Diagnostic accuracy of the Oral Aesthetic Subjective Impact Score (OASIS) questionnaire for orthodontic treatment need in Nepal: a hospital-based study

The Oral Aesthetic Subjective Impact Score (OASIS) is a questionnaire used to assess self-perception of dental aesthetics. This study aimed to assess the diagnostic accuracy of this questionnaire in determining orthodontic treatment need in Nepali patients and to establish an appropriate cut-off score. The original OASIS questionnaire was translated and adapted into the Nepali language. A total of 145 participants aged 14–19 years completed the Nepali version of OASIS (OASIS-N) questionnaire and rated their dental aesthetics on a Visual Analogue Scale. Orthodontic treatment need was then evaluated using the Index of Orthodontic Treatment Need-Dental Health Component (IOTN-DHC) and Aesthetic Component (IOTN-AC). Receiver Operating Characteristic (ROC) analysis was done to assess diagnostic accuracy of the OASIS-N against IOTN-DHC, and to identify the optimal cut-off score. Sensitivity, specificity, and predictive values were calculated for different cut-off scores. OASIS-N demonstrated high internal consistency (Cronbach’s α = 0.88) and good test–retest reliability (ICC = 0.77). It showed good diagnostic accuracy for detecting orthodontic treatment need, with an area under the ROC curve (AUC) of 0.945 (95% CI: 0.911–0.979). A cut-off score of 14.5 provided the best balance of sensitivity (90.4%) and specificity (75.6%) with substantial agreement with IOTN-DHC (κ = 0.660, p < 0.001). OASIS-N demonstrated good diagnostic accuracy for identifying orthodontic treatment need in Nepal. A cut-off score of 14.5 provided the best balance of sensitivity and specificity. Further multi-centre validation in community-based populations is recommended.