Viral load assays are changing due to advanced technology to better serve both developed and developing countries. There are two main types of viral load assays: nucleic acid testing (NAT) technologies that detect and quantify viral RNA, and non-nucleic acid testing (NNAT) technologies that detect viral enzymes and proteins as a correlate of viral RNA. Common NAT methods include reverse transcription polymerase chain reaction (RT-PCR), nucleic acid sequence based amplification (NASBA), and branched chain DNA (bDNA). RT-PCR is commonly used to quantify HIV RNA and determine viral load. Examples of commercial viral load tests include Amplicor HIV-1 monitor v1.5, Cobas Taqman, and Real time HIV-1

1. Medical Laboratory Scientist
Nancy Somi

2.  Viral load is the concentration of virus in the
blood stream.
 Its used in conjunction with other tests to
monitor the progress of patients.

3.  Its used as a primary indicator of therapeutic
efficacy.
 Used to monitor a change in ARV drugs in
drug resistance cases
 It’s a baseline indicator of disease
progression.

4. Due to advanced technology viral load assays are dramatically
changing to fit the current setting of developed and developing
countries. These assays differ in.
 Sensitivity
 Dynamic range
 Target region
 Extraction, amplification and detection in nucleic acid based
assays.

5.  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
RNA.

6. Three major methods for detecting and quantifying
nucleic acids.
 Reverse transcription polymerase chain
reaction.(RT-PCR)
 Nucleic Acid Sequence Based
Amplification(NASBA)
 Branched chain DNA (bDNA)

7.  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.

8.  Amplicor HIV-1 monitor v1.5(Roche)
 Cobas Taqman (Roche)
 Real time HIV -1 (Abbot)
 VERSANT HIV-1 RNA ASSAY (kPCR)

9.  The COBAS Taqman is a real time PCR that
targets both the gag and LTR regions of the
HIV genome.
 Coupled with the COBAS Ampliprep, viral load
quantification is a fully automated process.
 It can detect as low as 20cp/ml.

10.  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.

11. “Science grows like a weed every year”.
Kary Mullis
THANK YOU!!!!!