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Underestimation of airflow obstruction among young adults using FEV1/FVC<70% as a fixed cut-off: a longitudinal evaluation of clinical and functional outcomes.
  1. Isa Cerveri (icerveri{at}smatteo.pv.it)
  1. Division of Respiratory Diseases, IRCCS "San Matteo" Hospital Foundation, University of Pavia, Italy
    1. Angelo G. Corsico (angelo.corsico{at}unipv.it)
    1. Division of Respiratory Diseases, IRCCS "San Matteo" Hospital Foundation, University of Pavia, Italy
      1. Simone Accordini
      1. Unit of Epidemiology and Medical Statistics, University of Verona, Italy
        1. Rosanna Niniano
        1. Division of Respiratory Diseases, IRCCS "San Matteo" Hospital Foundation, University of Pavia, Italy
          1. Elena Ansaldo
          1. Division of Respiratory Diseases, IRCCS "San Matteo" Hospital Foundation, University of Pavia, Italy
            1. Josep M. Antó
            1. CREAL at Institut Municipal d'Investigació Mèdica (IMIM), Barcelona, Spain
              1. Nino Künzli
              1. CREAL at Institut Municipal d'Investigació Mèdica (IMIM), Barcelona, Spain
                1. Christer Janson
                1. Department of Medical Sciences, Respiratory Medicine and Allergology, University of Uppsala, Sweden
                  1. Jordi Sunyer
                  1. CREAL at Institut Municipal d'Investigació Mèdica (IMIM), Barcelona, Spain
                    1. Deborah Jarvis
                    1. Respiratory Epidemiology and Public Health Group, NHLI, Imperial College, London, United Kingdom
                      1. Cecilie Svanes
                      1. Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway
                        1. Thorarinn Gislason
                        1. Dep. of Allergy, Respiratory Medicine and Sleep, Landspitali University Hospital, Reykjavik, Iceland
                          1. Joachim Heinrich
                          1. Inst. of Epidemiology, GSF-National Research Center for Environment and Health, Neuherberg, Germany
                            1. Jan P. Schouten
                            1. Dep. of Epidemiology, University Medical Center Groningen, University of Groningen, Netherlands
                              1. Matthias Wjst
                              1. Inst. of Epidemiology, GSF-National Research Center for Environment and Health, Neuherberg, Germany
                                1. Peter Burney
                                1. Respiratory Epidemiology and Public Health Group, NHLI, Imperial College, London, United Kingdom
                                  1. Roberto de Marco
                                  1. Unit of Epidemiology and Medical Statistics, University of Verona, Italy

                                    Abstract

                                    Background: Early detection of airflow obstruction is particularly important among young adults because they are more likely to benefit from intervention. Using the FEV1/FVC<70% fixed ratio, airflow obstruction may be under-diagnosed. The lower limit of normal (LLN) which is statistically defined by the lower 5th percentile of a reference population, is physiologically appropriate but it still needs a clinical validation.

                                    Methods: To evaluate the characteristics and longitudinal outcomes of subjects misidentified as normal by the fixed ratio with respect to the LLN, 6,249 participants (aged 20-44 years) in the European Community Respiratory Health Survey (ECRHS) were examined and classified into 3 groups (absence of airflow obstruction by the LLN and the fixed ratio; presence of airflow obstruction only by the LLN; presence of airflow obstruction by the two criteria) in 1991-93. LLN equations were obtained from the normal non-smoking participants. A set of clinical and functional outcomes was evaluated in 1999-2002.

                                    Results: The misidentified subjects were 318 (5.1%); only 45.6% of the subjects with airflow obstruction by the LLN were also identified by the fixed cut-off. At baseline, FEV1 (107%, 97%, 85%) progressively decreased and bronchial hyperresponsiveness (slope 7.84, 6.32, 5.57) progressively increased across the 3 groups. During the follow-up, misidentified subjects had a significantly higher risk of developing COPD and a significantly higher use of health resources (medicines, ED visits/hospital admissions) because of breathing problems than the subjects without airflow obstruction (p<0.001).

                                    Conclusions: Our findings show the importance of using statistically derived spirometric criteria to identify airflow obstruction.

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