Coamplified positive control detects inhibition of polymerase chain reactions

Polymerase chain reactions (PCR) may fail to react because the substrate DNA is absent (true negative) or because of inhibition of specific amplification (false negative). The use of positive controls can increase confidence in negative PCR results by ruling out failure due to inhibition as a cause of the lack of amplification products. This report describes the construction and application of coamplified positive controls for herpes simplex virus and human herpesvirus 6 amplifications. Herpes simplex virus and human herpesvirus 6 PCR products were modified to generate control PCR products in which the original probe sequences were replaced by a Drosophila probe sequence. Implementation of the coamplified controls increased our specimen throughput in comparison with the parallel control amplifications used previously. Clinical laboratories using PCR for diagnosis of infectious diseases may find positive controls particularly helpful for increasing confidence that negative amplifications represent truly negative specimens.