Background Past caries experience is widely recognised as the strongest indicator of future caries. However, relying on ‘past caries’ is suboptimal, as it identifies risk only after the disease onset.Objective This cohort study evaluated the accuracy of Streptococcus mutans (S. mutans) level, assessed by immunoassay and culture-based test, in predicting caries, using ‘past caries’ as a benchmark predictor.Design Based on a sample size calculation, 190 children aged 3–4 years were recruited. The level of S. mutans in their stimulated saliva was measured using a chairside, monoclonal antibody-based immunoassay and a culture-based test. Caries status (dmft) was recorded at baseline (past caries) and reassessed after 12 months to measure caries increment (Δdmft). A multifactorial analysis was conducted to evaluate the associations between caries increment and potential caries indicators, adjusted for sociodemographic and behavioural variables. The diagnostic accuracy of the three indicators (S. mutans immunoassay, S. mutans culture-based and ‘past caries’) in predicting future caries (Δdmft > 0) was evaluated and compared based on all possible diagnostic cut-offs.Results Children identified by the immunoassay as having a high level of S. mutans (≥5 × 10⁵ CFU/mL) had a significantly greater mean caries increment (Δdmft) compared to those with lower levels (1.66 ± 1.40 vs. 0.27 ± 0.90; p < 0.001). For the culture-based test, the mean caries increments across Scores 0–3 were 0.31 ± 1.02, 0.42 ± 0.84, 1.00 ± 1.21 and 1.56 ± 1.79, respectively, with significant differences only between some groups (Score 0 vs. 2/3, Score 1 vs. 3; p < 0.05). The sensitivity/specificity for caries prediction was 70.4%/92.1% for the immunoassay, 70.4%/73.7% for the culture-based test and 70.4%/83.3% for ‘past caries’.Conclusions S. mutans immunoassay demonstrated comparable sensitivity and higher specificity than S. mutans culture-based test and ‘past caries’ in predicting future caries. With a combined sensitivity and specificity exceeding 160%, the S. mutans immunoassay offers a valuable chairside method for caries risk assessment and optimised treatment planning.
Natarajan et al. (Thu,) studied this question.