Sensitivity of the RCA assay. RCA was performed on 10-fold serial dilutions of the target template ranging from 1011 to 100 copies of target template (PCR product). The figure illustrates the RCA reaction using the Ca-Y132H-specific probe to detect 1011, 1010 and 109 copies of the template containing the Y132H mutation (obtained from amplifying DNA from isolate C594). RCA signals are shown as exponential increases in florescence signal above baseline (indicated by the "negative signal" label and defined as the signal obtained when amplifying target template that did not have the mutation of interest). The intensity of the signal weakened with decreasing copy numbers starting at 1011copies and the sensitivity of the assay corresponded to a concentration of 109copies of target template.