Manifestations of Instrument-to-Instrument Variability on an Internal Control During Real-Time PCR

To the Editor: Using a laboratory- developed test, real-time PCR with the 3M Integrated Cycler (Focus Diagnostics) was used to amplify and detect in a single reaction the IS481 insertion sequenceof Bordetella pertussis, the IS1001 insertion sequenceof Bordetella parapertussis, and an internal control (IC)1 using channels that read FAM ( B. pertussis ), CAL Fluor Red 610 ( B. parapertussis ), and Quasar670 (IC). The IC consisted of exogenous DNA, IC primers, and an IC probe. A positive control containing a mixture of cultured B. pertussis (ATCC 9340) and B. parapertussis (ATCC 15311) was prepared and frozen in 215-μL aliquots. Patient specimens were nasopharyngeal swabs …