Age- and height-based prediction bias in spirometry reference equations

Abstract

Prediction bias in spirometry reference equations can arise from combining equations for different age groups, rounding age or height to integers or using self-reported height.To assess the bias arising from these sources, the fit of 13 prediction equations was tested against the Global Lungs Initiative (GLI) dataset using spirometric data from 55,136 healthy Caucasians (54% female). The effects on predicted values of using whole-year age versus decimal age, and of a 1% bias in height, were quantified.In children, the prediction bias relative to GLI ranged from -22% to +17%. Switching equations at 18 yrs of age led to biases of between -846 (-14%) and +1,309 (+38%) mL. Using age in whole years rather than decimal age introduced biases from -8% to +7%, whereas a 1% overestimation of height introduced bias that ranged from +1% to +40%. Bias was greatest in children and adolescents, and in short elderly subjects.Using a single spirometry equation applicable across all ages and populations reduces prediction bias. Measuring and recording age and height accurately are also essential if bias is to be minimised.

Lung function after preterm birth: development from mid-childhood to adulthood

“…Finally, and contrary to some previous studies, 10 11 the all-age reference equation provided by Stanojevic et al 17 allowed for uniform handling of data from childhood to adulthood. 19 The equation fitted the control population well with two exceptions: for FEF and FEV 1 /FVC measured at 18 years of age in the 1982-1985 cohort, the 95% CIs did not include zero. The prime objective of this study was to include all EP-born neonates (ie, at gestational age ≤28 weeks).…”

“…Larger longitudinal studies across decades are necessary to unravel these issues and these are logistically demanding to carry out, illustrated by a paucity of studies and the high dropout rates in some of them. A complicating and relevant factor is that pubertal lung function development is difficult to modulate mathematically, as illustrated by Quanjer et al 19 Thus, to avoid being misled, high quality reference equations are critical and comparable subjects 'unexposed' to preterm birth should be studied in parallel.…”

Implications of the Transition From Zapletal to GLI Reference Values for Spirometry

“…5 Furthermore, the algorithm published by Zapletal was based on a small data set of 60 boys and 51 girls, whereas the GLI values have been based on measurements in 77 658 healthy nonsmokers from around the world, of which 15 264 persons were girls and 15 601 were boys between 2.5 and 18 years old. 7 These aspects explain why use of Zapletal versus GLI reference data sets yields these differing results.…”

Paediatric spirometry guideline of the South African Thoracic Society: Part 1

“…[15] Height should be measured to 0.1 cm accuracy, using a stadiometer for each patient. [16] If standing height cannot be measured -e.g. in patients with severe spinal or thoracic cage abnormalities -the arm span may be used as an estimate of height.…”

“…This lack of continuity across ages has been addressed in the new equations published through the GLI. [16] These equations use large numbers of participants from 33 countries across the whole age range (3 -95 years) and use of up-to-date methods. The equation is limited by the fact that it currently does not include data from Southern African populations; however, it is currently the most robustly developed equation with continuity across ages.…”