title: Validity and reliability of EQ-5D-3L for breast cancer patients in Korea.
abstract: BACKGROUND
  Recently, breast cancer incidence and prevalence has been increasing. Patients' health related quality of life is important considerations in the treatment of breast cancer. The EQ-5D-3L is one of most popular instruments to measure health related quality of life. This study was aimed to evaluate the validity and reliability of EQ-5D-3L in post-operative breast cancer patients from Korea.
  
  
  METHODS
  A total of 827 patients visiting the ambulatory cancer center of 1 tertiary hospital after breast cancer surgery self-administered the EQ-5D-3L and Functional Assessment of Cancer Therapy-Breast Cancer (FACT-B). We evaluated known-group validity using differences in the EQ-5D-3L index and EQ-VAS score according to demographic and clinical data. The discriminatory ability of the EQ-5D-3L was determined by comparing the mean FACT-B subscale scores between subjects with no problems and subjects with moderate or severe problems in each EQ-5D-3L dimension. Construct validity was evaluated by Pearson correlation coefficients among the EQ-5D-3L index and FACT-B subscales, respectively. Reliability was assessed in terms of test-retest reliability using Cohen's kappa value and intra-class correlation coefficient (ICC).
  
  
  RESULTS
  The EQ-5D-3L index and EQ-VAS score were higher in the educated, current radiotherapy and unmarried groups. The correlation of EQ-5D-3L index and subscales for the FACT-B was highest in physical well-being (r = 0.553) and lowest in social well-being (r = 0.199). For reliability, the Kappa values' range was from 0.32 to 0.70, and ICCs of the EQ-5D-3L index and EQ-VAS scores were 0.70 and 0.48, respectively.
  
  
  CONCLUSIONS
  This study indicated that the EQ-5D-3L could be a valid health related quality of life instrument for postoperative breast cancer patients.
authors.affiliation: Department of Nursing, Dankook University, Cheonan, South Korea. kshgive@gmail.com.
authors.forename: Seon-Ha
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Preventive Medicine, University of Ulsan College of Medicine, 88, Olympicro 43-gil, Songpa-gu, 138-736, Seoul, South Korea. jominwoo@amc.seoul.kr.
authors.forename: Min-Woo
authors.initials: MW
authors.lastname: Jo
authors.affiliation: Department of Breast and Endocrine Surgery, Asan Medical Center, Seoul, South Korea. jjjongwr@hanmail.net.|Department of Surgery, University of Ulsan College of Medicine, Seoul, South Korea. jjjongwr@hanmail.net.
authors.forename: Jong-Won
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Preventive Medicine, University of Ulsan College of Medicine, 88, Olympicro 43-gil, Songpa-gu, 138-736, Seoul, South Korea. trueprsc@hanmail.net.
authors.forename: Hyeon-Jeong
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Nursing, Dankook University, Cheonan, South Korea. jongkimk@dankook.ac.kr.
authors.forename: Jong Kyung
authors.initials: JK
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People / Q000523:psychology*; D001943:Breast Neoplasms / Q000523:psychology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D056910:Republic of Korea; D011795:Surveys and Questionnaires