Fig. 5.

Multicomponent plots for various amplification curve shapes. Optimal assays will produce a tall sigmoid curve (A), for which the QuantStudio software's default threshold value will often be appropriate. Some assays may produce more linear amplification curves (B), a smaller increase in fluorescence (C) or ambiguous curves (D). This may be a result of the assay's performance under the universal cycling conditions on the card, or may occur in certain sample types prone to PCR inhibition. For poorer curves, the appropriate C_q value may be difficult to determine.