midSIN measures the infectious dose in SIN
The infection concentration of a virus sample has traditionally been quantified in units of plaque or focus forming units (PFU or FFU) or 50% tissue culture or cell culture or egg infectious dose (TCID50, CCID50, EID50).
midSIN is a free, open-source tool (available on github) which calculates the SIN concentration of a virus sample based on the results of performing an endpoint dilution (TCID50) assay. SIN which stands for Specific INfections, is meant to replace all existing units (PFU, FFU, TCID50, ...) as a more biologically meaningful and accurate measure of a virus sample's infection concentration. A sample which contains 1 SIN/mL is expected to cause one infection per mL if the infection is conducted under the same conditions as the TCID50 assay (same cells, incubation time, etc.). See our paper for details, and please cite it if you use this tool.
Consider an example TCID50 assay on a 96-well plate with 11 different dilutions (D1 to D11), 8 repeats per dilution, and one column used for the virus-free control.
Imagine that the Well volume (virus sample + dilutant in each well) is 0.1 mL, the Starting dilution is 0.01 (100-fold), the Dilution factor between successive dilutions (e.g. D1 to D2) is 0.1 (10-fold), and you observed the above sample outcome. In such a case, midSIN would return
which indicates that your sample contained 108.983±0.1 SIN/mL. For more explanations about the results provided by midSIN, check out One sample where this example gets pre-loaded if you don't change any of the settings.