Instrument-order effects: using the Oral Health Impact Profile 49 and the Short Form 12.

Whereas it is well known that the ordering of items can influence research outcomes considerably, very little literature addresses instrument-order effects. Therefore, the aim of this study was to evaluate the effect of changing the administrative order of the Short-Form-12 (SF-12) and the Oral Health Impact Profile-49 (OHIP-49). It was hypothesized that if the SF-12 was administered first, the results would show poorer scores on the SF-12 subscales, as responses would not be restrained to only the oral impacts described by the OHIP-49. Using the Mann-Whitney U-test no significant instrument-order effects were found, except for the Psychological discomfort scale of the OHIP-49, where subjects scored higher when receiving the OHIP-49 first. However, the effect size was negligible (-0.08). These results suggest that no instrument-order effects occurred. Nonetheless, more research dealing with different instruments is needed. This study was performed within a dental setting and we recommend that instrument-order effects should be studied outside this domain.