A Comprehensive Reliability Assessment

Repeatability of local forearm vasoconstriction to endothelin-1 measured by venous occlusion plethysmography

BRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 4 2002
Fiona E. Strachan
Aims ,We ,investigated ,the ,repeatability ,of ,the ,forearm ,blood ,flow ,response ,to intra-arterial infusion of endothelin-1 (ET-1), assessed by venous occlusion plethysmography. Methods In eight healthy men (aged 18,50 years), on four separate occasions, ET-1 (2.5 or 10 pmol min,1) was infused for 120 min via a 27 SWG cannula sited in the brachial artery of the nondominant arm. Each dose level was administered twice on consecutive visits. The dose order was randomized. Results are expressed as percentage change from baseline at 120 min (mean ± s.e. mean). Results ET-1 caused significant vasoconstriction (P < 0.0001 anova) at both doses (38 ± 3%, 2.5 pmol min,1 and 62 ± 3%, 10 pmol min,1; mean visit 1 and 2). There was no difference in the response to either dose on repeated challenge. Responses appeared to be less variable when expressed as percentage change in the ratio of blood flow (infused:noninfused) in both arms than as percentage change in blood flow in the infused arm alone, as indicated by repeatability coefficients (15% vs 21%, 2.5 pmol min,1 and 11% vs 13%, 10 pmol min,1; ratio vs infused arm alone). Conclusions We have shown dose-dependent vasoconstriction in the forearm vascular bed to intra-arterial infusion of ET-1 and that this response is less variable when expressed as percentage change in the ratio of forearm blood flow than percentage change in the infused arm. These data should also provide useful information to determine the power of early clinical pharmacology studies investigating the activity of endothelin receptor antagonists. [source]