Option-4 algorithm for automated disc probe: reduction in the variance of site-specific relative attachment level...

Physical periodontal measurement is plagued by many confounders which result in aberrant values. Replicate measurements can reduce the number of aberrant values, the measurement error, and the variance of site-specific measurements. This study aimed to reduce the variance of site-specific measurements by using a new clinical algorithm (the Option-4 algorithm) for an automated disk probe. A single clinician recorded full-mouth relative attachment levels (RAL) at one visit in 32 patients (mean age 45.5 years) with moderately advanced chronic adult periodontitis. RAL was recorded over two passes at six sites per tooth (4,675 sites). The algorithm accepted the first and second pass RALs (RAL1 and RAL2) if their difference was < or = 1 mm, otherwise a maximum of two further RALs (RAL3 and RAL4) were recorded until the difference between any two RALs was < or = 1 mm (SAL1 and SAL2): 4,048 sites (86.6%) required two recordings, 580 sites (12.4%) required three recordings and 47 sites (1%) required four recordings. Correlation coefficients for RAL1 and RAL2 and SAL1 and SAL2 (4,675 sites) were both > or = 0.91 (P = 0.00). Site-specific variances were calculated for RAL1 and RAL2 and SAL1 and SAL2. The mean of the RAL1/RAL2 site-specific variances (A) was 0.45 mm2 (range 0.00 mm2 to 35.28 mm2) whilst the mean of the SAL1/SAL2 variances (B) was 0.09 mm2 (range 0.00 mm2 to 0.5 mm2): the respective medians were 0.08 mm2 and 0.02 mm2. The study demonstrated high intra-examiner RAL reproducibility. The Option-4 algorithm produced an 80% reduction in the mean site-specific variance of RAL1/RAL2 (Y) and a 75% reduction in the median site-specific variance of RAL1/RAL2 (y = [(A - B)/A] x 100).