Some office spirometers showed an apparent good agreement with the standard spirometers (low bias), but the visual inspection of the Bland and Altman plot revealed a proportional difference. In other words, there was a significant relationship between the mean difference and the average values, as indicated in Table 3 by a statistically significant coefficient of correlation. In the example of Figure 2, FEV1 was underestimated for small values and overestimated for larger values. As shown in Tables 3 and 4, a proportional difference was observed in one device for FVC, in four devices for FEV1, and in two devices for FEV1/FVC. fully
The pooled results of this survey are shown in the on-line supplementary material. The overall user friendliness of the tested devices was judged to be good. The information provided by the spirometers was in general very complete. The clusters of questions with strongly favorable answers were those about the general properties of the software, the completeness of the displayed information, and the automated tests of quality assurance. We noted intermediate positive answers for the following clusters: patient administrative data facilities, comparison of successive spirometrics and facilities for use at home visits. Rather unfavorable scores were given to the functions for export of data.
We report the results of a multicentric study of 10 office spirometers compared according to both their technical and user-friendliness characteristics. The precision of FEV1 measurement was good in the majority of these small spirometers and was comparable to the values obtained with the standard diagnostic devices. However, the repeatability of FVC was generally poorer, and the broad limits of agreement of FVC or FEV1 observed between some office spirometers and the standard devices may preclude the interchangeability of the results. All the office spirometers presented in this study received the label “meets ATS recommendations. This label supposes that the spirometers were checked by a series of predetermined flow-volume curves via a computer-driven piston pump. In the standardization of spirometry published recently, the ATS/European Respiratory Society (ERS) task force recommends that spirometers should be evaluated using a computer-driven mechanical syringe or its equivalent.
Figure 2. Bland and Altman plot of the relationship between mean FEV1 and the difference in FEV1 between the standard spirometers and the EasyOne. There was a significant linear relationship between these variables (straight oblique line), indicating a proportional difference between the devices. The origin of the points is identified (the three centers). For sake of clarity, the limits of agreement are not shown.