Elimination of false-positive polymerase chain reaction results resulting from hole punch carryover contamination

Nicolai Bonne, Phillip Clark, Patrick Shearer, Shane Raidal

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31 Citations (Scopus)
9 Downloads (Pure)


The collection of biological material (e.g., blood) directly onto filter paper for subsequent use in laboratory assays such as polymerase chain reaction (PCR), has become a common practice. Dried cells or fluid on the paper can be readily rehydrated and retrieved into a standard volume of an appropriate elution buffer but introduces a dilution factor to the sample. The use of a common cutting instrument for excising a standard-sized piece of paper that contains the material also introduces the potential for transferring biological material from one sample to subsequent samples, causing false-positive results by PCR. In the present study, filter-paper-collected blood that contained beak and feather disease virus was used to determine if viral DNA could be transferred between samples by a hole punch used to excise sequential filter papers. It was determined that false-positive results could be obtained at least 13 times after a positive sample. Subsequently, the efficacy of 4 methods of hole punch disinfection, flaming, VirkonS, bleach, and a bleachethanol combination, was assessed. The only effective and practical method to destroy DNA was a method where the hole punch was agitated in commercial bleach, rinsed in water, the water was displaced with 100% ethanol and air-dried. This method was simple, cheap, and relatively rapid, and allowed for the use of a single hole punch for a series of samples, without carryover contamination and consequent false-positive results.

Original languageEnglish
Pages (from-to)60-63
Number of pages4
JournalJournal of Veterinary Diagnostic Investigation
Issue number1
Publication statusPublished - 01 Jan 2008


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