Table 2 Advantages and disadvantages of three types of molecular analytical positive controls

• Can be used in the absence of wild-type control material

• Qualitative only not quantitative

• Reduced contamination

• Cannot be used for low viral loads

• DNA and RNA compatible

• Greater risk of primer dimer formation

• Quick and simple method

• Interim solution until wild-type material is available

• Does not account for sequence variation in clinical material

• DNA and RNA compatible

• Synthetic oligonucleotides must be less than 200 bp

• Reduced contamination (does not require cloning)

• Can be expensive if target is large

• Production of a synthetic oligonucleotide and clone into a plasmid

• Target sequence must be known

• No possibility of producing false-positives

• Requires two separate control reactions (primer and probe)

• Can be used for rtPCR and conventional PCR

• Pre-made available (other labs or PlasmID repository)

• Requires shipping

• Difficult to distinguish contamination from clinical material

• Cost effective

• Can be quantitative and qualitative

• Possible contamination

• Can be quantitative and qualitative

• Requires clinical material or live virus

• Cost effective

• Requires cloning (time consuming)

• Can easily be produced

• Difficult to distinguish contamination from clinical material

• Possible contamination