Bias in retrospective assessment of perceived dental treatment effects when using the Oral Health Impact Profile

PURPOSE: Aim of this exploratory study was to investigate whether a retrospective assessment of oral health-related quality of life (OHRQoL) using the Oral Health Impact Profile (OHIP) is susceptible to bias such as implicit theory of change and cognitive dissonance.

METHODS: In this prospective clinical study, a sample of 126 adult patients (age 17-83 years, 49% women) requiring prosthodontic treatment was consecutively recruited. The OHRQoL was assessed using the 49-item OHIP at baseline and at follow-up. Additionally, patients were asked at follow-up to retrospectively rate their oral health status at baseline (retrospective pretest or then-test) and the change in oral health status using a global transition question. Furthermore, patients' ratings of overall oral health and general health were used as validity criteria for the OHRQoL assessments. Response shift was calculated as the difference between the initial and retrospective baseline assessments.

RESULTS: Baseline and retrospective pretest did not differ substantially in terms of internal consistency and convergent validity. Response shift was more pronounced when patients perceived a large change in OHRQoL during treatment. Retrospective pretests were more highly correlated with the baseline than with the follow-up assessment.

CONCLUSION: Findings suggest that retrospective assessments of OHRQoL using the OHIP-49 are susceptible to bias. Cognitive dissonance is more likely to appear as a source of bias than implicit theory of change.