Validity and reliability of partial examination to assess severe periodontitis.

Objectives: To compare the extent and severity index (ESI) with a gold standard represented by actual readings of loss of attachment on six sites around all teeth present (excluding third molars).

Methods: Five standardized dentists (kappa=0.6) examined 712 subjects > or =20 years of age at a dental school (1993-1995). Sensitivity, specificity, positive and negative predictive values, and true and apparent prevalence were established.

Results: True severe periodontitis prevalence was 95.8%. ESI underestimated the severity (0.1 mm), extent (4%), and prevalence (16%) of periodontitis. The severity, as established by ESI, coincided 23.4% with the gold standard. ESI failed to identify 16.7% of subjects with severe periodontal disease, but specificity and positive predictive value were very high.

Conclusions: The underestimation of severe periodontitis through ESI may lead to inadequate recommendations for further treatment. Accurately identifying subjects with severe periodontitis requires a full-mouth examination. Because the ESI relies on measurements taken on only 28 periodontal sites to estimate the periodontitis status of the entire mouth, the validity and reliability of ESI may be modified by the prevalence of severe periodontal disease and the distribution of disease according to age and operational definitions.