Determining the minimal important difference of the Oral Health Impact Profile for Chronic Periodontitis

Aim Building on previous psychometric work, we aimed to further assess the minimally important difference (MID) of the Oral Health Impact Profile for Chronic Periodontitis (OHIP‐CP). Methods In total, 240 consecutive patients with chronic periodontitis were recruited in the study. The OHIP‐CP was completed at baseline and after six weeks. Methodology testing included the confirmatory factor analysis (CFA) and MID. Confirmatory factor analysis (CFA) was performed to assess the fit of the previously proposed three‐factor model. The MID of this questionnaire was determined by applying anchor‐based and distribution‐based approaches. Results The CFA supported a three‐factor model for the OHIP‐CP with acceptable fit to the data. The fit indices were χ2/df = 2.231, GFI = 0.935, TLI = 0.969 and CFI = 0.976, RMSEA = 0.076. The OHIP‐CP scores showed significant improvements after treatment (p