Psychometric performance of the CushingQoL questionnaire in conditions of real clinical practice.

OBJECTIVE

To evaluate health-related quality of life (HRQoL) in Cushing's syndrome (CS) with the disease-generated CushingQoL questionnaire and to confirm its psychometric properties of test-retest reliability and sensitivity to change.

DESIGN

Clinical practice conditions in a tertiary referral center.

METHODS

The CushingQoL and EuroQoL questionnaires were administered at baseline and during follow-up and correlated with clinical parameters in 59 patients with CS. To check test-retest reliability, stable patients (either biochemically cured or with active hypercortisolism) were evaluated twice. To investigate sensitivity to change, new patients were evaluated at diagnosis and twice more following improvement after successful surgery.

RESULTS

At baseline, patients with active disease scored lower (indicating worse HRQoL) than those cured on the CushingQoL (46 ± 14 vs 58 ± 20, P<0.05) but not on the EuroQoL-visual analog scale (VAS; 64 ± 20 vs 70 ± 16, P NS). Test-retest reliability of CushingQoL was confirmed in stable patients, both in the 'cured group' (intraclass correlation coefficient (ICC)=0.78, n=34) and in the 'active group' (ICC=0.66, n=14). Sensitivity to change was confirmed in the 'improvement group' (n=11), as the CushingQoL score increased 4 ± 1.5 and 9 ± 3 months after surgery (P<0.01 and <0.001 respectively); the EuroQoL-VAS only improved after 9 ± 3 months (P<0.01). Effect sizes were 1.02 and 1.86 for CushingQoL at 4 ± 1.5 and 9 ± 3 months respectively. Finally, scores of both questionnaires were correlated (r=0.504; P<0.001).

CONCLUSIONS

The CushingQoL questionnaire shows good test-retest reliability and sensitivity to change in clinical practice conditions.