Chronic obstructive pulmonary disease (COPD) is a common treatable but incurable lung disease that is characterized by persistent airflow limitation due to the significant exposure to noxious particles or gases resulting in a chronic inflammatory airway response [1]. COPD is strongly linked to a history of smoking and is associated with advanced age [2]. Globally, the World Health Organization estimates that COPD will be the third-leading cause of death in the world by 2030 [3].

Anxiety and depression are two of the most common and least treated comorbidities in individuals with COPD [4] with an estimated prevalence of 10% to 86% [4,5]. In general medical patients, anxiety disorders involve excessive feelings of fear, tension, and worry; changes in behavior such as avoidance or panic attacks; and physical manifestations such as tachycardia and hyperhidrosis [6]. Depressive disorders include emotions of sadness, loss of energy, anhedonia, and feelings of hopelessness, and can cause cognitive and somatic symptoms such as decreased appetite, fatigue, trouble sleeping, and difficulty concentrating [7].

Women and older adults (aged >65 years) with COPD are at an increased risk of developing both anxiety and depression [8,9]. Furthermore, individuals with COPD are 85% more likely to develop anxiety disorders than their healthy age-sex matched controls [10] and patients with other chronic diseases [11]. Anxiety is also reported to cause dyspnea at earlier stages of COPD [12,13], and both disorders are associated with decreased physical functioning and deteriorated health-related quality of life [14,15]. The assessment and timely interventions for these symptoms is essential, as anxiety and depression are associated with increased mortality, COPD exacerbations, hospitalizations [16,17], and medical costs [18].

The Hospital Anxiety and Depression Scale (HADS) is a self-assessment tool developed to measure symptoms of anxiety and depression in clinical settings [19], and is used for individuals with COPD [20,21]. The scale consists of 14 items, with seven items assessing anxiety and seven items assessing depression. Items are rated on a 4-point Likert scale: zero (not present) to 3 (severe symptoms). Scores range from 0 to 21 for each subscale and can be summed to give a total anxiety-depression score with a maximum of 42 points. Higher scores indicate an increasing severity of symptoms, with a cutoff score of 8 indicating high symptoms of depression and anxiety [22].

Several systematic reviews examined the criterion validity of the HADS and reported a wide range of specificity (54%-95%) and sensitivity (44%-100%) values of the HADS in patients with mental disorders [23], impaired physical health [24], cancer [25], cardiac disease [26], multiple sclerosis [27], and COPD [28]. However, the methodological quality and level of evidence for criterion validity [28] and other measurement properties has not been evaluated and critically appraised for individuals with COPD.

We aim to evaluate and critically appraise the validity, reliability, and responsiveness of the HADS in individuals with COPD. Such an evaluation will provide robust measurement information for clinicians and researchers involved in respiratory care and guide the clinical assessment and management of anxiety and depression in individuals with COPD.

The systematic review will be conducted according to the COSMIN (Consensus-based Standards for the Selection of Health Measurement Instruments) guidelines for systematic reviews [29], and the results will be reported following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines [30]. The protocol registration number on PROSPERO is CRD42022302064.

Five systematic databases will be searched for articles investigating the psychometric properties of the HADS. Currently, 12 articles met the inclusion criteria and are included in the systematic review. The results of the psychometric properties of the HADS will be qualitatively summarized and compared against the criteria for good measurement properties. The methodological quality of each selected study will be evaluated using the COSMIN Risk of Bias checklist [29]. The overall quality of evidence will be graded as high, moderate, low, or very low. We expect to complete the systematic review by December 2022.

Anxiety and depression can negatively impact physical functioning, health-related quality of life, and adherence to pulmonary rehabilitation programs in individuals with COPD. This systematic review provides an opportunity to use the HADS as a validated measurement tool for the assessment and treatment of anxiety and depression in individuals with COPD in the clinical setting. This systematic review presents several strengths and limitations. It will be the first systematic review to evaluate and critically appraise the psychometric properties of the HADS in individuals with COPD. Additionally, a comprehensive literature search across five databases will be conducted. The limitations of this review include the possibility of excluding articles written in languages other than English and examining other chronic respiratory disorders.