Lung Clearance Index in Adults and Children With Cystic Fibrosis
Katherine O’NeillMichael M. TunneyE. JohnstonStephen RowanD.G. DowneyJacqueline C. RendallAlastair ReidIan BradburyJ.S. ElbornJudy Bradley
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Coefficient of variation
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Rationale: Lung function deterioration is a major cause of morbidity and mortality in patients with cystic fibrosis (CF).Spirometry is an important tool for monitoring lung function decline and early detection of exacerbations.The use of tele-services has increased recently and played a pivotal role in healthcare access to the vulnerable populations during the COVID-19 pandemic.The accuracy and reliability of using home spirometry for CF patients remain unclear.We hypothesized that in stable CF patients, lung function measured using home spirometry would correlate with baseline lung function measured by clinic spirometry.Methods: We prospectively enrolled patients with stable CF who received handheld ZEPHYRx® home spirometers from May-December 2020.We analyzed home spirometry efforts that met ATS Standards.Baseline characteristics were retrospectively collected from the electronic health records including baseline lung function -calculated as the average of the best two clinic spirometry efforts, when available.Only home spirometry measurements of patients on stable therapy were included (elexacaftor/tezacaftor/ivacaftor).Pearson's correlation coefficients were performed to evaluate the relationship between baseline lung function and mean home spirometry measures.We measured both point estimates and mean values for home spirometry.Results: We analyzed a cohort of 77 patients, which consisted of 40 (51.9%)females and 76 (98.7%)Non-Hispanic Caucasian.The mean age of patients was 34.3 years (SD 10.9).The average baseline percent predicted FEV 1 measured in clinic (FEV 1 (c)) was 68.7 (SD 23.2) and the average percent predicted FEV 1 measured using home spirometry (FEV 1 (h)) was 66.6 (SD 20.9).The mean baseline percent predicted FVC in clinic (FVC(c)) was 73.5 (SD 21.7) whereas the mean FVC measured using home spirometry (FVC(h)) was 83.5 (SD 18.5).Mean peak expiratory flow rates (PEFR) measured in a subset of patients (n= 48) at baseline in clinic (PEF(c)) was 7.2 l/min (SD 19.1), and mean PEFR measured using home spirometry (PEF(h)) was 7.0 l/min (SD 1.8).A very strong correlation was found between FEV 1 (c) and FEV 1 (h) (r = 0.95, P< 0.001).Whereas strong correlations were found between FVC(c) and FVC(h) (r = 0.713, P<0.001) and PEF(c) and PEF(h) (r= 0.895, P<0.001).Conclusion: In a cohort of stable CF patients, the spirometric measures (FEV 1 , FVC and PEF) using a home spirometry device have stronger or better correlations with the corresponding baseline lung function.Home spirometry is a reliable device in monitoring CF patients.Further studies are ongoing exploring the variability and repeatability of home spirometry measures.
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The aim of this study was to investigate intra- and interspecimen repeatability of an experimental procedure, which determines elastic and viscoelastic properties of knee ligaments. The collateral ligaments from sheep were used and the repeatability was evaluated in terms of the coefficient of variation. The results indicated a good intraspecimen repeatability (the coefficient of variation generally less than 5%), whereas the interspecimen repeatability was lower (coefficient of variation of about 50%). In conclusion, since the intraspecimen coefficient of variation was low the test procedure was assumed to be repeatable.
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A reliable clinical test should give similar results when repeated on the same patient. Repeatability data, however, can be presented in several ways, giving apparently different results. We compared two approaches--the coefficient of variation, and the SD ratio (SD of repeat measurements/SD of subject means). Repeat measurements of two published studies of cardiovascular autonomic function response were analysed. The test measurements were divided into two groups: group A tests, for which no response results in a zero output (includes measurements of differences or changes); and group B tests, for which no response results in a unity or other non-zero output (includes measurements of ratios). Data were obtained from 10 normal and 25 diabetic subjects. There were significant differences between the coefficients of variation of the two groups of tests for the normal subjects (p < 0.01) and for the diabetic subjects (p < 0.01). Low coefficients of variation were more likely to belong to group B (ratio measurements) than to be an estimate of good repeatability. The calculation of the coefficient of variation was adapted to ensure that the test calculation tended to zero with low autonomic function. There was a strong relationship, especially with the diabetic subjects, between repeatability calculated from the adapted coefficient of variation and from the SD ratio (normal subjects, r = 0.63; diabetic subjects, r = 0.91). The calculation of coefficient of variation is often misused, and low coefficients of variation presented in the literature may not represent good repeatability of a clinical test.
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The purpose was to investigate differences in reliability of running economy measurements between familiar and unfamiliar shoes. Thirty-seven runners were included who all ran in familiar and unfamiliar running shoes while running economy was measured at steady state using a treadmill. Each participant was tested on two different visits (three sessions in total), with two trials in each of the three shoe conditions completed at each visit. Coefficient of variation, standard deviation of differences, and limits of agreement of running economy were used to quantify the repeatability (within-visit variation) and reproducibility (between-visit variation). The coefficient of variation showed a marginal difference in reproducibility across shoe conditions, whereas no differences were seen in coefficient of variation, standard deviation of the differences, or limits of agreement for repeatability across shoes. All three shoe conditions showed greater repeatability than reproducibility for running economy, and enhanced repeatability at visit 3 compared to visit 2. Our results indicate that familiarisation to shoes might not be needed for reliable measurements of running economy. Based on our results, when evaluating benefits in running shoes we suggest that running economy be assessed within the same day. Further, our data suggest a beneficial effect of using multiple familiarisation sessions if small differences between shoe conditions are expected.
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Objectives: To determine and compare the repeatability and reproducibility of anterior scleral parameters measured by the corneoscleral profile (CSP) module of Pentacam in keratoconus (KC) and control eyes. Methods: This is a prospective observational study. Thirty KC participants (30 eyes) and 24 control participants (24 eyes) were examined three times using the CSP. Sagittal height mean (SHM), sagittal height astigmatism (SHA), and mean bulbar slope (BSM) were measured in 12 mm and 16 mm chord lengths. The repeatability and reproducibility of these measurements were also assessed. Coefficients of variation (CoV), intraclass correlation coefficient (ICC), coefficient of repeatability (CoR1), and coefficient of reproducibility (CoR2) were adopted to assess the reliability. Results: In the KC and control groups, SHM showed high repeatability and reproducibility (coefficients of variation [CoVs]≤0.96%, intraclass correlation coefficient [ICCs]≥0.97), and SHM of control eyes showed higher repeatability and reproducibility than that of KC eyes at 12 mm chord length (KC group, CoRs ranged from 35.56 μm to 43.52 μm, control group, ranged from 23.50 μm to 30.31 μm) and 16 mm chord length (KC group, CoRs ranged from 79.54 μm to 81.58 μm, control group, ranged from 48.25 μm to 66.10 μm). Mean bulbar slope also showed high repeatability and reproducibility (CoVs≤3.65%, CoRs≤2.64). Furthermore, the SHA of control eyes showed higher repeatability and reproducibility when compared with KC eyes (control group: CoVs≤29.95%, KC group: CoVs≥32.67%). Conclusions: Keratoconus and control eyes demonstrated high repeatability and reproducibility when using CSP measurements, which may prove helpful in fitting contact lenses.
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Scheimpflug principle
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Abstract Objective To assess the intra‐ and interobserver reproducibility of songographic measurement of fetal femur length between 10 and 16 weeks of gestation. Methods Femur length was measured three times by the same trained observer in each fetus of 136 pregnant women. A second trained observer then repeated the measurements. The coefficient of variation, intraclass correlation coefficient and repeatability coefficient with 95% CIs were calculated for each observer and between the two observers. Results The inter‐ and intraobserver repeatabilities of femur length were good. For interobserver correlation, the coefficient of variation was 4.6% (95% CI, 3.0–6.2), the intraclass correlation coefficient was 0.82 (95% CI, 0.69–0.95) and the repeatability coefficient was 2.1 (95% CI, 1.8–2.7). For intraobserver correlation, the coefficient of variation was 4.2% (95% CI, 3.2–5.6), the intraclass correlation coefficient was 0.91 (95% CI, 0.75–0.97) and the repeatability coefficient was 3.23 (95% CI, 2.33–3.86) for Observer 2. Similar results were obtained for the other observer. Conclusion Transvaginal femur length measurement is technically feasible and easy to perform between 10 and 16 weeks of gestation. The high degree of intra‐ and interobserver repeatability indicates it to be a reproducible method. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
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The role of spirometry in the assessment of lung function and the diagnosis of lung disease should not be underestimated. Accurate measurements require a proficient operator trained in the use of the equipment and in supporting patients throughout.
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