Assessment of the measurement properties of quality of life questionnaires in Brazilian women with breast cancer

BACKGROUND:

There are several questionnaires available to assess quality of life in breastcancer, however the choice of the best questionnaire often does not take intoaccount the adequacy of these questionnaires'' measurement properties.

OBJECTIVE:

To test the measurement properties of two generic quality of life questionnairesand one quality of life questionnaire specific for women with breast cancer.

METHOD:

We assessed 106 women after surgery for breast cancer. The assessment includedapplication of the SF-36, WHOQOL-bref, and FACT-B+4 questionnaires as well as theGlobal Perceived Effect and Pain Numerical Rating scales. The participants wereinterviewed on three occasions to investigate internal consistency, floor andceiling effects, construct validity, reproducibility, and responsiveness.

RESULTS:

Most of the instruments'' domains showed adequate internal consistency (Cronbach''salpha varying from 0.66 to 0.91). Reliability varied from poor to substantial(ICC_2,1 between 0.39 and 0.87) and agreement varied from negative tovery good. The SF-36 presented doubtful agreement and showed floor and ceilingeffects in three domains. The domains of the generic questionnaires presentedmoderate to good correlation with the FACT-B+4 (Pearson varying from 0.31 to0.69). The internal responsiveness varied from small to large (ES varying from-0.26 to 0.98) and external responsiveness was found in only some of theinstruments'' domains.

CONCLUSIONS:

Most of the measurement properties tested for the WHOQOL-bref and FACT-B+4 wereadequate as was their ability to assess quality of life in women with breastcancer. The SF-36 showed inadequacy in agreement and floor and ceiling effects andshould not be used in women with breast cancer.