Common complications include primer-dimer formation--which consumes reagents and reduces target amplification
and signal levels--and misamplification of very similar, off-target sequences.
Amped's high sensitivity and specificity will enable the direct detection of pathogens present in clinical samples, even when present in small amounts, without requiring polymerase chain reaction-based target amplification
, and when implemented in future tests will make it possible for Great Basin to provide PCR-like limits of detection at greatly reduced test times for certain targets of interest.
The Roche (version 1.5) assay is a reverse-transcription PCR-based, target amplification
assay targeting the gag p24 region of the genome.
Extent of target amplification
(e) is calculated as e = (ng DNA after PCR) / (ng of target DNA input), and the number of template doublings during PCR (d) can be calculated as e = [2.sup.d].
In the cycles that follow, the UniPrimer anneals to the tag and directs the target amplification
. During target duplication, the UniPrimer is unfolded and converted to a linear structure, with an increased distance between fluorophore and quencher, thereby resulting in restored emission (Fig.
Its assays are based on its STAR (Scalable Target Amplification
No risk of amplicon contamination Target amplification
PCR and variants Highly sensitive.
The GeneXpert[R] is a closed, contained system, with the ability to perform specimen preparation, target amplification
, and detection all in one sample device (cartridge).
Multiple target amplification
. Two different gene targets were tested using culture extracts and were shown to co-amplify without a loss in sensitivity (Table-5).
The principle of signal amplification is to directly detect nucleic acids without target amplification
by increasing the signalling capacity of the labelled molecules attached to the target nucleic acid eg.
The [C.sub.T] value represents the number of cycles required for target amplification
to reach the exponential phase and is therefore inversely related to initial target concentrations.
Moreover, the availability of target amplification
assays, such as polymerase chain reaction (PCR) assays, can now detect HBV DNA levels as low as 100-1,000 copies/mL.