PT  - JOURNAL ARTICLE
AU  - Kate M. Johnson
AU  - Stirling Bryan
AU  - Shahzad Ghanbarian
AU  - Don D. Sin
AU  - Mohsen Sadatsafavi
TI  - Characterising undiagnosed chronic obstructive pulmonary disease: a systematic review and meta-analysis
AID  - 10.1101/184986
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 184986
4099  - http://biorxiv.org/content/early/2017/09/07/184986.short
4100  - http://biorxiv.org/content/early/2017/09/07/184986.full
AB  - Background A significant proportion of patients with chronic obstructive pulmonary disease (COPD) remain undiagnosed. Characterising these patients can increase our understanding of the ‘hidden’ burden of COPD and the effectiveness of case detection interventions.Methods We conducted a systematic review and meta-analysis to compare patient and disease risk factors between patients with undiagnosed persistent airflow limitation and those with diagnosed COPD. We searched MEDLINE and EMBASE for observational studies of adult patients meeting accepted spirometric definitions of COPD. We extracted and pooled summary data on the proportion or mean of each risk factor among diagnosed and undiagnosed patients (unadjusted analysis), and coefficients for the adjusted association between risk factors and diagnosis status (adjusted analysis). This protocol is registered with PROSPERO (CRD42017058235).Findings 2,083 records were identified through database searching and 16 articles were used in the meta-analyses. Diagnosed patients were less likely to have mild (v. moderate to very severe) COPD (odds ratio [OR] 0·30, 95% CI 0·24-0·37, 6 studies) in unadjusted analysis. This association remained significant but its strength was attenuated in the adjusted analysis (OR 0·72, 95% CI 0·58-0·89, 2 studies). Diagnosed patients were more likely to report respiratory symptoms such as wheezing (OR 3·51, 95% CI 2·19-5·63, 3 studies) and phlegm (OR 2·16, 95% CI 1·38-3·38, 3 studies), had more severe dyspnoea (modified Medical Research Council scale mean difference 0·52, 95% CI 0·40-0·64, 3 studies) and slightly greater smoking history than undiagnosed patients. Patient age, sex, current smoking status, and the presence of coughing were not associated with a previous diagnosis.Interpretation Patients with undiagnosed persistent airflow limitation had less severe airflow obstruction and fewer respiratory symptoms than diagnosed patients. This indicates that there is lower disease burden among undiagnosed patients compared to those with diagnosed COPD, which may significantly delay the diagnosis of COPD.Funding Canadian Institutes of Health Research.Declaration of interests We declare no competing interests.Author Contributions MS, SB, and KJ formulated the study idea and designed the study. KJ and SG performed all data analyses and MS, SB and DS contributed to interpretation of findings. KJ wrote the first draft of the manuscript. All authors critically commented on the manuscript and approved the final version. MS is the guarantor of the manuscript.