Levels of immunoglobulin isotypes in serum and respiratory samples of patients with chronic obstructive pulmonary disease: protocol for a systematic review and meta-analysis

INTRODUCTION: Chronic obstructive pulmonary disease (COPD) is an inflammatory respiratory disorder characterised by the progressive worsening of lung function. Acute exacerbation of COPD (AECOPD) is a leading contributor to patient morbidity, mortality and hospitalisations. The clinical significance of immunoglobulin (Ig) levels in COPD patients is not well established and is in need of further investigation. METHODS AND ANALYSIS: We will conduct a systematic review to describe levels of different Ig isotypes (IgG, IgA and IgM) in various samples (serum, sputum and bronchoalveolar lavage) of patients with COPD. IgE levels in COPD patients have been researched and reviewed extensively and hence will be excluded from this review. IgD levels will also be excluded from the review as there is a paucity of data on IgD levels in COPD patients. The primary outcome of interest in this systematic review is assessing Ig isotype levels in patients with COPD. Secondary outcomes that will be assessed include the differences between Ig isotype levels in COPD patients compared with healthy controls, as well as the relationships between Ig isotype levels and key clinical variables, including COPD severity, incidence of AECOPD and AECOPD severity. Embase and Ovid MEDLINE will be used to search for non-randomised studies published from 1946 to October 2022 that report our prespecified primary and secondary outcomes. As per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol, retrieved studies will undergo a two-phase screening process conducted by two independent reviewers. Prespecified primary and secondary outcomes will be extracted from eligible studies, and descriptive statistics will be used to analyse extracted outcomes. The risk of bias will be assessed using the Risk Of Bias In Non-randomised Studies - of Interventions (ROBINS-I) tool. ETHICS AND DISSEMINATION: Ethics approval is not required as this is a protocol for a systematic review and meta-analysis. Findings will be disseminated through peer-reviewed publications and other formats including conference presentations. PROSPERO REGISTRATION NUMBER: CRD42020192220.