The objective of this study was to assess the test-retest reliability of an interactive voice response (IVR) version of the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30.Methods
A convenience sample of outpatient cancer clinic patients (n = 127) was asked to complete the IVR version of the QLQ-C30 twice, 2 days apart. The QLQ-C30 is a 30-item, cancer-specific questionnaire composed of single-item and multi-item scales. The instrument has five functional scales (physical, role, cognitive, emotional, and social), three symptom scales (fatigue, pain, and nausea/vomiting), and a global quality-of-life scale. The remaining single items assess dyspnea, appetite loss, insomnia, constipation, diarrhea, and financial problems. The analyses focused on intraclass correlation coefficients (ICCs), comparing the ICC 95 % lower confidence interval (CI) value with a critical value of 0.70.Results
The ICCs for the nine multi-item scales were all above 0.69, ranging from 0.698 to 0.926 (ICC 95 % lower CI value range 0.588-0.895). All of the scales were significantly different from our threshold reliability of 0.70, with the exception of the cognitive functioning scale. The ICCs for the six single items ranged from 0.741 to 0.883 (ICC 95 % lower CI value range 0.646-0.835), and three of the six were statistically different from 0.70. The evidence supports the stability of 11 of the 15 scores obtained on the IVR version of the QLQ-C30 upon repeated measurement.Conclusion
The measurement equivalence of the IVR and paper versions of the QLQ-C30 has been reported elsewhere. This analysis provides evidence demonstrating adequate test-retest reliability of the IVR version for 11 of the QLQ-C30's 15 scores.