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Understanding how Spirometry Interpretation May Influence Decision Making and Disease Misclassification. Management of Asthma and COPD A Critical Appraisal Approach. Anthony D. D’Urzo MD, MSc , CCFP, FCFP Associate Professor, Department of Family and Community Medicine
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Understanding how Spirometry Interpretation May Influence Decision Making and Disease Misclassification Management of Asthma and COPDA Critical Appraisal Approach Anthony D. D’Urzo MD, MSc, CCFP, FCFP Associate Professor, Department of Family and Community Medicine University of Toronto Chair, Primary Care Respiratory Alliance of Canada (PCRC) Director, Primary Care Lung Clinic, Toronto www.lungclinic.ca
Management of Asthma and COPDA Critical Appraisal ApproachUnderstanding how Spirometry Interpretation May Influence Decision Making and Disease Misclassification Pieter Jugovic MD, MSc, CCFP Assistant Professor, Department of Family and Community Medicine University of Toronto Member , Primary Care Respiratory Alliance of Canada (PCRC)
Disclosure Anthony D. D’Urzo :None Pieter Jugovic: None
Management of Asthma and COPDA Critical Appraisal Approach Objectives • Use critical appraisal strategies to evaluate limitations of a spirometry interpretation algorithm currently endorsed by the Ontario Thoracic Society (OTS). * • present a new spirometry interpretation algorithm that is in keeping with current guidelines for asthma and COPD management. * Spirometry in Primary Care (CD-ROM), Ontario Lung Association 2008.
Differentiating Asthma from COPD • Why is this important?
Differentiating Asthma from COPD • First Line Therapy • Asthma - Inhaled glucocorticosteroids • COPD - Inhaled bronchodilator therapy – long acting for maintenance: ↓ hyperinflation ↑ inspiratory capacity IMPORTANT • Long-acting-β2-agonist monotherapy contraindicated in ASTHMA
Role of Spirometry in COPD DiagnosisCOPD Diagnosis Confirmed by Spirometry “Airflow Obstruction” Consistent reduction in the ratio of FEV1/FVC < 0.70 or LLN* * LLN = lower limit of normal FEV1 = Forced expiratory volume in one second FVC = Forced vital capacity O’Donnell DE et al. CTS Recommendations for Management of COPD. 2008 Update Highlights for Primary Care. Can Resp J 2008; 15(SupplA): 1A-8A
Role of Spirometry in Asthma Diagnosis Increased FEV1 by 12 % or 200 cc after B2-agonist challenge* FEV1/FVC not formerly included in diagnostic decision making *CMAJ 1999; 161: 51-61.
FEV1: Maximal volume of air exhaled after a maximal inhalation in the first second of a forced exhalationFVC: Maximal volume of air exhaled after inhalation during a forced exhalation* FVC < 80 predicted = full pulmonary function tests (PFTs) to rule out hyperinflation vs. combined obstructive and restrictive defect** FVC > 80% predicted***FEV1 and FVC < 80% predicted****The % change is calculated as Postbronchodilator FEV1 – Prebronchodilator FEV1 divided by the Prebronchodilator FEV1. FEV1 may not improve after β2-agonist challenge.*****Lack of change in FEV1 is non-diagnostic; referral for Methacholine challenge recommended. Can Fam Physician, in press
Spirometry Interpretation Can Fam Physician (in Press)
Spirometry Interpretation Can Fam Physician (in Press)
Spirometry Interpretation Can Fam Physician (in Press)
Spirometry Interpretation Can Fam Physician (in Press)
Management of Asthma and COPDA Critical Appraisal Approach Summary/Conclusion • there is considerable spirometric overlap between asthma and COPD • spirometric overlap may lead to disease misclassification • the OTS endorsed spirometry interpretation algorithm is difficult to use as a stand alone doccument • the OTS endorsed spirometry interpretation algorithm lacks a logic string leading to a post-bronchodilator (PD) FEV1/FVC ratio: an omission which hinders COPD diagnosis.
Management of Asthma and COPDA Critical Appraisal Approach Summary/Conclusion • the OTS endorsed spirometry interpretation algorithm uses PD changes in FEV1 to distinguish between asthma and COPD; a strategy that could lead to disease misclassification • the OTS endorsed spirometry interpretation algorithm did not suggest bronchodilator challenge if the FEV1/FVC was > 0.70; a strategy which could result in under diagnosis of asthma