The assertion by Dr Thiadens and colleagues¹ that identification of airflow limitation and estimation of its reversibility by a bronchodilator is less reliable when measured by peak expiratory flow (PEF) than by forced expiratory volume in one second (FEV₁) cannot be allowed to go unchallenged. They measured both values with a Microlab 3300 turbine spirometer, disregarding the fact that, in primary care, PEF is almost always measured by peak flow meters of variable orifice type which employ an entirely different principle and give considerably higher values. Jones and Mullee,² who compared a similar Microlab turbine spirometer with a mini-Wright meter, found that values of PEF measured by the latter were, on average, 87 l/min higher. Hence, the values reported by Thiadens et al would have been much higher if they had been measured with a peak flow meter.

To compare the reliability of PEF and FEV₁ for estimating magnitude of airflow . . . [Full text of this article]