Identifying Predictive Values and Correlations with Caries using Cutoff Points (various pH levels) in the Cariostat Caries Activity Test

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The sample size was 1206 Japanese children born in 2000 who were examined for dental caries at 18, 24, and 40 months; pH caries activity tests and short questionnaires were administered. The overall caries prevalence was 8.7% for 2-year-olds. The follow-up time was sufficient.

Key Exposure/Study Factor

The primary prognostic factor of interest is the pH cutoff points of the Cariostat caries activity test. The authors also had survey questions regarding brushing and dietary habits and correlated them to caries prevalence.

Main Outcome Measure

The primary disease that was to be predicted by the test was dental cavitations. The results of the pH test were unknown to those who performed the clinical examination.

Main Results

The various cutoff points of the Cariostat test were used to determine sensitivity, specificity, validity (adding the results of the sensitivity and specificity scores), positive predicative value, negative predictive values, as well as correlation of caries prevalence. It was found that those subjects with low caries activity scores (produced little acid) had a high sensitivity, but low specificity to caries prevalence; whereas those with high caries activity scores (produced more acid) had low sensitivity, but high specificity. (This is a little mind bending, and it seems backwards.) Overall, the validity of the test, considering all the cutoff point was low, with the highest number achieving only 1.28. Correlations of the various cutoff points with caries was statistically significant, but also low with correlations of 0.07 for 18-month-olds and 0.176 for 2-year-olds for prevalence and 0.147 and 0.223 for incidence for 24- and 40-month-olds, respectively.


The cutoff points of the Cariostat caries risk assessment add further information to the usefulness of this test. Although the results were significant, the validity of this test at various cutoff points is not high.

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