Evaluating the Validity of Probing Attachment Loss as a Surrogate for Tooth Mortality in a Clinical Trial on the Elderly

• Published in: Journal of dental research Vol. 76; no. 4; pp. 858 - 866
• Main Authors: Hujoel, P.P., Leroux, B.G., DeRouen, T.A., Powell, L.V., Kiyak, H.A.
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01.04.1997; SAGE PUBLICATIONS, INC
• Subjects: Aged; Analysis of Variance; Anti-Infective Agents, Local - therapeutic use; Behavior Therapy; Chlorhexidine - therapeutic use; Clinical Trials as Topic - methods; Confidence Intervals; Dental Care for Aged - methods; Dental Prophylaxis; Dental Research - methods; Dentistry; Fluorides, Topical - therapeutic use; Humans; Outcome Assessment (Health Care); Periodontal Attachment Loss - diagnosis; Periodontal Attachment Loss - therapy; Periodontal Pocket - diagnosis; Periodontics - instrumentation; Predictive Value of Tests; Prognosis; Regression Analysis; Reproducibility of Results; Risk Assessment; Tooth Loss - diagnosis; Tooth Loss - prevention & control; probing attachment level; geriatrics; surrogate endpoints; randomized controlled trial
• ISSN: 0022-0345; 1544-0591
• DOI: 10.1177/00220345970760040701

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.