Reliability, validity and cutoff score of the Intra-Oral Injection Fear scale

Background A proper assessment tool is needed to gain more knowledge about fear of intraoral injections in children. Aim The aims of this study were to evaluate the reliability and validity of the novel Intra-Oral Injection Fear scale (IOIF-s) and to establish a cutoff score for a high level of such fear. Methods Data were obtained from two samples of 10- to 16-year-olds in Hordaland, Norway. Sample I, 1460 pupils attending elementary and high schools, provided questionnaire-based data. The survey instruments used were IOIF-s, Children's Fear Survey Schedule-Dental Subscale (CFSS-DS), Mutilation Questionnaire for Children (MQ-c) and Injection phobia Scale for Children (IS-c). Sample II was 67 patients, diagnosed with intraoral injection phobia at the Center for Odontophobia, Oral Health Center of Expertise in Western Norway-Hordaland, who provided IOIF-s data. Results Cronbach's alpha was 0.95. The IOIF-s discriminated between subjects with and without intraoral injection phobia and was associated with the other survey instruments of similar construct. Principal component analysis revealed a two-component solution, characterized as ‘Contact Fear’ and ‘Distal Fear’. Receiver-operating characteristic (ROC) curve indicated that a cutoff score of 38 was appropriate. Conclusion The IOIF-s showed satisfying psychometric properties in terms of reliability and validity.