Option-4 algorithm for third generation disc probe: Agreement of selected site-specific relative attachment level measurements and detection of longitudinal site-specific attachment level change

Background: Longitudinal site-specific attachment level change (SSAC), identified from serial relative attachment level measurements (RAL), is the principal indicator of progression/regression of periodontal diseases. Many variables confound RAL reproducibility and affect measurement error. The Option-4 algorithm was designed to reduce measurement error and improve accuracy and sensitivity of SSAC detection. The study aimed to evaluate the performance of the Option-4 algorithm. Methods: A precalibrated clinician recorded full mouth RAL with a third generation disc probe on 4 occasions over 6 months in 16 subjects (mean age 48.1 years) with moderately advanced chronic adult periodontitis (2,312 sites). Option-4 allowed up to 4 RAL recordings per site per visit until 2 values had differences less than or equal to 1.0 mm and their mean was 11.0 mm from the previous visit mean: the clinician made the selection if these criteria were unfulfilled. Results: Within-visit agreement less than or equal to 1.0 mm was greater than or equal to 99.6%: all within-visit correlation coefficients = 0.98 (P <0.001). At each visit, mean difference in Option-4 values was < 0.05 mm, mean absolute difference (ignoring direction) was less than or equal to 0.34 mm. Mean site-specific variances ranged from 0.092 mm(2) to 0.097 mm2 across all visits. Subject thresholds for site-specific attachment level change (from estimated 95% confidence limits of visit 1 data) ranged from 0.52 mm to 0.67 mm. Linear SSAC (by linear regression) and between-visit patterns of SSAC were investigated. SSAC was detected in 100% subjects and at 51.0% measured sites. Linear SSAC (R-2 greater than or equal to 0.90: P less than or equal to 0.05) occurred at 105 sites (4.5%): 32 sites (1.4%) deteriorated, 73 sites (3.1%) improved. Between-visit SSAC occurred at 1,074 sites (46.5%): 391 sites (16.9%) deteriorated, 295 sites (12.8%) improved, and 388 sites (16.8%) showed exacerbation/remission patterns. Conclusions: The Option-4 algorithm produced high RAL agreement. Site-specific attachment level change was detected in both directions in 100% subjects and at 51.0% measured sites.