Reliability of 95% confidence interval revealed by expected quality-of-life scores: an example of nasopharyngeal carcinoma patients after radiotherapy using EORTC QLQ-C 30

Health and Quality of Life Outcomes

Research

Wen-Chung Wang¹  Wen-Pin Lai²  Tsair-Wei Chien³  Agnes LF Chan⁴  Henry WC Leung⁵  Shun-Jin Lin⁶ 

[1] Assessment Research Center, The Hong Kong Institute of Education, Tai Po, Hong Kong, China;Department of Emergency, Chi-Mei Medical Center, Tainan, Taiwan;Department of Pharmacy, Chi-Mei Medical Center, Tainan, Taiwan;Department of Hospital and Health Care Administration, Chia-Nan University of Pharmacy and Science, Tainan, Taiwan;Department of Pharmacy, Chi-Mei Medical Center, Tainan, Taiwan;School of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan;Department of Radiation Oncology, Taipei Medical University, Shuang Ho Hospital, Taipei, Taiwan;School of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan;

关键词: Item Response Theory;    Item Difficulty;    Classic Test Theory;    Response Score;    Skewness Coefficient;   

DOI  :  10.1186/1477-7525-8-68

 received in 2010-01-12, accepted in 2010-07-13,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundMany researchers use observed questionnaire scores to evaluate score reliability and to make conclusions and inferences regarding quality-of-life outcomes. The amount of false alarms from medical diagnoses that would be avoided if observed scores were substituted with expected scores is interesting, and understanding these differences is important for the care of cancer patients. Using expected scores to estimate the reliability of 95% confidence intervals (CIs) is rarely reported in published papers. We investigated the reliability of patient responses to a quality-of-life questionnaire and made recommendations for future studies of the quality of life of patients.MethodsA total of 115 patients completed the EORTC core questionnaire QLQ-C30 (version 3) after radiotherapy. The observed response scores, assumed to be one-dimensional, were summed and transformed into expected scores using the Rasch rating scale model with WINSTEPS software. A series of simulations was performed using a unified bootstrap procedure after manipulating scenarios with different questionnaire lengths and patient numbers to estimate the reliability at 95% confidence intervals. Skewness analyses of the 95% CIs were compared to detect different effects between groups according to the two data sets of observed and expected response scores.ResultsWe found that (1) it is necessary to report CIs for reliability and skewness coefficients in papers; (2) data derived from expected response scores are preferable to making inferences; and (3) visual representations displaying the 95% CIs of skewness values applied to item-by-item analyses can provide a useful interpretation of quality-of-life outcomes.ConclusionReliability coefficients can be reported with 95% CIs by statistical software to evaluate the internal consistency of respondent scores on questionnaire items. The SPSS syntax procedures for estimating the reliability of the 95% CI, expected score generation and visual skewness analyses are demonstrated in this study. We recommend that effect sizes such as a 95% CI be reported along with p values reporting significant differences in quality-of-life studies.

【 授权许可】

Unknown   
© Chien et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.