Development and validation of quality of life scale of nasopharyngeal carcinoma patients: the QOL-NPC (version 2)

Background: The aim was to develop and validate the quality of life scale for nasopharyngeal carcinoma (NPC) patients, the QOL-NPC (version 2), a specific instrument to measure quality of life for NPC patients. Methods: The QOL-NPC was developed and validated according to standard procedures. The patients were assessed using the QOL-NPC, FACT-G, and FACT-H&N. Classical test theory was used to evaluate the reliability, validity, and responsiveness of the QOL-NPC. Results: A total of 487 patients (97.4 %) completed the questionnaire. The QOL-NPC comprised four domains, as follows: physical function (eight items); psychological function (five items); social function (five items); and side effects (eight items). All of the items had a lower proportion of missing data. Cronbach's alpha values of the domains ranged from 0.72 to 0.84. The split-half reliability coefficients ranged from 0.77 to 0.84. All of the intra-class correlation coefficients were > 0.8. The normed fit index, non-normed fit index, and comparative fit index were > 0.89. The root mean square error of approximation was 0.097, with a 90 % confidence interval (0.093, 0.100). The domain scores of the QOL-NPC were significantly correlated with the FACT-G and FACT-H& N (P < 0.05). All of the domain scores of patients using different amounts of radiotherapy were significantly different (P < 0.001). All domain scores decreased at the completion of radiotherapy, with effect sizes ranging from -0.82 to -0.22. Conclusions: The QOL-NPC is valid for measuring QOL with good reliability, validity, and responsiveness. The QOL-NPC is recommended to measure the QOL for Chinese NPC patients.