4.2.1 Clinical impact of measurement error
The initial concerns that the findings of Wyler et al.1 about the measurement error in the widely used MBW software Spiroware 3.2.1 could tremendously change utility of LCI in clinical routine, can be rejected by our findings. We could show, that clinimetric properties of LCI still hold, even though with a slightly smaller magnitude based on overall lower LCI values. This is due to the measurement principle of the test, the indirect N2-calculation was found to be overestimated by the cross-sensitivity error in the O2 and CO2- signals, leading to a prolongation of the washout with falsely high LCI values. Our results suggest that clinical interpretation of LCI change is not affected by the correction of this error. As such we can support recently published results from clinical trials and extent the interpretation into the clinical application2.
4.2.2 Impact on feasibility (success rates of measurements)
Since the correction of the gas measurement error results in shorter washouts, we were able to reanalyze all our trials with the corrected software version 22. Thus, also in clinical practice, overall N2-MBW will become shorter with the corrected software which might increase the feasibility of the test, especially in the younger and possibly less cooperative age range but also in patients with more advanced disease and longer washout times13,22.
4.2.3 Impact on Repeatability
Overall, we found short-and midterm repeatability17,18 to be similar after cross-sensitivity correction, and thus limits for intervisit changes and variability to be unaffected. Within-subject between test standard deviation remained independent of the magnitude of LCI, which preserves the property of LCI to guide individual clinical decisions.