Quick screen of patients' numeracy and document literacy skills: the factor structure of the Newest Vital Sign

INTRODUCTION: The Newest Vital Sign (NVS) is a survey designed to measure general health literacy whereby an interviewer asks six questions related to information printed on a nutritional label from an ice cream container. It enables researchers to evaluate several health literacy dimensions in a short period of time, including document literacy, comprehension, quantitative literacy (numeracy), application, and evaluation. No study has empirically examined which items belong to which latent dimensions of health literacy in the NVS using factor analysis. Identifying the factor structure of the NVS would enable health care providers to choose appropriate intervention strategies to address patients' health literacy as well as improve their health outcomes accordingly. This study aimed to explore the factor structure of the NVS that is used to assess multiple dimensions of health literacy. METHODS: A cross-sectional study administering the NVS in a face-to-face manner was conducted at two family medicine clinics in the USA. One hundred and seventy four individuals who participated were at least 20 years old, diagnosed with type 2 diabetes, prescribed at least one oral diabetes medicine, and used English as their primary language. Exploratory factor analysis and confirmatory factor analysis were conducted to investigate the factor structure of the NVS. RESULTS: Numeracy and document literacy are two dimensions of health literacy that were identified and accounted for 63.05% of the variance in the NVS. Internal consistency (Cronbach's alpha) of the NVS were 0.78 and 0.91 for numeracy and document literacy, respectively. CONCLUSION: Numeracy and document literacy appropriately represent the factor structure of the NVS and may be used for assessing health literacy in greater detail for patients with type 2 diabetes.