title: Modelling changes in clinical attachment loss to classify periodontal disease progression.
abstract: The goal of this study was to identify progressing periodontal sites by applying linear mixed models (LMM) to longitudinal measurements of clinical attachment loss (CAL).
  
  
  
  Ninety-three periodontally healthy and 236 periodontitis subjects had their CAL measured bi-monthly for 12 months. The proportions of sites demonstrating increases in CAL from baseline above specified thresholds were calculated for each visit. The proportions of sites reversing from the progressing state were also computed. LMM were fitted for each tooth site and the predicted CAL levels used to categorize sites regarding progression or regression. The threshold for progression was established based on the model-estimated error in predictions.
  
  
  
  Over 12 months, 21.2%, 2.8% and 0.3% of sites progressed, according to thresholds of 1, 2 and 3 mm of CAL increase. However, on average, 42.0%, 64.4% and 77.7% of progressing sites for the different thresholds reversed in subsequent visits. Conversely, 97.1%, 76.9% and 23.1% of sites classified as progressing using LMM had observed CAL increases above 1, 2 and 3 mm after 12 months, whereas mean rates of reversal were 10.6%, 30.2% and 53.0% respectively.
  
  
  
  LMM accounted for several sources of error in longitudinal CAL measurement, providing an improved method for classifying progressing sites.
authors.affiliation: Department of Periodontology, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.|Department of Applied Oral Sciences, Forsyth Institute, Cambridge, MA, USA.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Teles
authors.affiliation: Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Habtamu K
authors.initials: HK
authors.lastname: Benecha
authors.affiliation: Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Preisser
authors.affiliation: Department of Dental Ecology, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Moss
authors.affiliation: Department of Applied Oral Sciences, Forsyth Institute, Cambridge, MA, USA.|Department of Oral Health Policy and Epidemiology, Harvard School of Dental Medicine, Harvard University, Boston, MA, USA.
authors.forename: Jacqueline R
authors.initials: JR
authors.lastname: Starr
authors.affiliation: New York University College of Dentistry, Bluestone Center for Clinical Research, New York, NY, USA.
authors.forename: Patricia
authors.initials: P
authors.lastname: Corby
authors.affiliation: Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, Buffalo, NY, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Genco
authors.affiliation: Section of Periodontics, Department of Applied Dental Medicine, Southern Illinois University School of Dental Medicine, Alton, IL, USA.
authors.forename: Nathalia
authors.initials: N
authors.lastname: Garcia
authors.affiliation: Department of Periodontics and Oral Medicine & Michigan Center for Oral Health Research, University of Michigan School of Dentistry, Ann Arbor, MI, USA.
authors.forename: William V
authors.identifier: 0000-0002-7102-9746
authors.initials: WV
authors.lastname: Giannobile
authors.affiliation: Rho Inc., Contract Research Organization, Chapel Hill, NC, USA.
authors.forename: Heather
authors.initials: H
authors.lastname: Jared
authors.affiliation: Department of Applied Oral Sciences, Forsyth Institute, Cambridge, MA, USA.
authors.forename: Gay
authors.initials: G
authors.lastname: Torresyap
authors.affiliation: Department of Applied Oral Sciences, Forsyth Institute, Cambridge, MA, USA.
authors.forename: Elida
authors.initials: E
authors.lastname: Salazar
authors.affiliation: New York University College of Dentistry, Bluestone Center for Clinical Research, New York, NY, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Moya
authors.affiliation: New York University College of Dentistry, Bluestone Center for Clinical Research, New York, NY, USA.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Howard
authors.affiliation: Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, Buffalo, NY, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Schifferle
authors.affiliation: Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, Buffalo, NY, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Falkner
authors.affiliation: Section of Periodontics, Department of Applied Dental Medicine, Southern Illinois University School of Dental Medicine, Alton, IL, USA.
authors.forename: Jane
authors.initials: J
authors.lastname: Gillespie
authors.affiliation: Section of Periodontics, Department of Applied Dental Medicine, Southern Illinois University School of Dental Medicine, Alton, IL, USA.
authors.forename: Debra
authors.initials: D
authors.lastname: Dixon
authors.affiliation: Department of Applied Oral Sciences, Forsyth Institute, Cambridge, MA, USA.
authors.forename: MaryAnn
authors.initials: M
authors.lastname: Cugini
mesh_terms: D018450:Disease Progression; D006801:Humans; D008137:Longitudinal Studies; D017622:Periodontal Attachment Loss; D010510:Periodontal Diseases; D010514:Periodontal Pocket
keywords: clinical attachment loss; disease progression; linear mixed models; periodontal disease