Normal Variation in DLCO Biologic Control Measures in a Multi-Center Global Study

Abstract

Background: One step for assuring accuracy of pulmonary function laboratory (PFL) equipment is performing a biologic quality control (BioQC). The American Thoracic Society (ATS) and European Respiratory Society’s (ERS) 2017 standard for D_LCO BioQC requires weekly performance with a coefficient of variation (CV) of 12% based upon a study using 8 individuals. The aim of this study was to assess the D_LCO BioQC %CV results from a large clinical trial. Methods: This study received institutional review board approval from Rush University Medical Center, ORA# 19032007. A D_LCO BioQC program was developed for an inhaled medication study that spanned over 42 months ending in 2018. Onsite training was provided to 114 PFLs from North America, Europe, and Israel using equipment from five different manufacturers. Results were sent to a central repository for expert review. The annual D_LCO %CV was based upon a minimum of 10 D_LCO values separated by at least 5 days with no control for diurnal variation. Each BioQC had to be technically satisfactory according to ATS/ERS 2005 D_LCO standards without failure of other mechanical quality control tests. Descriptive statistics were computed. Paired t-tests were conducted to compare the rate of %CV changes between years and tested at α = .05 using SPSS. Results: Of 217 BioQCs, 168 participants met the inclusion criteria for D_LCO BioQC tests the first year of the study with fewer in subsequent years. As indicated in Table 1, over 90% of %CV values were < 8% and the %CV decreased with experience. There was < 1% change in %CV across the 2-year time span. Conclusions: The D_LCO BioQC %CV standard could be reduced to < 8%. This could improve precision of this important diagnostic test by 33% without impairing the function of PFLs. The PFL BioQC staff do not need to recalculate their %CV more frequently than every two years based upon the low variation of < 1%.