TY - JOUR T1 - Internal consistency of reference equations JF - European Respiratory Journal JO - Eur Respir J SP - 233 LP - 234 DO - 10.1183/09031936.00022411 VL - 38 IS - 1 AU - S. Verbanck AU - J. Vandevoorde AU - W. Vincken Y1 - 2011/07/01 UR - http://erj.ersjournals.com/content/38/1/233.abstract N2 - To the Editors:In a recent European Respiratory Journal paper addressing the choice of reference values for spirometric indices, mean z-scores were used to quantify deviation from a large collated data set or to establish the absence of secular trends in forced expiratory volume in 1 s (FEV1) or forced vital capacity (FVC) [1]. Yet, once an appropriate set of reference equations is selected for use in any given laboratory, it is equally important to assess whether these equations are internally consistent, e.g., in terms of age dependency of the various parameters under study. When consulting the most recent standardisation documents for guidance on the choice of reference equations [2, 3] the American Thoracic Society (ATS)/European Respiratory Society (ERS) Task Force literally states “currently this committee does not recommend any specific set of equations for use in Europe”. Due to our laboratory’s particular geographical location, we have thus far felt compelled to apply the European … ER -