HIV-1 Drug Resistance
Testing

Personalised care for patients with HIV-1 infection

What is HIV-1 drug resistance testing?
This involves analysing the sequence of a portion of the HIV-1 genome which indicates resistance against anti-retroviral treatment. HIV-1 genotyping deciphers the viral genetic material and identifies potential resistance of the virus against anti-retroviral drugs such as Protease Inhibitors or Reverse Transcriptase (RT) Inhibitors, Nucleoside and Nucleotide RT Inhibitors. The HIV-1 genotype of an infected individual reflects the presence or absence of mutations in viral RNA associated with anti-retroviral resistance. All newly-diagnosed patients with HIV-1 infection are now recommended to have genotypic resistance analysis prior to the commencement of therapy.

HIV drug resistance testing is not intended to be used as a screening test for HIV or as a diagnostic test to confirm the presence of HIV infection.

Used in conjunction with clinical presentation, laboratory markers, and antiretroviral history as an adjunct to the therapeutic management of patients with HIV-1, subtype B, and a minimum viral load of >1,000 RNA copies/mL.

What technique is used in HIV-1 drug resistance testing?
Genotyping is carried out using DNA sequencing. Viral RNA extracted from plasma is transcribed to complementary DNA and amplified in a single-tube reverse transcription polymerase chain reaction. The amplified DNA product is sequenced in both directions with a modified Sanger technique; using fluorescent dye labelled primers and automated laser detection. Drug resistance software interprets the HIV-1 genotype using a wild type sequence as a reference. An easy to understand Resistance Interpretation Report incorporates in vitro phenotypic and in vivo virological response data powered by algorithms; GuideLines™ Rules and also lists the type/weight of data (Evidence Basis).

The Resistance Report is supported by detailed listing of rules and Evidence Basis used for each drug. The lists of guidelines rules used and Evidence Basis used for each drug to make an interpretation is created from a combination of independent virological response data from clinical trials, in vitro phenotypic data or in vitro demonstration of mutation selection.

Extrapolation of data is used where in vitro or in vivo data does not exist. This is based on indirect evidence of resistance effects provided by data from similar drugs and/or mutation patterns. This is only included when a particular drug is part of routine clinical practice.

What is included in the HIV-1 drug resistance report?
At-a-glance colour coded resistance summary which lists mutations present indicating position of specific mutations at recognized mutation sites, as well as silent mutations, polymorphisms and unexpected mutations at resistance sites. The report also includes a list of antiretroviral drugs by generic drug names and resistance interpretation for each (FDA approved and expanded access drugs).

How does the testing service work?

Why choose the test?

• Reduce costs in using highly expensive therapies that have no value against specific resistance patterns.
• Individuals using HIV-1 combination therapy can have their HIV-1 drug resistance tested to evaluate the possibility of HIV-1 drug resistance against each drug they are taking. Multiple mutations to different drugs can then be identified.
• Reduce the frequency of adverse drug events associated with some drugs which are of no value against resistant strains.
• Improve individuals prognosis, therefore slow down progression to AIDS.

*Viral load of >1,000 RNA copies/ml to be confirmed first