Average area under the curve: An alternative method for quantifying the dental caries experience in longitudinal studies.

Objectives: Field-traditional decayed, missing, filled surfaces (dmfs) increments require complete follow-up, only using initial and final visits. Repeated dmfs scores complicate sophisticated statistical models, limiting their utility. Elsewhere, area under the curve (AUC) uses all repeated measures to summarize data. This study applied AUC methodology to caries data, creating average AUCs for dmfs trajectories (dmfs ) and comparing increments and dmfs values.

Methods: Longitudinal data were obtained from high-caries risk (i.e. poor, rural, African American community in Perry County, Alabama) infants, 8 to 18 months at baseline. Baseline and five annual visual oral examinations provided dmfs scores. Differences in baseline and final dmfs scores constituted increments. The trapezoidal rule was applied to dmfs trajectories to calculate AUC values which were adjusted for varying follow-up times, producing dmfs values. Participants sharing incremental or dmfs values had their trajectories and second caries measurements compared. Within-participant increment and dmfs differences were evaluated (paired t test, α = 0.05). Comparative analyses required complete follow-up.

Results: The dmfs provided forty-eight additional person-years, increasing the potential sample size by 20% (N = 85). Sixty-six children, 5.7 to 6.3 year-olds at study's end, contributed 121 331 person-days to five-year increment and dmfs calculations. Trajectories and dmfs values varied for participants with equivalent increments; comparable trajectories and different increments resulted from participants with similar dmfs values. Within-participant disease amounts were similar.

Conclusions: When desired, dmfs can replace increments as a more data-inclusive summary of longitudinal caries burden, incorporating intermediate visits, incomplete follow-up and time.