How to evaluate “Spirometric” lung age – What method is approvable?

Abstract The method predicting lung age was originally proposed by Morris and Temple (1985) . In their method, lung age was estimated by counting back the regression formula predicting normal value of FEV 1 . Since the normal value of FEV 1 at a given age is not unique and exists within a certain range defined as 95% confidence interval, the backward value of lung age calculated with the original method includes statistical and physiological problems. Analyzing the problems related to the original method, we have developed a novel method with revising age-elicited variation in FEV 1 . When the original method is applied, the lung age of a person with measured FEV 1 beyond upper-limit-of-normal (ULN) results in being remarkably young (sometimes, below zero), while that of a person with FEV 1 below lower-limit-of-normal (LLN) is estimated as being very elderly (sometimes, over 100). On the other hand, the novel method, in which age-related variation in FEV 1 is reliably corrected, predicts a wide range of lung age even when measured FEV 1 is significantly above ULN or below LLN.