Confirming the Minimal Important Difference of the Oral Health Impact Profile

Abstract

Aim: This study aimed to confirm the Minimal Important Difference (MID) of Oral Health Impact Profile (OHIP) in dental patients. Materials and Methods: In this observational study a consecutive sample of 1896 adult patients completed the OHIP questionnaires twice, one questionnaire before the treatment was performed and a second at follow-up about 6 months after the initial visit. At both visits, scores for the 49-item, the 14-item, and the 5-item version were calculated. In addition, at follow-up, the patients (N=199) rated the overall change in their perceived oral health using a 7-point global scale (oral health worsened very much to improved very much). For the N=36 patients reporting a “minimal improvement”, the median of OHIP change scores (OHIP baseline – OHIP follow up) and a confidence interval was computed. This value was considered the Minimal Important Difference (MID) for OHIP. It was computed for OHIP-49, OHIP-14, and OHIP-5. MIDs were also computed for females versus males, less than 60 years old patients versus 60 and older patients, and patients with lower versus higher OHRQoL impairment at baseline (split at the OHIP49 score median at baseline). Results: The MID for the 49-item OHIP was 4.5 points (95% confidence interval: -3.8 to 11.3). The same values were -1 (95% CI: -1.0 to 2.0) and 0 (95% CI: 0.0 to 2.0) for OHIP-14 and OHIP-5. We did not find a gender or age influence on OHIP-49, 14, and 5’ MID, but demonstrated an influence of the magnitude of baseline OHRQoL impairment on OHIP-5. Conclusion: The results in our study corroborate the findings in the previous research about the Minimal Important Difference of OHIP instruments. OHIP’s MID seems to be similar across settings. However, we also found an influence of the magnitude of the OHRQoL impairment, indicating that MID is not one value that can be applied across settings. Our OHIP’s MID values can be used as benchmarks to judge the clinical relevance of the changes in perceived oral health when measured with OHIP.