Criteria
Global Initiative for Chronic Obstructive Lung Disease grades and severity of airflow obstruction in COPD (based on postbronchodilator forced expiratory volume in the first second of expiration [FEV1])[1]
In pulmonary function testing, a nonfully reversible airflow obstruction (i.e., postbronchodilator) FEV1/forced vital capacity (FVC) ratio of <0.70 is commonly considered diagnostic for COPD. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) system categorizes airflow limitation into stages.
In patients with FEV1/FVC <0.70:
GOLD 1 - mild: FEV1 ≥80% predicted
GOLD 2 - moderate: 50% ≤ FEV1 <80% predicted
GOLD 3 - severe: 30% ≤ FEV1 <50% predicted
GOLD 4 - very severe: FEV1 <30% predicted.
The GOLD guideline uses a combined COPD assessment approach to group patients according to symptoms and previous history of exacerbations. Symptoms are assessed using the Modified British Medical Research Council (mMRC) or COPD assessment test (CAT) scale. GOLD cautions against the use of the mMRC dyspnea scale alone for assessing patients, as symptoms of COPD go beyond dyspnea alone. For this reason, the CAT is preferred. However, GOLD acknowledges that the use of the mMRC scale is widespread, and so a threshold of an mMRC grade ≥2 is still included to define "more breathless" patients in its assessment criteria.[1]
Group A: low risk (0-1 exacerbation per year, not requiring hospitalization) and fewer symptoms (mMRC 0-1 or CAT <10)
Group B: low risk (0-1 exacerbation per year, not requiring hospitalization) and more symptoms (mMRC ≥2 or CAT ≥10)
Group C: high risk (≥2 exacerbations per year, or one or more requiring hospitalization) and fewer symptoms (mMRC 0-1 or CAT <10)
Group D: high risk (≥2 exacerbations per year, or one or more requiring hospitalization) and more symptoms (mMRC ≥2 or CAT ≥10).
In the 2023 GOLD report, GOLD proposed a further evolution of the criteria, merging groups C and D into a single group “E” to reflect the clinical relevance of exacerbations, independent of the level of symptoms of the patient. This proposal has yet to be validated by clinical research.[1]
GOLD classification of exacerbation severity:[1]
Exacerbations are graded in severity after the event has occurred
Mild: required treatment with short-acting bronchodilators only
Moderate: required treatment with short-acting bronchodilators and oral corticosteroids, and possibly antibiotics too
Severe: patient required hospital admission or visit to the emergency department. Acute respiratory failure may also have occured.
GOLD classification of severity in hospitalized patients with acute exacerbations of COPD:[1]
No respiratory failure
Respiratory rate ≤24 breaths/minute
Heart rate <95 beats/minute
No use of accessory muscles of respiration
No changes in mental status
Hypoxemia improves when supplemental oxygen is given via Venturi mask at 24% to 35% inspired oxygen (FiO2)
Partial pressure of carbon dioxide (PaCO2) is not increased.
Acute respiratory failure - nonlife-threatening
Respiratory rate >24 breaths/minute
Using accessory muscles of respiration
No changes in mental status
Hypoxemia improves when supplemental oxygen is given via Venturi mask at >35% FiO2
Hypercarbia occurs: PaCO2 is increased relative to baseline or is elevated (50 mmHg-60 mmHg).
Acute respiratory failure - life-threatening
Respiratory rate >24 breaths/minute
Using accessory muscles of respiration
Acute changes in mental status
Hypoxemia does not improve when supplemental oxygen is given via Venturi mask, or FiO2 >40% is required
Hypercarbia occurs: PaCO2 is increased relative to baseline or is elevated (>60 mmHg), or acidosis is present (pH ≤7.25).
Pre-COPD’ and Preserved Ratio Impaired Spirometry (PRISm)
Some patients are symptomatic, have structural abnormalities such as emphysema, or have signs typically associated with COPD including low FEV₁, hyperinflation, reduced lung diffusing capacity or rapid reduction in FEV₁, but do not demonstrate postbronchodilator airflow obstruction (i.e. FEV₁/FVC ≥0.7). These patients may eventually develop airflow obstruction, but some do not.[1]
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