RELIABILITY OF ATTACHMENT LOSS MEASUREMENTS IN A LONGITUDINAL CLINICAL-TRIAL

Abstract In order to appropriately carry out a longitudinal assessment of periodontal attachment loss in individuals with untreated periodontitis, reliable criteria for determining “real” changes in attachment level (AL) are required. In the present study, 25 subjects were to be examined every 2 months for up to 2 years to determine changes in AL and to relate clinical and laboratory criteria to such changes. Trained examiners for the study underwent calibration trials to determine inter‐examiner and intra‐examiner reliability both before the study and at intervals during the study. It was found that AL measurements were in agreement within 2 mm more than 95% of the time. The calibration trials provided an estimate of the error in attachment loss measurements, since no “real” attachment loss had occurred. From estimates of measurement error, the probability of false positive changes were determined. It was found that acceptable false positive rates (< 5%) could be achieved if 2 examiners each detected 3 mm change at a given site or if 2 examiners each detected 2 mm change at a site and verified that this change persisted at a subsequent examination. The results of the longitudinal trial were then compared to the probability estimates calculated from the calibration trials. It was found that probabilities of AL changes detected during the longitudinal trial for less stringent conditions than described above (e.g., single examiner, 2 examiners unconfirmed) were similar to previously estimated false positive rates. However, under conditions chosen for confirmation of AL change (2 examiners confirmed), the actual % of examinations in which at least 1 site changed was considerably greater than predicted (28% versus 5%), indicating that true AL change had likely been detected. Thus, detection of AL change with a standard periodontal probe in a longitudinal study is reliable when 2 examiners each detect a change in AL of 3 mm from baseline or when 2 examiners each detect a 2 mm change that is confirmed at a subsequent examination. Furthermore, calibration trials provide a good estimate of expected rates of measurement error during a subsequent longitudinal trial. Copyright © 1990, Wiley Blackwell. All rights reserved