Validation of the test Newest Vital Sign Test for measuring health care literacy in Primary Care

Background: Health literacy is a determinant, powerful predictor of health. The Newest Vital Sign test (NVS) evaluates health literacy assessing the capacity of participants to understand the nutrition information label of an ice cream. Aim: To validate The NVS test for its application in the sociocultural context on primary care patients in Chile. Material and Methods: In a descriptive cross-sectional study, 1,117 people aged 58 +/- 14 years (70% women) registered in the Cardiovascular Health Program of different Family Health Centers, answered the NVS test. They also answered the Test of Functional Health Literacy for Adults (TOFHLA) and the Health Literacy Survey, European Union (HLS-EU-32). An exploratory analysis was carried out. In addition, the Kuder-Richarson-20 reliability coefficient and Item-Test Point Biserial Correlations were calculated. The construct validity of the NVS was obtained using the Item Response Theory. The sensitivity and specificity of NVS were estimated using receiver operating characteristic curves using the TOFHLA score as gold standard. To establish the cut-off points, the Stratum-Specific Likelihood Ratio analysis was used. Results: The reliability of the test was adequate (KR-20 = 0.7478) and the values of the two logistic parameters model confirmed that the NVS items account for the health literacy construct. Conclusions: The NVS test turned out to be a valid and reliable instrument, and its application is recommended to measure the level of health literacy.