title: Evaluating the validity of probing attachment loss as a surrogate for tooth mortality in a clinical trial on the elderly.
abstract: Most periodontal trials are based on the assumption that the superior treatment, as judged by short-term intangible changes in probing attachment levels (the surrogate), is also the treatment most likely to affect tooth mortality. This assumption is valid if: (1) the surrogate is informative about tooth mortality, and (2) the surrogate captures a substantial proportion of the treatment effect on tooth mortality (e.g., > 50% or 75%). The goal of this study was to evaluate whether both conditions were satisfied in a randomized controlled trial (RCT) of elders at high risk for dental diseases. The results suggested that the first condition for a valid surrogate was satisfied: Both one- and two-year changes in probing attachment level were informative about tooth mortality risk. A 1-mm loss measured over a one-year period was associated with a 56% increased tooth mortality risk (relative risk = 1.56; 95% confidence interval, 1.08 to 2.26; p = 0.017); a 1-mm loss measured over a two-year period was associated with a 102% increased risk for tooth mortality (relative risk = 2.02; 95% confidence interval, 1.26 to 3.25; p = 0.004). The second condition necessary for a valid surrogate could not be confirmed in the present trial. With 95% confidence, it was concluded that one-year changes in probing attachment level measurements did not capture a significant proportion of the treatment effect (point estimate, 6%; 95% confidence interval;-38% to 53%). No useful statements could be made regarding the proportion of treatment effect captured by two-year changes, due to the width of the confidence interval (point estimate, 18%; 95% confidence interval;-151% to 140%). It is concluded that (1) the evidence surrounding the one-year change in probing attachment level indicates that it can be ruled out as being anything more than a weak surrogate marker for tooth mortality, and (2) further research is required to study the validity of two-year change in probing attachment level as a surrogate marker. Due to characteristics of the population and the treatments investigated, the generalizability of these findings to other RCTs is questionable.
authors.affiliation: Department of Dental Public Health Sciences, School of Dentistry, University of Washington, Seattle 98195, USA.
authors.forename: P P
authors.initials: PP
authors.lastname: Hujoel
authors.forename: B G
authors.initials: BG
authors.lastname: Leroux
authors.forename: T A
authors.initials: TA
authors.lastname: DeRouen
authors.forename: L V
authors.initials: LV
authors.lastname: Powell
authors.forename: H A
authors.initials: HA
authors.lastname: Kiyak
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D000891:Anti-Infective Agents, Local / Q000627:therapeutic use; D001521:Behavior Therapy; D002710:Chlorhexidine / Q000627:therapeutic use; D002986:Clinical Trials as Topic / Q000379:methods; D016001:Confidence Intervals; D016321:Dental Care for Aged / Q000379:methods*; D003777:Dental Prophylaxis; D018865:Dental Research / Q000379:methods; D005460:Fluorides, Topical / Q000627:therapeutic use; D006801:Humans; D017063:Outcome Assessment, Health Care; D017622:Periodontal Attachment Loss / Q000175:diagnosis* / Q000628:therapy*; D010514:Periodontal Pocket / Q000175:diagnosis; D010517:Periodontics / Q000295:instrumentation; D011237:Predictive Value of Tests; D011379:Prognosis; D012044:Regression Analysis; D015203:Reproducibility of Results; D018570:Risk Assessment; D016388:Tooth Loss / Q000175:diagnosis* / Q000517:prevention & control
chemical_list: D000891:Anti-Infective Agents, Local; D005460:Fluorides, Topical; D002710:Chlorhexidine