Appropriateness of using numeric rating scales to assess risk perceptions for individuals with limited health numeracy

Objective: Numeric rating scales (NRSs) could be inappropriate for assessing constructs such as risk perception if individuals with limited health numeracy (LHN) have difficulty expressing their perceptions on such scales. This paper compares the psychometric functioning of numerical risk perception ratings for an e-cigarette obtained from LHN individuals, comparing them to those from individuals with adequate health numeracy (AHN). Methods: In a randomized trial of a risk-related message (not evaluated here), participants (N = 12,557) used NRSs to rate their perception of (1) overall risk of harm (from 0 %−100 % harmful to health), and (2) likelihood (0–100 %) of suffering four tobacco-related diseases from using e-cigarettes; and used a 4-point adjectival scale (‘not at all harmful’ to ‘very harmful’) to rate the harm of using e-cigarettes. Based on the Newest Vital Sign (NVS), 29 % of participants were classified as LHN. Results: Numeric ratings of e-cigarette harm in LHN and AHN groups showed a nearly identical and equally strong relationship to verbal perceived risk ratings. Analyses of disease-specific ratings as a unidimensional scale demonstrated configural, metric, and scalar invariance between ratings from LHN and AHN individuals. Conclusion: LHN individuals are able to make meaningful ratings using numeric scales, comparable to those from AHN individuals.