Variations in FVC and FEV1 Biologic Quality Control Measures in a Global Multi-Center Clinical Trial

BACKGROUNDAlthough quality control standards are recommended to ensure accurate test results, the coefficient of variation for the FVC and FEV1 biologic quality control (BioQC) is not specified. The primary aim of this study was to evaluate variations in spirometry BioQCs in a large and diverse cohort of individuals to determine an acceptable standard for the coefficient of variation. METHODSThe FVC and FEV1 biologic control data were secondary analyses from an inhaled medication trial that was conducted over 3 y ending in 2018 that included 114 laboratories. Results were sent to a central repository for expert review. The FVC and FEV1 coefficients of variation were based upon a minimum of 10 spirometry values annually separated by at least 5 d. A second method of computing the coefficient of variation used 10 values within 28 d. Descriptive statistics were computed. Wilcoxon signed-rank tests were conducted to compare whether the median coefficient of variation values between the 2 methods differed, tested at α = 0.05 using SPSS. RESULTSOf 249 biologic control participants, 170 met the first year's inclusion criteria. The coefficient of variation for the 5-d separated method was < 5% for 94.1% of FVC and 93.5% of FEV1 values in the first year. By year 3, 90% of FVC and FEV1 coefficient of variation values were < 4%. The medians for the 5-d separated and the 28-d measure showed no difference for either FVC coefficient of variation or FEV1 coefficient of variation, Z = -1.764, P = .78, and Z = -0.980, P = .33, respectively. CONCLUSIONSInterlab biologic control variation values of < 4% for FVC and FEV1 are achievable; however, individual labs should strive to attain lower values. Acceptable coefficients of variation can be achieved within 28 d.