The pervasive expression of circular RNAs (circRNAs) is a recently discovered 
feature of gene expression in highly diverged eukaryotes. Numerous algorithms 
that are used to detect genome-wide circRNA expression from RNA sequencing 
(RNA-seq) data have been developed in the past few years, but there is little 
overlap in their predictions and no clear gold-standard method to assess the 
accuracy of these algorithms. We review sources of experimental and 
bioinformatic biases that complicate the accurate discovery of circRNAs and 
discuss statistical approaches to address these biases. We conclude with a 
discussion of the current experimental progress on the topic.