Development of a Greek Oral health literacy measurement instrument: GROHL.

Oral health literacy is an important construct for both clinical and public health outcomes research. The need to quantify and test OHL has led to the development of measurement instruments and has generated a substantial body of recent literature. A commonly used OHL instrument is REALD-30, a word recognition scale that has been adapted for use in several languages. The objective of this study was the development and testing of the Greek language oral health literacy measurement instrument (GROHL). Data from 282 adult patients of two private dental clinics in Athens, Greece were collected via in-person interviews. Forty-four words were initially considered and tested for inclusion. Item response theory analysis (IRT) and 2-parameter logistic models assessing difficulty and discriminatory ability were used to identify an optimal scale composition. Internal consistency was examined using Cronbach's alpha and test-retest reliability was measured using intraclass correlation coefficient (ICC) in a subset of 20 participants over a two-week period. Convergent validity was tested against functional health literacy screening (HLS) items, dental knowledge (DK), oral health behaviors (OHBs), oral health-related quality of life (OHRQoL; OHIP-14 index), as well as self-reported oral and general health status. From an initial item pool of 44 items that were carried forward to IRT, 12 were excluded due to no or little variance, 10 were excluded due to low item-test correlation, and 2 due to insignificant contribution to the scale, i.e., difficulty parameter estimate with p > 0.05. The twenty remaining items composed the final index which showed favorable internal consistency (alpha = 0.80) and test-retest reliability (ICC = 0.95). The summary score distribution did not depart from normality (p = 0.32; mean = 11.5; median = 12; range = 1-20). GROHL scores were positively correlated with favorable oral hygiene behaviors and dental attendance, as well as HLS, DK and education level. The GROHL demonstrated good psychometric properties and can be used for outcomes research in clinical and public health settings.