Validity of the Brazilian version of the COPD assessment test in patients with chronic obstructive pulmonary disease

COPD Assessment Test (CAT) is a questionnaire defined as one of the main options in the assessment of the impact of Chronic Obstructive Pulmonary Disease on patients' life, according to the Global Initiative on Obstructive Lung Diseases. However, the Consensus-based Standards for the Selection of Health Measurement Instruments-COSMIN 2018 has recently determined a correlation coefficient greater than 0.70 and an optimal sample size must have a hundred subjects, hence, validity of the Brazilian version of this instrument is still not yet proven.

To verify the validity of the Brazilian version of the Questionnaire CAT in patients with Chronic Obstructive Pulmonary Disease, comparing it to the Saint George's Respiratory Questionnaire (SGRQ) and correlate it with other outcomes.

Observational transversal study with 101 COPD diagnosed subjects who underwent anthropometric data collection, life habits, CAT and SGRQ questionnaires, modified Medical Research Council (mMRC) dyspnoea scale. Spirometry, six-minute walking test (6MWT) and body mass index, Dyspnoea and exercise capacity (BODE). Each evaluative measure was compared to the total CAT score. The validity was considered for a significant Pearson correlation coefficient (r) greater than 0.7.

It was observed a strong correlation between the total CAT score and the total SGRQ score (r = 0.703; P < 0.001), as well as moderate correlation with mMRC (r = 0.518; P < 0.001). SGRQ Symptoms (r = 0.627; P < 0.001). SGRQ Activity (r = 0.636; P < 0.001) and SGRQ Impact (r = 0.655; P < 0.001). There were similar correlations between CAT and other variables (6MWT, mMRC and BODE) and SGRQ and the same variables.

The CAT questionnaire is a valid, reliable and easy-to-use instrument for assessing symptoms and can record the impact of COPD on the patient's quality of life.