Blind chance? An investigation into the perceived probabilities of phrases used in oral radiology for expressing chance.

The necessity for numerical probabilities in oral radiographic diagnosis is increasing, due to recent developments in computer-aided diagnosis, decision analysis, informed consent and medical litigation. These numerical probabilities are only partly available from current texts on oral radiology, where they are often expressed by ill-defined, semiquantitative phrases. Therefore, in this study 30 phrases expressing the probability of a relationship between a diagnosis and its symptoms were taken from a selected textbook on oral radiology. Seven oral radiologists from the USA and the Netherlands scored each of these probabilistic phrases on a 20-cm visual analogue scale. Low intraradiologist and high interradiologist variation was found. Because the high variation among authors of texts on oral radiology in interpreting probability information could have a negative influence on their ability to transfer unambiguous information to their readers, it is recommended that the use of semiquantitative phrases in oral radiology is restricted to five probability groups.