Do clinimetric properties of LCI change after correction of signal processing?

BACKGROUND: The recently described sensor‐crosstalk error in the multiple‐breath washout (MBW) device Exhalyzer D (Eco Medics AG) could highly influence clinimetric properties and the current interpretation of MBW results. This study reanalyzes MBW data from clinical routine in the corrected software version Spiroware® 3.3.1 and evaluates the effect on outcomes. METHODS: We included nitrogen‐MBW data from healthy children and children with cystic fibrosis (CF) from previously published trials and ongoing cohort studies. We specifically compared lung clearance index (LCI) analyzed in Spiroware 3.2.1 and 3.3.1 with regard to (i) feasibility, (ii) repeatability, and (iii) validity as outcome parameters in children with CF. RESULTS: (i) All previously collected measurements could be reanalyzed and resulted in unchanged feasibility in Spiroware 3.3.1. (ii) Short‐ and midterm repeatability of LCI was similar in both software versions. (iii) Clinical validity of LCI remained similar in Spiroware 3.3.1; however, this resulted in lower values. Discrimination between health and disease was comparable between both software versions. The increase in LCI over time was less pronounced with 0.16 LCI units/year (95% confidence interval [CI] 0.08; 0.24) versus 0.30 LCI units/year (95% CI 0.21; 0.38) in 3.2.1. Response to intervention in children receiving CF transmembrane conductance‐modulator therapy resulted in a comparable improvement in LCI, in both Spiroware versions. CONCLUSION: Our study confirms that clinimetric properties of LCI remain unaffected after correction for the cross‐sensitivity error in Spiroware software.