The impact of literacy on health-related quality of life measurement and outcomes in cancer outpatients

Abstract

Limited evidence exists regarding the relationship between literacy and health-related quality of life (HRQL). Research is needed to develop measurement techniques for low literacy populations and to evaluate potential literacy-related measurement bias. A Talking Touchscreen (TT) was developed for an HRQL study. Low (n = 214) and high literacy (n = 201) adult cancer outpatients participated, 70% of whom were from racial/ethnic minorities. Patients completed three questionnaires by TT: FACT-G (cancer-specific), SF-36 (generic health status), and a standard gamble utility questionnaire. Measurement bias was evaluated using item response theory (IRT). Effects of literacy on HRQL were evaluated using regression models. Most (97%) patients rated the TT easy to use. In IRT analysis, 6/27 FACT-G and 12/31 SF-36 items demonstrated literacy bias; this was relatively balanced (10 items 'biased against' low literacy; 8 'biased against' high literacy). Mean literacy group differences were statistically and clinically non-significant for 9/14 HRQL outcomes. Adjustment for bias and/or covariates eliminated most remaining differences. The TT is valid and useful for HRQL assessment in low literacy populations. There appears to be no systematic literacy bias in reporting HRQL, and low literacy is not an independent risk factor for poorer HRQL.