Percent Limits Of Agreement Research Articles

Evaluation of Non-Compressive Transvaginal Cervical Elastography as a Quantitative Imaging Biomarker in Pregnancy: A Repeatability and Reliability Analysis.

Non-compressive strain elastography has been proposed as a novel quantitative imaging biomarker for assessing the structure and function of the cervix. The current study aims to assess the repeatability, and intra- and inter-observer reliability of transvaginal non-compressive cervical strain elastography in a clinical setting. We conducted a dual-phase single-center prospective feasibility study of singleton gestations >16-weeks gestation that required a clinically-indicated transvaginal ultrasound. Each study participant, n = 43 in phase 1 and n = 13 in phase 2, had elastography performed by two trained observers that each performed multiple image acquisitions. We performed a multivariable regression to adjust for changes in clinical characteristics between study phases and calculated the repeatability coefficients, limits of agreement, and intraclass correlations for each quantitative elastography parameter. We compared quantitative elastography parameters to cervical length measurements, acquired from the same images. The repeatability coefficients and percent limits of agreement were wide for all of the quantitative elastography parameters, demonstrating poor repeatability. Intraclass correlation coefficients were poor-moderate for both intra-observer (0.31-0.77) and inter-observer reliability (0.35-0.77) in both study phases, while cervical length showed excellent reliability with intraclass correlations consistently >0.90. Non-compressive transvaginal strain cervical elastography did not demonstrate adequate repeatability or reliability. Our results highlight the importance of rigorously assessing novel quantitative imaging biomarkers before clinical application.

A paired comparison of nerve dimensions using B-Mode ultrasound and shear wave elastography during regional anaesthesia.

Shear wave elastography (SWE) presents nerves in colour, but the dimensions of its colour maps have not been validated with paired B-Mode nerve images. Our primary objective was to define the bias and limits of agreement of SWE with B-Mode nerve diameter. Our secondary objectives were to compare nerve area and shape, and provide a clinical standard for future application of new colour imaging technologies such as artificial intelligence. Eleven combined ultrasound-guided regional nerve blocks were conducted using a dual-mode transducer. Two raters outlined nerve margins on 110 paired B-Mode and SWE images every second for 20 s before and during injection. Bias and limits of agreement were plotted on Bland-Altman plots. We hypothesized that the bias of nerve diameter would be <2.5% and that the percent limits of agreement would lie ±0.67% (2 SD) of the bias. There was no difference in the bias (95% confidence interval (CI) limits of agreement) of nerve diameter measurement, 0.01 (-0.14 to 0.16) cm, P = 0.85, equivalent to a 1.4% (-56.6% to 59.5) % difference. The bias and limits of agreement were 0.03 (-0.08 to 0.15) cm2, P = 0.54 for cross-sectional nerve area; and 0.02 (-0.03 to 0.07), P = 0.45 for shape. Reliability (ICC) between raters was 0.96 (0.94-0.98) for B-Mode nerve area and 0.91 (0.83-0.95) for SWE nerve area. Nerve diameter measurement from B-Mode and SWE images fell within a priori measures of bias and limits of agreement.

Within-day variability on short and long walking tests in persons with multiple sclerosis

ObjectiveTo compare within-day variability of short (10m walking test at usual and fastest speed; 10MWT) and long (2 and 6-minute walking test; 2MWT/6MWT) tests in persons with multiple sclerosis. DesignObservational study. SettingMS rehabilitation and research centers in Europe and US within RIMS (European network for best practice and research in MS rehabilitation). SubjectsAmbulatory persons with MS (Expanded Disability Status Scale 0–6.5). InterventionSubjects of different centers performed walking tests at 3 time points during a single day. Main measures10MWT, 2MWT and 6MWT at fastest speed and 10MWT at usual speed.Ninety-five percent limits of agreement were computed using a random effects model with individual pwMS as random effect. Following this model, retest scores are with 95% certainty within these limits of baseline scores. ResultsIn 102 subjects, within-day variability was constant in absolute units for the 10MWT, 2MWT and 6MWT at fastest speed (+/−0.26, 0.16 and 0.15m/s respectively, corresponding to +/−19.2m and +/−54m for the 2MWT and 6MWT) independent on the severity of ambulatory dysfunction. This implies a greater relative variability with increasing disability level, often above 20% depending on the applied test. The relative within-day variability of the 10MWT at usual speed was +/−31% independent of ambulatory function. ConclusionsAbsolute values of within-day variability on walking tests at fastest speed were independent of disability level and greater with short compared to long walking tests. Relative within-day variability remained overall constant when measured at usual speed.

The reliability, minimal detectable change and concurrent validity of a gravity-based bubble inclinometer and iphone application for measuring standing lumbar lordosis

Purpose: To investigate the reliability, minimal detectable change (MDC90) and concurrent validity of a gravity-based bubble inclinometer (inclinometer) and iPhone® application for measuring standing lumbar lordosis. Methods: Two investigators used both an inclinometer and an iPhone® with an inclinometer application to measure lumbar lordosis of 30 asymptomatic participants. Results: ICC models 3,k and 2,k were used for the intrarater and interrater analysis, respectively. Good interrater and intrarater reliability was present for the inclinometer with Intraclass Correlation Coefficients (ICC) of 0.90 and 0.85, respectively and the iPhone® application with ICC values of 0.96 and 0.81. The minimal detectable change (MDC90) indicates that a change greater than or equal to 7° and 6° is needed to exceed the threshold of error using the iPhone® and inclinometer, respectively. The concurrent validity between the two instruments was good with a Pearson product-moment coefficient of correlation (r) of 0.86 for both raters. Ninety-five percent limits of agreement identified differences ranging from 9° greater in regards to the iPhone® to 8° less regarding the inclinometer. Conclusion: Both the inclinometer and iPhone® application possess good interrater reliability, intrarater reliability and concurrent validity for measuring standing lumbar lordosis. This investigation provides preliminary evidence to suggest that smart phone applications may offer clinical utility comparable to inclinometry for quantifying standing lumbar lordosis. Clinicians should recognize potential individual differences when using these devices interchangeably.

Interchangeability of macular thickness measurements between different volumetric protocols of Spectralis optical coherence tomography in normal eyes

To evaluate in healthy eyes the interchangeability of retinal thickness measurements resulting from different protocols of Spectralis optical coherence tomography (OCT, Heidelberg Engineering, Germany). Three different central volumetric protocols were performed in one session by one single operator in a randomly selected eye of 31 healthy adults (range, 19-30 years): (1) area 6 × 6 mm, 25 scan pattern (SP), (2) area 6 × 6 mm, 49 SP, (3) area 6 × 3 mm, 97 SP. Nine ETDRS areas were analyzed, except outer areas for 97 SP. Interclass correlation coefficients (ICC) and limits of agreement (Bland-Altman) were calculated. Mean minimal foveal thickness was 224.0 ± 15.8 μm and central retinal thickness 280.8 ± 16.5 μm. ICC ranged from 0.973 to 0.993. Ninety-five percent limits of agreement between the protocols were <7 μm in all ETDRS areas. The difference between two measurements never exceeded 9 μm. Spectralis OCT retinal thickness measurements in healthy subjects showed good protocol interchangeability for all tested protocols. Larger differences are to be expected in eyes with macular pathology.

Nurse-determined assessment of cardiac output. Comparing a non-invasive cardiac output device and pulmonary artery catheter: A prospective observational study

Background The accurate measurement of Cardiac output (CO) is vital in guiding the treatment of critically ill patients. Invasive or minimally invasive measurement of CO is not without inherent risks to the patient. Skilled Intensive Care Unit (ICU) nursing staff are in an ideal position to assess changes in CO following therapeutic measures. The USCOM (Ultrasonic Cardiac Output Monitor) device is a non-invasive CO monitor whose clinical utility and ease of use requires testing. Objectives To compare cardiac output measurement using a non-invasive ultrasonic device (USCOM) operated by a non-echocardiograhically trained ICU Registered Nurse (RN), with the conventional pulmonary artery catheter (PAC) using both thermodilution and Fick methods. Design Prospective observational study. Setting and participants Between April 2006 and March 2007, we evaluated 30 spontaneously breathing patients requiring PAC for assessment of heart failure and/or pulmonary hypertension at a tertiary level cardiothoracic hospital. Methods SCOM CO was compared with thermodilution measurements via PAC and CO estimated using a modified Fick equation. This catheter was inserted by a medical officer, and all USCOM measurements by a senior ICU nurse. Mean values, bias and precision, and mean percentage difference between measures were determined to compare methods. The Intra-Class Correlation statistic was also used to assess agreement. The USCOM time to measure was recorded to assess the learning curve for USCOM use performed by an ICU RN and a line of best fit demonstrated to describe the operator learning curve. Results In 24 of 30 (80%) patients studied, CO measures were obtained. In 6 of 30 (20%) patients, an adequate USCOM signal was not achieved. The mean difference (±standard deviation) between USCOM and PAC, USCOM and Fick, and Fick and PAC CO were small, −0.34 ± 0.52 L/min, −0.33 ± 0.90 L/min and −0.25 ± 0.63 L/min respectively across a range of outputs from 2.6 L/min to 7.2 L/min. The percent limits of agreement (LOA) for all measures were −34.6% to 17.8% for USCOM and PAC, −49.8% to 34.1% for USCOM and Fick and −36.4% to 23.7% for PAC and Fick. Signal acquisition time reduced on average by 0.6 min per measure to less than 10 min at the end of the study. Conclusions In 80% of our cohort, USCOM, PAC and Fick measures of CO all showed clinically acceptable agreement and the learning curve for operation of the non-invasive USCOM device by an ICU RN was found to be satisfactorily short. Further work is required in patients receiving positive pressure ventilation.

Exhaled nitric oxide monitoring in COPD using a portable analyzer

Background The exhaled nitric oxide (FeNO) is a non-invasive marker of airway inflammation in asthma. A very recent statement has suggested FeNO as potential outcome in chronic obstructive pulmonary disease (COPD). Recently, a new hand-held FeNO analyzer (NIOX MINO) has been developed. Patients and methods We have evaluated the NIOX MINO in COPD patients and monitored FeNO levels during 1-year assessment in the outpatient setting. Short-term variability in FeNO was compared using a NIOX MINO and a stationary chemiluminescence analyzer (NOA, Sensormedics) in healthy volunteers and COPD patients on two consecutive months. Long-term FeNO variability was assessed on a cohort of 70 COPD outpatients measuring FeNO for 1 year. The intra-individual FeNO coefficient of variation (eNOCoV) was taken as index FeNO long-term variability. Results In COPD there were no significant differences between NIOX MINO and NOA FeNO values recorded at baseline and 1 month later. Ninety five percent limits of agreement between NIOX MINO and NOA were—2.7 and 1.9 ppb with significant reliability ( r=0.96, p<0.0001). Mean FeNO at baseline was 15.0±9.5 ppb. Over the 1-year period the overall mean FeNO was 15.5±10.1 ppb. The long-term eNOCoV was 33.9±16.4% (range 8.1–83.1%), and it was significantly associated with exacerbation rate ( r=0.57, p<0.0001). Conclusion FeNO electrochemical hand-held analyzer is feasible in COPD showing good agreement with stationary chemiluminescence analyzer. COPD patients exhibit a wide range of FeNO levels and a high variability of FeNO over time, which was positively associated with the number of exacerbations.