Inter-Day Test-Retest Reproducibility of the CAT, CCQ, HADS and EQ-5D-3L in Patients with Severe and Very Severe COPD

In patients with COPD, the COPD Assessment Test (CAT), Clinical COPD Questionnaire (CCQ), Hospital Anxiety and Depression Scale (HADS) and EuroQol 5D (EQ-5D-3L) are widely used patient reported outcome measures (PROMs) of respiratory symptoms, anxiety, depression and quality of life. Despite established validity, responsiveness and minimal important change (MIC), the reproducibility and especially important agreement parameters remain unreported in these frequently used PROMs. The aim of this study was to investigate the inter-day test-retest reliability and agreement of the CAT, CCQ, HADS and EQ-5D-3L in patients with severe and very severe COPD (FEV1 <50%) eligible for hospital-based pulmonary rehabilitation.

Fifty patients (22 females, mean [SD] age 67 [9] yrs.; FEV₁ 32[9] %; 6-minute walk distance 347 [102] meters; CAT 21 [6] points; BMI: 26 [6] kg/m²) completed the questionnaires (CAT, CCQ, HADS, EQ-5D-3L) in combination with functional performance test instructed by one assessor on test-day one (T1) and by another assessor 7-10 days later on test-day two (T2).

The inter-day test-retest reliability ICC was 0.88 (LL_95CI: 0.80) for CAT; 0.69 (LL_95CI: 0.46) for CCQ; 0.86 (LL_95CI: 0.75) and 0.90 (LL_95CI: 0.82) for HADS-anxiety (A) and depression (D) and 0.87 (LL_95CI: 0.76) for EQ-5D-VAS. The corresponding agreements within a single measurement (standard error of measurement, SEM) and for repeated measurement errors (smallest real difference, SRD) were respectively 2.1 and 2.9 points for CAT; 0.5 and 0.7 points for CCQ total; 1.3 and 1.9 points for HADS-A; 0.9 and 1.3 points for HADS-D and 6.8 and 9.7 VAS-score for EQ-5D-3L, respectively. Ceiling/flooring effect was present in <5% for all questionnaires.

In patients with severe and very severe COPD, the CAT, CCQ, HADS and EQ-5D-3L questionnaires presented moderate to excellent inter-day test-retest reliability, and no floor or ceiling effect was documented for any of the questionnaires. Only CAT and HADS had an acceptable SRD below the established MIC for assessing change over time on group level, and none of the PROMS were fit to assess individual changes over time.