Objective: To classify the evaluation methods for amount of tongue coating (TC) and investigate their reliability, accuracy, and frequency of use.
Methods: Articles published from 1985 to 2015 were searched for evaluation methods for the amount of TC in PubMed and the Cochrane Library. Only clinical researches were included except protocol articles. The methods were classified according to their characteristics.
Results: Finally, 113 articles were selected. The evaluation method for the amount of TC from the articles was classified into 4 types: intuitive, specificative, computerized, and weighing TC. The reliability in the intuitive and specificative methods (κ =0.33-0.92) showed varying levels among the studies. In general, the amount of TC calculated by the specificative method (Spearman's r=0.68-0.80) was more strongly related to the directly measured value than to the value estimated by the computerized method (Pearson's r=0.442). The number of articles published on this topic has increased consistently, and the specificative method was the most frequently used. Despite the higher reliability of the computerized method, it has not been widely used.
Conclusions: The high prevalence of the specificative method would continue in clinical practice because of its convenience and accuracy. However, to establish higher reliability, the limitation of the subjectivity of the assessors should be overcome through calibration training. In the computerized method, novel algorithms are needed to obtain a higher accuracy so that it can help the practitioners confidently estimate the amount of TC.
Keywords: accuracy; evaluation methods; frequency; reliability; tongue coating.