Reliability and Validity of Oral Frailty Index-8: Findings Among Community-Dwelling Adults in Singapore

Oral Frailty Index-8 (OFI-8) is the earliest developed patient-reported measure for screening individuals at risk of oral frailty. However, there is limited information on its psychometric properties.

To evaluate the reliability and validity of OFI-8 in measuring oral frailty risk of community-dwelling adults in Singapore.

The OFI-8 was administered to 227 community-dwelling adults (aged 50 years and above), who then underwent oral health examination for number of functional teeth (FT), Eichner index (EI), oral health assessment tool (OHAT) score and oral frailty five-item checklist (OF-5) score. OFI-8 was assessed for its reliability (internal consistency, test-retest reliability and measurement error) and construct validity (structural, convergent and discriminative validities) based on Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) guidelines for testing patient-reported outcome measures.

The internal consistency (Cronbach's alpha = 0.61) and test-retest reliability (intra-class correlation coefficient = 0.62) were moderate, and standard error of measurement was 1.26. Confirmatory factor analysis revealed poor model fitting (comparative fit index = 0.77). The total OFI-8 score had moderate correlation with FT (r = -0.47, p < 0.001), EI (τ = 0.36, p < 0.001), weak correlation with OHAT score (r = 0.25, p < 0.001) and a strong correlation with OF-5 scores (r = 0.72, p < 0.001). The cut-off score (≥ 4) for oral frailty risk did not effectively distinguish between individuals with < 20 and ≥ 20 FT (Pearson chi-square test; p = 0.993).

OFI-8 demonstrated moderate reliability, limited structural validity, moderate convergent validity and moderate discriminative validity in measuring oral frailty risk of community-dwelling adults in Singapore.