Viral load is the concentration of virus in the
Its used in conjunction with other tests to
monitor the progress of patients.
Its used as a primary indicator of therapeutic
Used to monitor a change in ARV drugs in
drug resistance cases
It’s a baseline indicator of disease
Due to advanced technology viral load assays are dramatically
changing to fit the current setting of developed and developing
countries. These assays differ in.
Extraction, amplification and detection in nucleic acid based
Nucleic Acid Testing Technologies (NAT)-They
detect and quantify Viral RNA
Non-Nucleic Testing Technologies( NNAT)
They are based on the detection and
quantification of HIV viral enzymes and proteins
which can be used as a correlate measure of viral
Three major methods for detecting and quantifying
Reverse transcription polymerase chain
Nucleic Acid Sequence Based
Branched chain DNA (bDNA)
RT‐PCR is a method of PCR using a Reverse
Transcriptase (RT) enzyme to convert viral RNA
into complementary DNA (cDNA).
The cDNA undergoes replication and detection
. RT‐PCR is used to quantify HIV RNA and to
dertemine viral load.
Amplicor HIV-1 monitor v1.5(Roche)
Cobas Taqman (Roche)
Real time HIV -1 (Abbot)
VERSANT HIV-1 RNA ASSAY (kPCR)
The COBAS Taqman is a real time PCR that
targets both the gag and LTR regions of the
Coupled with the COBAS Ampliprep, viral load
quantification is a fully automated process.
It can detect as low as 20cp/ml.
Can only be accessed by developed countries
and a very few places in developing countries.
In developed countries it’s the most baseline
investigation in HIV positive patients.
“Science grows like a weed every year”.