Comparison of Microbiologic Methods Used in Caries Risk Assessment(CRA)

Objectives: Objective: Caries Risk Assessments(CRA) are improved with robust microbiologic findings. Our objective was to determine the potential contribution of different bacterial assessments on CRA to better reflect the ecological nature of disease development.
Methods: Methods: The cohort was comprised of 29 patients assigned to low caries risk (n=20) or high caries risk (n=9) by the standardized UCSF CRA form. Additionally low caries risk subjects had no decay for the last three years, and high caries risk subjects had active caries. Measurements included plaque adenosine triphosphate(ATP) measurements (CariScreen) and salivary bacteria loads with the CRT^® culture kit (ivoclar vivadent) to determine levels of mutans streptococci and lactobacilli. Additionally, the ratio of S.mutans vs. spxB a highly conserved gene among oral commensal streptococci encoding pyruvate oxidase was measured using loop-mediated isothermal amplification(LAMP). The ratio was assessed with specific LAMP-primers for S.mutans and specific LAMP primers for spxB. Sample analysis was blinded as to patients risk.
Results: Results: Sensitivity, Specificity and Likelihood Ratios(LR) were calculated. Likelihood ratios exceeded 2 only for high CRT^® readings (mutans streptococci=5 or 6, plus lactobacilli=5 or 6, LR:2.2) and S.mutans/spxB ratios greater than 1 (LR: 2.75). Likelihood Ratios below .5 were calculated for CRT^® readings (mutans streptococci =3,4, or 5 and lactobacilli =3 or 4, (LR:0.2) and S.mutans/spxB ratio less than 1 (LR:0.22). ATP is a dichotomous test with Sensitivity=77%, Specificity=50% and LR=1.54.
Conclusions: Conclusion: Important tests can change decision-making. Valid tests alter “pre-test” probability to better inform “post-test“ probability of disease. LRs 2-5 and 0.2-0.5 generate small but sometimes important changes in disease probability (Guyatt, A.M.A.- Users Guides to the Medical Liturature,2008). Improved multilevel microbiologic assessment including biofilm physiologic dynamics may enhance clinician’s ability to interpret CRA.