Comparison of face-to-face interview and telephone interview administration of COPD assessment test: a randomized study

Objective To assess the measurement properties of the COPD assessment test (CAT) in a randomized trial comparing a face-to-face interview (FFI) with a telephone interview (TI). Methods A randomized study was conducted at two teaching hospitals in Fortaleza, Brazil. Patients were randomly assigned to answer the CAT questionnaire either in a FFI or by TI. The two groups were assessed for internal consistency reliability, cross-sectional validity and test-retest reliability. All patients performed spirometry and answered the modified medical research council dyspnea scale and the St. George's respiratory questionnaire (SGRQ). Results The total scores of the CAT questionnaire were similar for face-to-face and TI groups, 20.71 (95 % CI 18–23.4) versus 20.81 (95 % CI 19.31–21.7), respectively. For both mode of administration, we found good internal consistency reliability, the Cronbach's alpha ranged from 0.74 (95 % CI 0.61–0.84) to 0.89 (95 % CI 0.84–0.93) for the TI and FFI, respectively. In general, moderate-to-high correlations of CAT with SGRQ were observed, independent of the administration format. For the test–retest reliability, the intraclass correlation coefficients were very similar for both FFI and TI group 0.96 (95 % CI 0.93–0.97) versus 0.98 (95 % CI 0.96–0.98), respectively. Conclusion This study demonstrated that the CAT questionnaire administration either in a FFI or by TI presents moderate-to-high measurement properties. This provides support for the use of both modes of questionnaire administration.