Assessment of COPD prevalence

    Borlée, Floor | Universiteit Utrecht IRAS | 22 augustus 2016 | 7.1.16.110CO (3.2.11.022)

The American Thoracic Society (ATS), founded in 1905, tries to improve global health by advancing research, patient care, and public health in pulmonary disease, critical illness, and sleep disorders. The ATS organizes yearly an international conference which provides an ideal opportunity for clinicians and researchers to come together to discuss the latest advances in treatment and care. Each year, nearly 14,000 of these professionals attend the conference. This year the conference was organized in San Francisco between May 13 – May 18 2016.

During this conference I presented my work in the form of a poster (1). Diagnosis of COPD is based on the presence of persistent airflow limitation which is confirmed by post-bronchodilator (BD) spirometry. Nevertheless, epidemiological studies often rely on pre-BD spirometry, self-reports, or medical records. Studies comparing COPD prevalence based on different data sources in the same population found that the definitions used to assess COPD greatly influence prevalence estimates (2-6). We assessed COPD prevalence from a sample of the Dutch general population (20-72 years, n=1,793) based on self-reported data, general practitioners’ Electronic Medical Records (EMR), and post-BD spirometry: using the GLI-2012 lower limit of normal (LLN) (FEV1/FVC below the LLN) and GOLD fixed cut-off (FEV1/FVC <0.70). In addition, we examined the effect of the different COPD definitions on associations with potential risk factors. This study is part of the VGO Study (the Livestock Farming and Neighboring Residents’ Health Study)(7).

We found that COPD prevalence was highest when based on spirometry with the GOLD definition (10.9%), followed by spirometry LLN-definition (5.9%), self-report (4.6%) and EMR (2.9%). Self-reported or EMR-based COPD identified less than 30% of all subjects with COPD based on persistent airflow limitation, which implies that a substantial number of subjects with COPD cannot be identified by self-reports or medical records. This will result in an underestimation of airflow limitation when using self-reported data or EMR data. However, the effect of the different COPD definitions on associations with potential risk factors was limited. The direction of associations between potential risk factors and all four COPD definitions were more or less similar, although the magnitude and statistical significance of the associations varied between the definitions. Results of this study may be informative for population-based epidemiological studies with the aim to evaluate potential risk factors for COPD.

Several studies presented on the ATS also looked into the methodology of COPD assessment. In session A58 ‘Epidemiology of COPD and Lung Cancer’, Tan et al. presented an interesting study about the consistency and reproducibility of COPD prevalence in the general population of Canada based on post-BD measurements (8). They focused especially on the effect of repeated studies on the variability and repeatability of the prevalence estimates for COPD. COPD prevalence was consistent irrespective of the number of sites used (COPD prevalence based on 5 sites: 16.7% and 9 sites: 16.2%) and was reproducible over 9 years for the same sites. This means that repeating the study within a short time frame is probably not necessary for better consistency or reproducibility of COPD prevalence. Aaron et al. presented a study in the same session and analyzed data from COPD prevalence studies to assess the influence of country-level factors on prevalence (9). Country-level factors included demographic, socioeconomic, environmental and geographic factors. Compared to Northern Europe and North America they found a lower COPD prevalence in Australia and New Zealand and the Mediterranean region and higher in Latin America. Sex, age and smoking were confirmed as major determinants of COPD (explained 64% of variability), but 8% of variation in COPD prevalence was explained by country-level factors. 

We found that the burden of COPD in the general population is underestimated when using self-reported data or EMR data. Akinremi et al. presented a poster about undiagnosed airflow limitation prevalence among cardiac patients (10). They found an even higher undiagnosed COPD prevalence. Airflow limitation was defined as FEV1 less than 80% predicted. The prevalence of undiagnosed airflow limitation was 76.6%, of these patients 70% had a moderate limitation and 7.6% severe airflow limitation. To optimize care, there may be need for a routine lung function measurement program among these patients.

References:
1. F. Borlee , J. Yzermans , E. Krop , B. Aalders , J.-P. Zock , C. Van Dijk , K. Maassen , F. Schellevis , D. Heederik , L. A.M. Smit. Assessment Of Asthma And COPD Prevalence: A Comparison Between Three Different Data Sources. Am J Respir Crit Care Med 193;2016:A3694
2. Murgia N, Brisman J, Claesson A, Muzi G, Olin AC, Toren K. Validity of a questionnaire-based diagnosis of chronic obstructive pulmonary disease in a general population-based study. BMC Pulm Med 2014;14:49-2466-14-49.
3. Celli BR, Halbert RJ, Isonaka S, Schau B. Population impact of different definitions of airway obstruction. Eur Respir J 2003;22:268-273.
4. Prieto-Centurion V, Rolle AJ, Au DH, Carson SS, Henderson AG, Lee TA, Lindenauer PK, McBurnie MA, Mularski RA, Naureckas ET, Vollmer WM, Joese BJ, Krishnan JA, CONCERT Consortium. Multicenter study comparing case definitions used to identify patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2014;190:989-995
5. Romanelli AM, Raciti M, Protti MA, Prediletto R, Fornai E, Faustini A. How Reliable Are Current Data for Assessing the Actual Prevalence of Chronic Obstructive Pulmonary Disease? PLoS One 2016;11:e0149302.
6. de Marco R, Marcon A, Rossi A, Anto JM, Cerveri I, Gislason T, Heinrich J, Janson C, Jarvis D, Kuenzli N, Leynaert B, Probst-Hensch N, Svanes C, Wjst M, Burney P. Asthma, COPD and overlap syndrome: a longitudinal study in young European adults. Eur Respir J 2015;46:671-679.
7. Borlee F, Yzermans CJ, van Dijk CE, Heederik D, Smit LA. Increased respiratory symptoms in COPD patients living in the vicinity of livestock farms. Eur Respir J 2015.
8. W.C. Tan, L. Zheng, J.Bourbeau, D.D. Sin, D.E. O’Donnell, F. Maltais, P. Hernandez, K.R.Chapman, D. Marciniuk, J. Road, J. Leipsic, C. Hague, H. Coxson, M. Kirby, J.M. FitzGerald, J.C. Hogg, S.D. Aaron How Consistent and Reproducible Are Prevalence Estimates of COPD in the General Population? Am J of Resp Crit Care Med 193;2016:A2000
9. S.D. Aaron, A.S. Gershon, C. Gao, J. Yang, G.A. Whitmore. Country-Level Effects on COPD Prevalence. Am J of Resp Crit Care Med 193;2016:A2000
10. A.A. Akinremi, K.K. Sobande, K.Hamzat. Prevalence of Undiagnosed Airflow Limitation: Preliminary Report from a Cross Sectional Survey of Cardiac Patients in a Resource-Limited Setting. Am J of Resp Crit Care Med 193;2016:A2005
 

Keyword: COPD prevalence ATS 2016 population-based study post-bronchodilator (BD) spirometry

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