Effect of corrected GLI reference equations on carbon monoxide transfer factor interpretation

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The Carbon monoxide transfer factor (T_LCO) reference equations published by the Global Lung Function Initiative (GLI) in 2017 [1] have a number of advantages compared to previously published equations [2–8], including that they are derived from a large dataset (9710 subjects), use modern equipment, cover a wide age range (5–85 years) obviating the need for separate paediatric and adult equations, and use more sophisticated statistical techniques to account for variation and skewness across the age range. Following the publication of the GLI equations there were a number of studies, such as ours, that examined the impact of changing to the new equations in clinical and research settings [9–12]. Our study [9] analysed a large clinical dataset of adult and paediatric T_LCO results. It showed that adoption of GLI T_LCO reference equations in adults would lead to altered interpretation depending on the equations previously used, with larger effects seen when changing from Crapo [3] and Roca [5] equations, and to a greater extent in adult females. The effect on interpretation in children was less significant.