The prevalence of airflow limitation in North-West Russia according to different cut-off values

Background: Chronic obstructive pulmonary disease (COPD) morbidity and mortality is increasing worldwide while its diagnostic criteria and the cut-off defining airflow limitation (AL) are still debatable. Aim: To assess and compare the prevalence of AL in based on two spirometric cut-offs as well as to identify predictors of AL and assess the diagnostic value of respiratory symptoms in adults 35-70 years old in Russia. Methods: The RESearch on the PrEvalence and the diagnosis of COPD and its Tobacco-related aetiology (RESPECT) is a prospective, population-based cohort study. The study population completed questionnaires regarding socio-demographic characteristics, smoking and occupational exposures and respiratory symptoms. Spirometry before and after a bronchodilator (BD) was performed and AL measured by a ratio of FEV1/FVC < 0.7 (fixed cut-off) and < Lower Limit of Normal (LLN). Results: 3133 individuals from 4419 agreed to participate in the study and met the inclusion criteria. Altogether, 2974 and 2388 participants demonstrated satisfactory quality on spirometry before- and after BD test. The overall AL prevalence after BD was 6.8% (95% CI 5.8 – 7.9) by the fixed cut-off and 4.8% (95% CI 3.9 – 5.7) by LLN. The AL prevalence for current smokers after BD test was 12.7% (19.2% for men and 6.2% for women). There was a significant association of AL with tobacco but not with occupational exposure. The positive predictive value for respiratory symptoms for AL by both cut-off values was low. Conclusion: The prevalence of AL in a Russian cohort of adults 35-70 years old in based on two cut-offs is a fairly high. Spirometry is required for a comprehensive COPD diagnosis.