Population-based case-finding to identify subjects with undiagnosed asthma or COPD

Abstract

Background∼5–10% of adults may have undiagnosed airflow obstruction. The objective of this study was to develop a population-based case-finding strategy to assess the prevalence of undiagnosed airflow obstruction (asthma or COPD) amongst adults with respiratory symptoms in Canada.MethodsAdults without a previous history of asthma, COPD or lung disease were recruited using random digit-dialling and asked if they had symptoms of dyspnoea, cough, sputum or wheeze within the past 6 months. Those who answered affirmatively completed the Asthma Screening Questionnaire (ASQ), COPD-Diagnostic Questionnaire (COPD-DQ) and COPD Assessment Test (CAT). Those with an ASQ score of ≥6 or a COPD-DQ score of ≥20 underwent pre- and post-bronchodilator spirometry to diagnose asthma or COPD.Results12 117 individuals were contacted at home and assessed for study eligibility. Of the 1260 eligible individuals, 910 (72%) enrolled and underwent spirometry. Ultimately, 184 subjects (20% of those enrolled) had obstructive lung disease (73 asthma and 111 COPD). Individuals found to have undiagnosed asthma or COPD had more severe respiratory symptoms and impaired quality of life compared with those without airflow obstruction. The ASQ, COPD-DQ, and CAT had ROC areas for predicting undiagnosed asthma or COPD of 0.49, 0.64 and 0.56, respectively. Four descriptive variables (age, BMI, sex and pack-years smoked) produced better receiver operating characteristic (ROC) values than the questionnaires (ROC area=0.68).Conclusion20% of randomly selected individuals who report respiratory symptoms in Canada have undiagnosed airflow obstruction due to asthma or COPD. Questionnaires could exclude subjects at low risk but lack the ability to accurately find subjects with undiagnosed disease.

Diagnosing asthma and chronic obstructive pulmonary disease

“…For example, the Asthma Screening Questionnaire, a 6-question tool that was found to be accurate for identifying asthma in adults in an initial small study with 50 participants, 22 had a specificity of only 16% upon external validation. 23 Similarly, the widely studied COPD Diagnostic Questionnaire 24 had a specificity of only 34% in a population-based sample. 23 The high false-positive rates associated with these questionnaires render them impractical for use in primary care.…”

Prevalence and burden of obstructive lung disease in the urban poor population of Ottawa, Canada: a community-based mixed-method, observational study

“…Approximately 80% of participants in PROMPT that were diagnosed with an OLD (45-59%) reported no physician-diagnosed lung related disease, suggesting they are unaware of having an OLD. This is 4 times greater than the estimated rate of undiagnosed COPD and asthma in the general population in Canada [13]. Out of the 11 participants interviewed, 3 recognized OLD as a chronic disease they have.…”

“…While many OLDs are preventable and treatable, there is a problematic knowledge gap of undiagnosed OLDs [12,13]. OLDs impose a significant burden on individuals through progressive symptoms, acute pulmonary exacerbations, worsening quality of life, and premature death [12].…”

Finding the true prevalence of obstructive lung disease: two steps forward and one step back

“…The study by PRETEROTI et al [2] from Canada shows how hard this actually is to achieve. In a country with a strong socialised medical system, this group of researchers has boldly attempted to find undiagnosed airway obstruction in a population of metropolitan Canadians from 10 centres.…”

“…Clearly having a comprehensive healthcare system has benefits! PRETEROTI et al [2] have helpfully utilised their sample to look at the accuracy of standard but sparsely evaluated diagnostic and screening questionnaires to identify airflow obstruction and lead to a subsequent diagnosis of asthma or COPD. It is unsurprising that the questionnaires did not fare well and, indeed, by looking at a combination of simple descriptive variables with selected individual items taken from the questionnaires, the investigators were able to produce a more accurate screening tool.…”