Reliability and Validity of the Oral Health Impact Profile (OHIP-14)

Objectives: To assess the reliability and validity of the Spanish version of the Oral Health Impact Profile (OHIP-14) in teachers of public schools in the city of Bucaramanga (Colombia).
Methods: An evaluation of diagnostic technology was performed with 346 adults (mean age 47.2 ± 10.8 years) who filled out the Spanish version of the OHIP-14. Both institutions and teachers were randomly selected, first by cluster sampling in 30 public schools and second, by simple random sampling. The analyses were conducted on the entire sample as well as for age groups (20-49 and 50-67 years), gender and socioeconomic conditions (low and high). The internal consistency was estimated via Cronbach’s alpha coefficient as a measure of reliability of the OHIP-14 scores, values of 0.7 or higher were considered acceptable. The rating scale structure, item quality, invariance structure and unidimensionality of the questionnaire were analyzed. Invariance structure was tested via Differential Item Functioning (DIF) by gender, age groups and socioeconomic condition. Stata version 12.0 and Winsteps^® software were used. Informed consents were obtained.
Results: It was found that 216 (62.4%) were women and 74 (21.4%) teachers presented the minimum score (zero) indicating an excellent oral health related quality of life. A Cronbach alpha of 0.93 for all OHIP-14 scores was observed. Rasch item curves indicated disordered thresholds between the five response categories so two of them were re-scored and collapsed resulting in three response options. Eight items showed misfit and were dropped. The infit and outfit mean square ranged between 0.82 to 1.24 and 0.83 to 1.16, respectively. Uniform DIF was not observed. The measurements explained 54.3% of the variance. This value might suggest the unidimensionality of the questionnaire.
Conclusions: The Spanish version of the OHIP-14 showed excellent levels of reliability and satisfactory levels of validity having in mind that six items were dropped.