Quantitative measures of aggressive periodontitis show substantial heritability and consistency with traditional diagnoses.
BACKGROUND
Aggressive periodontitis (AgP) research nearly always classifies subjects into traditional discrete categories of localized or generalized, based upon degree of attachment loss (AL) and types of affected teeth. Since AL is continuous and quantitative, however, useful information is lost. We developed quantitative measures of AgP, compared these to traditional methods, and estimated heritabilities in families.


METHODS
We examined 237 healthy, 169 localized AgP, and 204 generalized AgP subjects. We used the site of maximum AL of each tooth to calculate means for each subject for different groups of teeth. We also applied principal components analysis (PCA) to condense variation among 28 teeth into three orthogonal (uncorrelated) variables. We used discriminant function analysis (DFA) to evaluate how well the quantitative measures match with traditional classifications. Quantitative trait heritabilities were estimated by variance components.


RESULTS
PCA clustered first molars, incisors, and the other teeth into three groups. DFA showed that quantitative measures classified subjects consistent with traditional methods (87% to 94% agreement). Heritabilities ranged from 13.7% (P = 0.10) to 30.0% (P = 0.008) for quantitative measures, with highest values obtained for first molars. A combination of the principal component variables most heavily weighted on first molars and incisors gave the best model of disease susceptibility, with good separation of healthy versus diseased subjects, independent of disease extent or severity.


CONCLUSIONS
Quantitative measures may provide improved precision and power for many kinds of periodontal research. Our finding of significant heritability supports their use in gene mapping studies of AgP susceptibility.
Diehl
Scott R
SR
Center for Pharmacogenomics and Complex Disease Research, New Jersey Dental School, UMDNJ, Newark, NJ 07101, USA. diehlsr@umdnj.edu
Wu
Tianxia
T
Michalowicz
Bryan S
BS
Brooks
Carol N
CN
Califano
Joseph V
JV
Burmeister
John A
JA
Schenkein
Harvey A
HA
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D002908:Chronic Disease; D016002:Discriminant Analysis; D020022:Genetic Predisposition to Disease; D006801:Humans; D017622:Periodontal Attachment Loss / Q000473:pathology*; D010512:Periodontal Index; D010518:Periodontitis / Q000145:classification / Q000175:diagnosis* / Q000235:genetics*; D025341:Principal Component Analysis; D019655:Quantitative Trait, Heritable; D012720:Severity of Illness Index