Modified Dental Anxiety Scale: Evidence for the 19 point cut-off

The Modified Dental Anxiety Scale (MDAS) is a 5 question self-report scale for assessing an individual's dental anxiety (Humphris et al. 1995). It can be used in epidemiological surveys as well as clinical studies where a brief score estimating dental anxiety is required. It has the advantage of being quickly administered, featuring good psychometric properties and consistent answering scheme across items. The scale when summed together exhibits a range of a minimum of 5 to a maximum of 25. The original report provided a rationale with some evidence for setting the cut-off as 19 for respondents with ‘high dental anxiety'. This group may require additional assistance in the surgery to receive dental treatment.

Objective: To obtain further evidence for setting the cut-off at 19.

Methods: A web-based survey was advertised on the University of St Andrews dedicated intranet for student access (undergraduate and postgraduate). The form was designed for completion ‘on line'. Measures included the MDAS and four questions based upon the DSM-Rv4 to assess dental phobia. Instructions were supplied and a debriefing sheet was posted on completion of questions. The survey was passed by the University Ethics Committee. All replies were anonymous. The survey was posted from November 2008 to March 2009.

Results: 1064 replies were collected. 1024 replies had complete information (67% female, 93% aged 16 to 25 years).The scale showed excellent reliability (Cronbach's alpha = 0.93) and unidimensionality (chi-sq=5.47, df2, p=.065, CFI=.999; RMSEA=.041 [.000 to .081]. 11.1% of students were categorised as highly anxious (at or above cut-off of 19). Seven respondents were designated as ‘dental phobics'. ROC curve analysis confirmed that the cut-off of 19 was the most suitable, sensitivity=86%, specificity=89%; Area Under the Curve=0.92, z=5.89, p=.0001.

Conclusion: The MDAS scale cut-off of 19 is confirmed.