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      Peak expiratory flow rate as a surrogate for forced expiratory volume in 1 second in COPD severity classification in Thailand

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          Abstract

          Background

          There are limited studies directly comparing correlation and agreement between peak expiratory flow rate (PEFR) and forced expiratory volume in 1 second (FEV 1) for severity classification of COPD. However, clarifying the role of PEFR as a surrogate of COPD severity classification instead of FEV 1 is essential in situations and areas where spirometry is not routinely available.

          Purpose

          To evaluate the agreement between FEV 1 and PEFR using Global initiative for chronic Obstructive Lung Disease (GOLD) severity classification criteria.

          Materials and methods

          This cross-sectional study included stable COPD patients. Both absolute values and % predicted FEV 1 and % predicted PEFR were obtained from the same patients at a single visit. The severity of COPD was classified according to GOLD criteria. Pearson’s correlation coefficient was used to examine the relationship between FEV 1 and PEFR. The agreement of % predicted FEV 1 and % predicted PEFR in assigning severity categories was calculated using Kappa statistic, and identification of the limits of agreement was by Bland–Altman analysis. Statistical significance was set at P-value <0.05.

          Results

          Three hundred stable COPD patients were enrolled; 195 (65.0%) male, mean age 70.4±9.4 years, and mean % predicted FEV 1 51.4±20.1. Both correlations between the % predicted FEV 1 and PEFR as well as the absolute values were strongly significant ( r=0.76, P<0.001 and r=0.87, P<0.001, respectively). However, severity categories of airflow limitation based on % predicted FEV 1 or PEFR intervals were concordant in only 179 patients (59.7%). The Kappa statistic for agreement was 0.41 (95% confidence interval, 0.34–0.48), suggesting unsatisfied agreement. The calculated limits of agreement were wide (+27.1% to −28.9%).

          Conclusion

          Although the correlation between FEV 1 and PEFR measurements were strongly significant, the agreement between the two tests was unsatisfied and may influence inappropriate clinical decision making in diagnosis, severity classification, and management of COPD.

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          Most cited references 19

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          Statistical methods for assessing agreement between two methods of clinical measurement.

          In clinical measurement comparison of a new measurement technique with an established one is often needed to see whether they agree sufficiently for the new to replace the old. Such investigations are often analysed inappropriately, notably by using correlation coefficients. The use of correlation is misleading. An alternative approach, based on graphical techniques and simple calculations, is described, together with the relation between this analysis and the assessment of repeatability.
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            Spirometry in primary care practice: the importance of quality assurance and the impact of spirometry workshops.

            To determine the quality of spirometry performed in primary care practice and to assess the impact of formal training. Randomized, controlled prospective interventional study. Primary care practice, Auckland City, New Zealand. Thirty randomly selected primary care practices randomized to "trained" or "usual" groups. One doctor and one practice nurse were nominated to participate from each practice. "Trained" was defined as participation in an "initial" spirometry workshop at week 0 and a "maintenance of standards" workshop at week 12. "Usual" was defined as no formal training until week 12, when participants they attended the same "initial" workshop provided for the trained group. The study duration was 16 weeks. Each practice was provided with a spirometer to be used at their clinical discretion. Spirometry data were uploaded weekly and analyzed using American Thoracic Society (ATS) criteria for acceptability and reproducibility. The workshops were assessed objectively with practical and written assessments, confirming a significant training effect. However, analysis of spirometry performed in clinical practice by the trained practitioners revealed three acceptable blows in only 18.9% of patient tests. In comparison, 5.1% of patient tests performed by the usual practitioners had three acceptable blows (p<0.0001). Only 13.5% of patient tests in the trained group and 3.4% in the usual group (p<0.0001) satisfied full acceptability and reproducibility criteria. However, 33.1% and 12.5% of patient tests in the trained and usual groups, respectively (p<0.0001), achieved at least two acceptable blows, the minimum requirement. Nonacceptability was largely ascribable to failure to satisfy end-of-test criteria; a blow of at least 6 s. Visual inspection of the results of these blows as registered on the spirometer for the presence of a plateau on the volume-time curve suggests that < 15% were acceptable. Although a significant training effect was demonstrated, the quality of the spirometry performed in clinical practice did not generally satisfy full ATS criteria for acceptability and reproducibility. Further study would be required to determine the clinical impact. However, the ATS guidelines allow for the use of data from unacceptable or nonreproducible maneuvers at the discretion of the interpreter. Since most of the failures were end-of-test related, the FEV1 levels are likely to be valid. Our results serve to emphasize the importance of effective training and quality assurance programs to the provision of successful spirometry in primary care practice.
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              Relationship between airway obstruction and respiratory symptoms in adult asthmatics.

              To characterize the relationship between symptoms and the degree of airway obstruction as determined by the FEV1 and peak expiratory flow (PEF) in a cohort of adult patients attending a university-based urban asthma clinic. Each of six current asthma symptoms, including cough, dyspnea, wheeze, chest tightness, sputum production, and nocturnal awakening was rated by patients on a 0 (none) to 4 (constant) scale at initial and first follow-up clinic evaluations. Spirometry and PEF were measured at the initial clinic visit and PEF was measured at all follow-up visits. Sixty-seven adult patients with chronic asthma. Asthma symptoms did not correlate with the degree of airway obstruction as determined by the FEV1 (percent predicted FEV1 vs total symptoms: r=0.143; p=0.263; n=70) and only correlated poorly with PEF (percent predicted PEF vs total symptoms: r=0.384; p=0.0029; n=58). Subjective wheezing was the best individual predictor of the level of airway obstruction in this group of patients. When reassessed an average of 7.9 weeks later, patients reported significant improvement in several symptoms, including those of wheeze, chest tightness, dyspnea, and nocturnal awakening. However, this symptomatic improvement was not associated with improvement in the level of airway obstruction. Asthma symptoms correlate poorly with the level of airway obstruction as determined by the FEV1 and PEF. Following treatment, subjective improvement in asthma symptoms may occur without improvement in the level of airway obstruction. These results support the recommendation to measure airway obstruction objectively when assessing adult patients with chronic asthma.
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                Author and article information

                Journal
                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                1176-9106
                1178-2005
                2015
                25 June 2015
                : 10
                : 1213-1218
                Affiliations
                Division of Pulmonary, Critical Care and Allergy, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
                Author notes
                Correspondence: Chaicharn Pothirat, Division of Pulmonary, Critical Care and Allergy, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, 110 Inthavaroros Rd. Sriphum, Maung Chiang Mai district, Chiang Mai 50200, Thailand, Tel +66 53 946 228, Fax +66 53 895 117, Email cpothira@ 123456med.cmu.ac.th
                Article
                copd-10-1213
                10.2147/COPD.S85166
                4485793
                © 2015 Pothirat et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

                The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

                Categories
                Original Research

                Respiratory medicine

                spirometry, chronic obstructive pulmonary disease, agreement

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