To examine the usefulness of a symptom-based case-finding questionnaire (CFQ) and the Medical Research Council (MRC) dyspnea scale in identifying which individuals with known risk factors for chronic obstructive pulmonary disease (COPD) require targeted spirometry in primary care.
Three community primary care practices in Ontario.
Men and women 40 years of age and older with a smoking history of 20 pack-years or more.
Main outcome measures
We administered a CFQ for the presence of cough, sputum, wheeze, dyspnea, and recurrent respiratory infections (possible range of scores from 0 to 5) and applied the MRC dyspnea scale to assess the severity of COPD (possible range of scores from 1 to 5). Spirometric measures of forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were collected, with COPD defined as a postbronchodilator FEV1/FVC of less than 0.7 and FEV1 of less than 80% of the predicted value. Using spirometric data to confirm the diagnosis of COPD, likelihood ratios, pretest and posttest probabilities, and area under a receiver operating characteristic curve were calculated for the total CFQ and MRC scores.
Scores for the CFQ and MRC dyspnea scale were available for 996 and 829 participants, respectively. The likelihood ratios for a total CFQ score of 3 or higher and an MRC dyspnea score of 4 or 5 were 1.82 (95% confidence interval [CI] 1.48 to 2.22) and 4.22 (95% CI 2.08 to 8.56), respectively. The likelihood ratios for a total CFQ score of 2 or less and an MRC dyspnea score of 1 were 0.75 (95% CI 0.66 to 0.85) and 0.50 (95% CI 0.39 to 0.65), respectively. Area under the receiver operating characteristic curve was 0.62 (95% CI 0.58 to 0.67; P < .001) for the total CFQ scores and 0.64 (95% CI 0.60 to 068; P < .001) for the MRC dyspnea scores.
In adults with known risk factors, the likelihood of having moderate to severe COPD is increased in those who report 3 or more common respiratory symptoms and marked functional limitation resulting from dyspnea. However, selecting individuals for spirometry based on symptoms alone will identify less than half of those with moderate to severe COPD.