Evaluation of diagnostic device for obstructive sleep apnea.
نویسنده
چکیده
The article by Bar et al (March 2003)1 reports an evaluation of the Watch PAT100 (WP100) device (Itamar Medical; Caesarea, Israel) for the diagnosis of obstructive sleep apnea. The manner in which the authors have presented their data does not adequately evaluate the accuracy of the WP100 device. The authors have used correlation and Bland-Altman plots to compare calculations of the apnea hypopnea index (AHI) derived from the WP100 and conventional attended polysomnography. Although a statistically significant correlation was found, this does not imply agreement between the two measurements. The finding that there is a statistically significant relationship between the two measurements is not surprising as they are measuring the same thing. The real question is by how much measurements using the new method differ from the old. For this reason, Bland and Altman2 described the use of Bland-Altman plots to assess agreement. A critical part of this analysis is the calculation of the mean difference between the measurements and the limits of agreement ( 2 SDs) and plotting these on the graph. Used in this way the Bland-Altman plot gives a measure of agreement that allows the evaluation of the agreement between two measurements over a range of values. Bar et al1 have included a Bland-Altman plot in their article, but failed to include the mean difference or the limits of agreement. From visual inspection of the data, it appears that there is a large difference between measurements, with the WP100 underscoring events at low AHIs and overscoring events at high AHIs. They report “good agreement” and a “slight tendency” to underscore and overscore events. However, given that the magnitude of the difference between the two measurements is as large as 45 events per hour, with many other points being 10 events per hour, I do not agree with their conclusions. Differences of this magnitude are clinically significant and impact on the diagnosis and treatment of patients. The lack of important data in this article assessing a new diagnostic device reminds us all of the importance of careful evaluation of new technologies before integrating them into clinical practice. Hopefully the initiatives of the Standards for Reporting of Diagnostic Accuracy group will help to improve reporting of new diagnostic techniques in the future.3
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عنوان ژورنال:
- Chest
دوره 124 4 شماره
صفحات -
تاریخ انتشار 2003