Materials and Methods: Two exploratory surveys were conducted in populations supposed to have LUTS. In the first survey, after explanation, 49 participants were tested with the original IPSS Thai version and a new preliminary version A. They rated the level of ease-difficulty in understanding of both versions. In the second survey, with 135 respondents, three versions were tested; the original, the preliminary version A and B, without explanation given. There were observers detecting respondents’ problems in completing the questionnaires. The problems were evaluated using Student’s t-test, ANOVA, univariate, and multivariate analyses.

Results: In the first survey, the preliminary version A was significantly easier to understand from the ease-difficulty score, while the second survey showed no difference among all three versions. Four problems were detected, which were rating number confusion, proportional number misunderstanding, the second question misunderstanding, and preliminary versions doubt. With higher ages, more problems existed, but with higher education, fewer misunderstandings appeared. Lower educated respondents, junior high school, and primary school level or below were about 3 and 16 times more likely to experience problems, respectively. The problems were almost 6-fold more likely to occur in respondents older than 70 years. With low education and old age occurring together, problems were much more likely to appear (OR 91.00, 95% CI 10.59 to 781.63).

Conclusion: There were some misunderstandings and misinterpretation problems in the IPSS Thai version, which were more likely to occur in low educated and/or elderly responders. The validity and reliability of the modified version of Thai IPSS will be further studied.

Keywords: International Prostate Symptom Score, IPSS, Thai version, Misunderstanding/misinterpretation, Problem