Available Studies
ROS, MAP, MARS, Clinical Core, LATC
Categories
Pathology
Tangle density (after square root transformation) is based on historical and/or digital data and is the mean of the square root transformation of the tangle score in 8 regions:
Historical measures of tau-tangles were obtained from 20-micron sections from the 8 brain regions. Immunohistochemistry was performed using an antibody specific to phosphorylated tau, AT8 (1:2000, ThermoScientific). Using the Stereo Investigator software, regions of interest were manually outlined, and the systematic random sampling (SRS) grid was applied for manual counting. Manual counts of tau-tangles within a defined area were calculated as a density (count) per mm2. A square root transformation was applied.
Digital scanning of AT8-stained slides began in 2019 using the Aperio AT2 whole slide brightfield scanning system. Briefly, paraformaldehyde-fixed brain regions are sampled, embedded, sectioned at 6-microns, and subsequently stained using an AT8 antibody (1:2000, ThermoScientific). Pathology glass slides are loaded into the Aperio AT2 scanner console and processed to generate digital whole slide images. Digital image analysis for tau-tangles was quantified using the Aperio Image Analysis Toolbox Nuclear algorithm. The algorithm is applied to whole slide images from the 8 brain regions. Scoring parameters are set to specify weak, medium, and strong thresholds for tau-tangle staining intensity. Overall tau-tangle burden is calculated for each slide by adding up the nuclei with medium and strong threshold, and dividing by the analysis area, resulting in a value of nuclei in counts per mm2. A square root transformation is applied. Digital scores are reported as density of tangle counts per mm2, after square root transformation.
This variable harmonizes historical data with the new digital data for tau-tangles. The variable uses the new digital scores for tangles. If digital data is not available for a particular region, a digital score is predicted from the historical data. The mean of the 8 region values is calculated if data for at least 4 of the 8 regions are available.
This variable replaces "tangles" as the measure of tangle density.