Developing short-form measures of oral health-related quality of life

Objectives: Using the item-impact method, we developed an alternative short-form Oral Health Impact Profile (OHIP) that has good psychometric properties and minimal floor effects. Methods: OHIP data were collected from a sample of older Canadians at two points in time. Data from the first administration were used to develop a 14-item short-form measure; data from the second compare the latter's psychometric properties with those of the original short form developed by Slade (1997), who used a controlled regression procedure. Results: The short form based on the item-impact method had only two items in common with the short form derived from the regression approach and contained more high-prevalence items. The regression short form was subject to marked floor effects, while the impact short form had floor effects comparable to those of the full 49-item OHIP. The former discriminated between dentate and edentulous subjects, while the latter did not. Both discriminated between dentate subjects who did and did not wear dentures, those with and without dry mouth, and those with and without chewing problems. Both were also significantly associated with self-ratings of oral health satisfaction with oral health, and self-perceived need for dental treatment. The strength of the associations was somewhat stronger with the regression short form, indicating that it performed better as a discriminatory instrument However, because of its floor effects, it was markedly less sensitive to change than the impact short form. There was an indication that item-impact methods of shortening oral health-related quality of life measures produced more stable results across samples than the statistical approach. Conclusions: Because the content validity of short-form measures is always compromised, different short forms are required for different purposes and different patient populations. The regression short form developed by Slade (1997) is likely to be better when the aim is to discriminate, while the impact short form developed here may be preferable when the aim is to describe the oral health-related quality of life of populations or to detect change.