Optimizing the design of visual analogue scales for assessing quality of life: a semi-qualitative study among Chinese-speaking Singaporeans

Objective Current recommendations for visual analogue scale (VAS) design are largely derived from studies on pain assessment. We evaluated respondent preferences for VAS design for health-related quality of life (HRQoL) assessment. Methods In-depth interviews were conducted among Chinese-speaking rheumatology outpatients and caregivers (age >= 21 years) to determine preferences for the following: (1) VAS orientation (horizontal/vertical); (2) length of instructions (long/intermediate/short); (3) scale range (0-10/0-100 points); (4) indicator for computerized touchscreen VAS (bar/column). Responses in subjects expressing a preference were compared using tests of proportions. Results Among 101 subjects, more subjects preferred a horizontal over a vertical format (48 vs. 37, P = 0.23; 16 no preference), and intermediate length over long/short instructions (44 vs. 14 vs. 31, P = 0.004; 12 no preference). A scale range of 0-10 was preferred over 0-100 (62 vs. 21, P < 0.001; 18 no preference). A bar indicator was preferred over a column for computerized touchscreen VAS (54 vs. 44, P = 0.31; 3 no preference). Only presence of chronic medical conditions influenced subject preference [odds ratio (95% confidence interval): 3.9 (1.6-9.6), P = 0.002]. Conclusion Chinese-speaking subjects preferred a 0-10-point VAS with intermediate length instructions for HRQoL assessment. Thus, a 0-10-point VAS with intermediate length instructions may be more useful for HRQoL assessment among Chinese subjects.