Development and validation of the General Health Numeracy Test (GHNT)

Abstract

ObjectiveBecause existing numeracy measures may not optimally assess ‘health numeracy’, we developed and validated the General Health Numeracy Test (GHNT). MethodsAn iterative pilot testing process produced 21 GHNT items that were administered to 205 patients along with validated measures of health literacy, objective numeracy, subjective numeracy, and medication understanding and medication adherence. We assessed the GHNT's internal consistency reliability, construct validity, and explored its predictive validity. ResultsOn average, participants were 55.0±13.8 years old, 64.9% female, 29.8% non-White, and 51.7% had incomes ≤$39K with 14.4±2.9 years of education. Psychometric testing produced a 6-item version (GHNT-6). The GHNT-21 and GHNT-6 had acceptable-good internal consistency reliability (KR-20=0.87 vs. 0.77, respectively). Both versions were positively associated with income, education, health literacy, objective numeracy, and subjective numeracy (all p<.001). Furthermore, both versions were associated with participants’ understanding of their medications and medication adherence in unadjusted analyses, but only the GHNT-21 was associated with medication understanding in adjusted analyses. ConclusionsThe GHNT-21 and GHNT-6 are reliable and valid tools for assessing health numeracy. Practice implicationsBrief, reliable, and valid assessments of health numeracy can assess a patient's numeracy status, and may ultimately help providers and educators tailor education to patients.