Using only Hα chemical shifts and simple clustering rules (clusters of 3 or more vertical bars for beta strands and clusters of 4 or more vertical bars for alpha helices), the CSI is typically 75-80% accurate in the identification of secondary structures. This performance depends partly on the quality of the NMR data set as well as the technique (manual or programmatic) used to identify the protein secondary structures.  As noted above, a consensus CSI method that filters upfield/downfield chemical shift changes in Cα, Cβ, and C' atoms in a similar manner to Hα shifts has also been developed.  The consensus CSI combines the CSI plots from backbone H and C chemical shifts to generate a single CSI plot. It can be up to 85-90% accurate.