Testing the internal and external validity of a simplified dental caries index on an adult population

This analysis of a caries index, proposed in 1966 to WHO as a simplified method of measurement, as tested on a 16- to 45-year-old population who were seeking dental care at the University of Minnesota School of Dentistry revealed several weaknesses associated with the index. An analysis of the external validity of this index, a comparison with subjects' DMFS scores, revealed a correlation coefficient of 0.71. Although the index purports to measure the prevalence and severity of dental caries by dividing the dentition into five zones representing increasing severity of dental caries experience, an analysis of this index's internal validity, i.e. whether these five zones truly represent a rank-order scale of severity, revealed misclassification rates of from 21% for the total population up to 44% for a subgroup. When zones were recombined to reduce the misclassification rates, the descriptive capabilities of the index were greatly reduced as most subjects were then classified in only one or two of the zones.