Diagnostic performance of ICDAS for root caries: comparison with histological reference standards

Evidence regarding the performance of visual test for root caries severity assessment is still limited. This in vitro diagnostic performance study evaluated visual test with ICDAS (International Caries Detection and Assessment System) root criteria against three histological reference standards -stereomicroscopy (SM), polarised-light microscopy (PLM), and micro-computed tomography (micro-CT).

A total of 125 extracted permanent teeth were classified with the visual test using ICDAS root criteria. Histological evaluation was performed using SM and PLM. In addition, in a subsample of 22 teeth was assessed further using micro-CT. Discriminative power, global and categorised performance (confidence interval with a 95% confidence level) and agreement (Cohen's Kappa and percentage), and indicators of validity and diagnostic utility (sensitivity, specificity, positive and negative predictive values - PPV and NPV, likelihood ratios - LR+ and LR-) were stablished.

Compared with histological reference standards, the visual-tactile test showed moderate to high diagnostic performance for root caries for sensitivity (≥ 0.73), specificity (≥ 0.90), and predictive values (PPV ≥ 0.71, NPV ≥ 0.91). Overall likelihood ratios supported moderate confirmatory value (LR+ = 7.43-9.39) and rule-out ability (LR- = 0.26-0.30) after visual-tactile classification. Agreement between the visual test and the histological references was substantial (weighted kappa ≥ 0.88), with moderate discriminative power (0.63-0.68). Complete observed agreement was found for the sound category. Performance was high for initial caries (≥90% for sensitivity, specificity, and predictive values; LR+ ≥10; discriminative power ≥0.82), whereas extensive lesions showed good rule-out ability but lower confirmatory value.

The visual-tactile test showed substantial agreement against histological reference standards, moderate to high diagnostic performance, and moderate discriminative power. The test showed complete observed agreement for sound surfaces and high performance for identifying initial caries, whereas extensive lesions showed good rule-out ability but lower confirmatory value. These findings support the visual-tactile ICDAS root caries criteria as useful for the detection and assessment of root caries lesions.