Avoidance of dental visits: the predictive validity of three dental anxiety scales.

The purpose of this study was to determine the sensitivity, specificity, positive and negative predictive values for Corah's Dental Anxiety Scale (DAS) and two modified versions of it (MDAS; MDAS/4). A questionnaire was mailed to a simple random sample of 1,190 25-year-old residents in the west of Norway in 1997. Half the sample received DAS, the other half MDAS. The response rate after one reminder was 62%. The respondents completed the scales, gave demographic particulars and answered one question about dental visiting habits during the last 5 years plus an open-ended question about reasons for non-attendance. Using the answers to the latter question as validating criterion, it was found that, for all scales, sensitivity decreased while specificity improved when changing from a liberal to a stringent cut-off point. The scales gave low positive predictive values (< or = 0.26), but high negative predictive values (> or = 0.98). Since DAS and MDAS/4 gave almost identical findings, the two samples were combined. At a cut-off point > or = 13 sensitivity was 0.83, specificity 0.84, positive predictive value 0.18 and negative predictive value 0.99. The corresponding estimates when the cut-off point was > or = 15 were 0.67, 0.90, 0.22 and 0.98. It is concluded that, in this test, DAS and the two versions of MDAS gave acceptable, or near acceptable sensitivity, specificity and negative predictive values, but far too low positive predictive values to be useful for prediction at the individual level.