Shedding More Light on Shedders

We report on testing 100 individuals for their shedder status with the aim of demonstrating whether the process of cell staining is reproducible when testing a large number of people. A previous report using the same method was based on 11 donors and indicated that there may be a continuum of shedder types within this small sample set. In this report we also expand the time points post-handwashing to 0, 15, 30, 60, and 180 minutes. Triplicate samples were collected from both the right and left thumbs. Samples were collected by donors placing a thumb on a clean glass slide and then adding a DNA binding dye. The number of cells were recorded within three separate square millimetre areas (cells/mm2) at 220x magnification. The experiments were conducted in triplicate on three different days, giving a total of 72 thumbprints per individual. Finally, there were 3,438 observed frames in the entire dataset. Of the 100 donors, 98 gave consistent and reproducible cell number deposition. There was no difference between the cells deposited by the left and right thumbs in 13 of 15 tested. Males tended to deposit more cells than females. If applying arbitrary boundary to a cell count to definitively determine shedder status, then many of the donors fell within two categories. This study based on 100 individuals strongly suggests that shedder status is a continuum phenomenon.