The COPD assessment test: a systematic review

Area of Science:

• Pulmonary Medicine
• Health Outcomes Research
• Psychometrics

Background:

• The COPD assessment test (CAT) is a widely used self-administered questionnaire for assessing health-related quality of life in individuals with chronic obstructive pulmonary disease (COPD).
• Evaluating the psychometric properties of the CAT is crucial for its accurate interpretation and application in clinical practice and research.

Purpose of the Study:

• To systematically review and evaluate the existing literature on the reliability, validity, responsiveness, and minimum clinically important difference (MCID) of the COPD assessment test (CAT) in adults with COPD.

Main Methods:

• A comprehensive literature search was conducted across multiple databases for studies assessing the psychometric properties of the CAT.
• Two independent reviewers screened studies, extracted data, and assessed methodological quality using the COSMIN checklist.
• Included studies analyzed reliability (internal consistency, test-retest) and validity (convergent, longitudinal) against established measures.

Main Results:

• Thirty-six studies involving 45 to 6469 participants were included. The CAT demonstrated strong internal consistency (0.85-0.98) and test-retest reliability (0.80-0.96).
• Convergent and longitudinal validity were supported by correlations with SGRQ-C, CCQ, and mMRC. CAT scores effectively differentiated between GOLD stages, exacerbation status, and mMRC grades.
• The CAT showed responsiveness to pulmonary rehabilitation (mean decrease of 2.2-3 units) and exacerbations (mean increase of 4.7 units). A single study reported MCID values of 2 units (anchor-based) and 3.3-3.8 units (distribution-based).

Conclusions:

• The reviewed literature supports the reliability and validity of the COPD assessment test (CAT) for measuring quality of life in COPD patients.
• The CAT is a responsive tool, reflecting changes associated with interventions like pulmonary rehabilitation and clinical events such as exacerbations.
• While the CAT exhibits strong psychometric properties, the determination of its minimum clinically important difference (MCID) requires further robust investigation.