Brief background of Viral load test
Within three to six weeks of exposure to HIV, infected individuals generally develop a brief, acute syndrome characterized by flu like symptoms and associated with high levels of viremia in peripheral blood. In most infected individuals, this is followed by an HIV specific immune response and a decline of plasma viremia, usually with in four to six weeks of the onset of the symptoms. After seroconversion, infected individuals typically enter a clinically stable, asymptomatic phase that can last for years. The asymptomatic period is characterized by persistent low level viremia, and a gradual depletion of the CD4 T-lymphocytes, leading to severe immunodeficiency, multiple opportunistic infections, malignancies and death.
Quantitative measurements of HIV viremia in the peripheral blood have shown that higher virus levels may be correlated with increased risk of clinical progression of HIV disease and that reductions in plasma virus levels may be associated with reduced risk of clinical progression.
Virus levels in peripheral blood can be quantitated by direct measurement of viral RNA in plasma using nucleic acid amplification e.g Polymerase Chain Reaction (PCR) or signal amplification technologies.
There are two major procedures used to determine virus levels in peripheral blood:
- Standard Procedure – Detects from 400 to over 750,000 copies of viral RNA in plasma samples.
The Amplicor HIV-1 Monitor Test, version 1.5 kit from Roche Company is used and is based on five major steps:
- Specimen Preparation
- Reverse transcription of target RNA to generate complementary DNA
- PCR amplification of target complementary DNA using HIV-1 specific complementary primers
- Hybridization of the amplified DNA to oligonucleotide probes specific to the targets
- Detection of the probe-bound amplified DNA by calorimetric determination.
- Ultra Sensitive Procedure – Detects very low viral RNA copies (< 400 copies). Two types of samples can be used with this procedure; that’s Plasma from whole Blood and swabs (Endocervical samples).
The Amplicor HIV-1 Monitor Test, version 1.5 Kit from Roche company is used and the five major steps are followed as in standard procedure.
As CFAR laboratories, we are happy to offer this service to our clients for either patient use of research.