Management of Asthma and COPD A Critical Appraisal Approach

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Management of Asthma and COPDA Critical
Appraisal Approach
Understanding how Spirometry Interpretation May
Influence Decision Making and Disease
Misclassification

• Anthony D. DUrzo 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

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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)

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Disclosure

• Anthony D. DUrzo None
• Pieter Jugovic None

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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.

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Differentiating Asthma from COPD

• Why is this important?

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Differentiating Asthma from COPD

• First Line Therapy
• Asthma - Inhaled glucocorticosteroids
• COPD - Inhaled bronchodilator therapy long
  acting for maintenance ? hyperinflation
  ? inspiratory capacity
• IMPORTANT
• Long-acting-ß2-agonist monotherapy
  contraindicated in ASTHMA

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Differentiating Asthma from COPD
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Role of Spirometry in COPD DiagnosisCOPD
Diagnosis Confirmed by Spirometry Airflow
Obstruction
Consistent reduction in the ratio of FEV1/FVC
lt 0.70 or LLN LLN lower limit of normal
FEV1 Forced expiratory volume in one second
FVC Forced vital capacity
ODonnell DE et al. CTS Recommendations for
Management of COPD. 2008 Update Highlights for
Primary Care. Can Resp J 2008 15(SupplA) 1A-8A
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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.

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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 lt 80 predicted full pulmonary
function tests (PFTs) to rule out hyperinflation
vs. combined obstructive and restrictive
defect FVC gt 80 predictedFEV1 and FVC lt
80 predictedThe change is calculated as
Postbronchodilator FEV1 Prebronchodilator FEV1
divided by the Prebronchodilator FEV1. FEV1 may
not improve after ß2-agonist challenge.Lack
of change in FEV1 is non-diagnostic referral for
Methacholine challenge recommended.
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Spirometry Interpretation
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Spirometry Interpretation
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Spirometry Interpretation
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Spirometry Interpretation
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Spirometry Interpretation
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Spirometry Interpretation
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Spirometry Interpretation
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Spirometry Interpretation
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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.

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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 gt 0.70 a strategy
  which could result in under diagnosis of asthma