Validation of the Tuebingen CD-25 Inventory as a Measure of Postoperative Health-Related Quality of Life in Patients Treated for Cushing's Disease

Abstract

Background: To evaluate the construct and criterion validity of the Tuebingen Cushing's disease quality of life inventory (Tuebingen CD-25) for application in patients treated for Cushing's disease (CD).

Methods: A total of 176 patients with adrenocorticotropin hormone-dependent CD (144 of them female, overall mean age 46.1 ± 13.7 years) treated at 3 large tertiary referral centers in Germany were studied. Construct validity was assessed by hypothesis testing (self-perceived symptom reduction assessment) and contrasted groups (patients with vs. without hypercorticolism). For this purpose, already existing data from 55 CD patients was used, representing the hypercortisolemic group. Criterion validity (concurrent validity) was assessed in relation to the Cushing's quality of life questionnaire (CushingQoL), the Short Form 36 health survey (SF-36), and the body mass index (BMI).

Results: Patients with self-perceived remarkable symptom reduction had significant lower Tuebingen CD-25 scores (i.e. better health-related quality of life) than patients with self-perceived insufficient symptom reduction (p < 0.05). Similarly, the mean scores of the Tuebingen CD-25 scales were lower in patients without hypercortisolism (total score 27.0 ± 17.2) compared to those with hypercortisolism (total score 45.3 ± 22.1; each p < 0.05), providing evidence for construct validity. Criterion validity was confirmed by the correlations between the Tuebingen CD-25 total score and the CushingQoL (Spearman's coefficient -0.733), as well as all scales of the SF-36 (Spearman's coefficient between -0.447 and -0.700).

Conclusion: The analyses presented in this large-sample study provide robust evidence for the construct and criterion validity of the Tuebingen CD-25.