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TRANSLATION AND APPLICATION OF THE NUMERACY UNDERSTANDING IN MEDICINE INSTRUMENT IN JAPAN

Monday, October 21, 2013
Key Ballroom Foyer (Hilton Baltimore)
Poster Board # P2-39
Decision Psychology and Shared Decision Making (DEC)

Masako Okamoto, Ph.D.1, Yasuchi Kyutoku, Ph.D.2, Cynthia M. Walker, Ph.D.3, Tamara Miller, PT, MS3, Yurie Sugimoto4, Lester Clowney5, Ippeita Dan, Ph.D.2 and Marilyn Schapira, MD, MPH6, (1)Obihiro University of Agriculture and Veterinary Medicine, Obihiro Hokkaido, Japan, (2)Chuo University, Tokyo, Japan, (3)University of Wisconsin, Milwaukee, WI, (4)Kyushu Institute of Technology, Tokyo, Japan, (5)Jichi Medical University, Tochigi, Japan, (6)University of Pennsylvania, Philadelphia, PA
Purpose: Although understanding numerical information is a crucial factor when people make medical decisions, health numeracy has been understudied in Japan due to the absence of adequate assessment tools. In the United States, one such tool is Numeracy Understanding in Medicine Instrument (NUMi; Schapira et al., 2012), which was developed based on empirically derived health numeracy framework. In the current study, we examined the validity of the NUMi for the Japanese public, and compared the Japanese (NUMi-J) and original versions.

Method: NUMi-J was prepared using a forward and backward translation, with context and wordings modified based on feedback from three experts and pilot respondents (N=1054). In the primary study, responses from a quota sample (N=2000) approximating the composition of the Japanese population were collected. As in the original study, both classical test theory (CTT) and item response theory (IRT) were used to examine the psychometrical nature of the NUMi-J. Validity was assessed by examining the association of NUMi-J scores with other measures of numeracy, literacy, psychographics and levels of understanding of medical information.

Result: The performance of Japanese sample demonstrated higher numeracy than in the original study (mean scores of 14.5 vs. 13.2, respectively). Consequently, the IRT parameter for difficulty was lower with the 20 items ranging respectively from -2.70 to 0.96 in the current, and –1.70 to 1.45 in the original study. Except for difficulty parameter, the results from NUMi-J were comparable with the original ones, with sufficient reliability (Cronbach α=0.83) and discriminability (range of IRT parameter 0.33 to 2.48). As expected, performance on NUMi-J demonstrated a higher correlated with numeracy scores (11-item objective scale, r=0.52; Berlin Numeracy test, r=0.47) than print literacy scores (Health knowledge test, r=0.35; Science literacy test, r=0.40), or psychographic scores (Rational-Experiential Index-ability, r=0.19; Self-efficacy, r=0.05). Finally, logistic regression analysis indicated that the predictive ability of NUMi-J on the understanding of quantitative medical information to be the best among all the other parameters (numeracy, literacy and psychographic; All the independent variables were standardized; odds ratio of NUMi-J, 2.3).

Conclusion: In its translated form, NUMi worked well in this culturally different population, and will be a useful tool for assessing patients’ health numeracy in Japan, especially for those with relatively lower numeracy levels.

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