What is the detection limit of protocol in scRNA-seq In Shapiro et al., when discussing about loss of molecules as source of error in single-cell sequencing, it is written that:


  Another source of error is losses, which can be severe. The detection limit of published protocols is $5$–$10$ molecules of mRNA.


I used to think that the detection limit of a protocol was the average maximum number of molecules detected across cells in a scRNA-seq experiment. However, by working on the dataset provided by The Tabula Muris Consortium et al. (pp) I noticed that RNA raw counts often spikes to more than 10 molecules.

What is the actual meaning of detection limit of a protocol in scRNA-seq?
The detection limit refers to the ability to detect a given gene/transcript. In this case, they're saying that a given transcript requires 5-10 copies in order to be likely detected (in other words, the loss rate is 80-90%, which is directly related to a previous question of yours).