Background: Childsmile School adopts a directed-population approach to target fluoride varnish applications to 20% of the primary one (P1) population in priority schools selected on the basis of the proportion of enrolled children considered to be at increased-risk of developing dental caries. The study sought to compare the effectiveness of four different methods for identifying individuals most in need when a directed-population approach is taken.
Methods: The 2008 Basic National Dental Inspection Programme (BNDIP) cross-sectional P1 Scottish epidemiological survey dataset was used to model four methods and test three definitions of increased-risk. Effectiveness was determined by the positive predictive value (PPV) and explored in relation to 1-sensitivity and 1-specificity.
Results: Complete data was available on 43,470 children (87% of the survey). At the Scotland level, at least half (50%) of the children targeted were at increased-risk irrespective of the method used to target or the definition of increased-risk. There was no one method across all definitions of increased-risk that maximised PPV. Instead, PPV was highest when the targeting method complimented the definition of increased-risk. There was a higher percentage of children at increased-risk who were not targeted (1-sensitivity) when caries experience (rather than deprivation) was used to define increased-risk, irrespective of the method used for targeting. Over all three definitions of increased-risk, there was no one method that minimised (1-sensitivity) although this was lowest when the method and definition of increased-risk were complimentary. The false positive rate (1-specificity) for all methods and all definitions of increased-risk was consistently low (<20%), again being lowest when the method and definition of increased-risk were complimentary.
Conclusion: Developing a method to reach all (or even the vast majority) of individuals at increased-risk defined by either caries experience or deprivation is difficult using a directed-population approach at a group level. There is a need for a wider debate between politicians and public health experts to decide how best to reach those most at need of intervention to improve health and reduce inequalities.