Development and evaluation of a Korean version of a thyroid-specific quality-of-life questionnaire scale in thyroid cancer patients

Abstract

Purpose The purpose of this study was to develop a Korean version of the self-reported thyroid-specific quality of life (QoL) questionnaire for thyroid cancer patients (KT-QoL), and to evaluate its reliability and validity. Materials and Methods Two hundred seventy-two patients who underwent thyroidectomy from January to December 2010 were recruited in this study. The original version of the thyroid QoL was translated into Korean and evaluated for its reliability and validity. Using the developed KT-QoL, the postoperative QoL was evaluated until postoperative 1 year. Results At the preoperative baseline, the item internal consistency (IIC) ranged from -0.19 to 0.76, with low IIC values for items 2, 17, and 27. Item discriminant validity ranged from 86% to 97%. These values were similar at the postoperative periods. The internal consistency reliability (Cronbach's α) was high for all dimensions, ranging from 0.90 to 0.95. The test-retest reliability (intraclass correlation coefficient) was acceptable (0.74-0.82). The external validity examined by the correlation between the item 1j (voice changes) of KT-QoL and the voice handicap index-30 ranged from 0.51 to 0.75. Patients' QoL scores decreased after surgery, which demonstrated the sensitivity of the questionnaire. The QoL scores in patients with lobectomy showed best QoL scores postoperatively and those with receiving radioactive iodine still showed decreased QoL scores along the postoperative periods. Conclusion These results demonstrate that KT-QoL is a valid instrument for evaluating QoL of Korean patients with thyroid cancer.