DLCO Biologic Quality-Control Findings From a Multi-Center Global Study

BACKGROUND: The 2017 American Thoracic Society/European Respiratory Society (ATS/ERS) diffusing capacity of the lung for carbon monoxide (DLCO) standards specify a control rule for assessing biologic quality control (BioQC) but have limited guidance on how to establish expected values for control rule variables. This study aimed to determine expected values for DLCO BioQC using coefficient of variation (CV) and compare that the mean +/- 2 SD control rule yields the same precision as mean +/- 12% of the mean. METHODS: DLCO BioQC data were col-lected from a multi-center inhaled medication study. This descriptive study spanned 42 months ending in 2018. The annual DLCO CV was based upon 10 DLCO values separated by at least 5 d. The root mean square CV (RMSCV) was computed for each year and Friedman test evaluated within subject annual CV changes. Ninetieth percentile values were computed for annual control rule limits/mean DLCO. RESULTS: Of 217 BioQCs, the study's first year had 168 subjects with fewer in subsequent years. Annual CV values from RMSCV were 5.3, 4.5, and 4.6% in years 1, 2, and 3, respectively. No change was seen in the CV for those subjects with data for all 3 years, n = 24, P = .07. The 90th percentile of measurements 2 SD/mean DLCO were 15, 12.4, and 11% in years 1, 2, and 3, respectively. CONCLUSIONS: A DLCO BioQC CV <^> 6% is achievable across multiple sites, technologists, and brands of equipment. This CV value assures that meas-urements for control rule variables emerge from an expected range. A control rule of mean +/- 2 SD appeared to yield similar results as the mean +/- 12% of the mean rule reported in the 2017 ATS/ERS DLCO standards.