Improving efficiency in stereology: a study applying the proportionator and the autodisector on virtual slides

Cell counting in stereology is time-consuming. The proportionator is a new stereological sampling method combining automatic image analysis and non-uniform sampling. The autodisector on virtual slides combines automatic generation of disector pairs with the use of digital images. The aim of the study was to investigate the time efficiency of the proportionator and the autodisector on virtual slides compared with traditional methods in a practical application, namely the estimation of osteoclast numbers in paws from mice with experimental arthritis and control mice. Tissue slides were scanned in a digital slide scanner and the autodisector was applied on the obtained virtual tissue slides. Every slide was partitioned into fields of view, and cells were counted in all of them. Based on the original exhaustive data set comprising 100% of fields of view and covering the total section area, a proportionator sampling and a systematic, uniform random sampling were simulated. We found that the proportionator was 50% to 90% more time efficient than systematic, uniform random sampling. The time efficiency of the autodisector on virtual slides was 60% to 100% better than the disector on tissue slides. We conclude that both the proportionator and the autodisector on virtual slides may improve efficiency of cell counting in stereology.