GeneSeq®

GeneSeq® is a highly accurate genotypic HIV drug resistance test. The test is performed using state-of-the-art technology and the results are determined using the most recently updated HIV mutation information and information from scientific research and Monogram's resistance experts.

About Genotyping

Genotypic testing looks for the presence of genetic changes, or mutations, in HIV to predict resistance to antiretroviral drugs. If the mutations found in a person's virus match the mutations that are known to cause resistance to a drug, then his or her virus is presumed to be resistant to that drug. The critical aspect of genotyping, however, is not identifying mutations but interpreting the results Ñ in other words, making sense of all the different mutations and how they interact with each other to affect drug susceptibility.

How Genotypic Testing Is Performed

There are two main types of genotypic resistance testing: sequencing assays and point mutation assays. Sequencing assays scan the complete sequence of gene, whereas point mutation assays look for mutations at specific locations, or codons, in the gene sequence. Though these assays differ in how the genetic structure is analyzed, they both start by using polymerase chain reaction (PCR) technology to amplify (copy) the viral RNA or DNA present in a patient's blood sample. PCR technology allows researchers to amplify specific genetic sequences in a person's HIV to create a sufficient amount for genotypic testing. The following example of how genotypic testing is performed is based on GeneSeq.

Step 1. Sample is taken

Step 2. Copies of the virus are made (using PCR technology, the genetic material of a person's HIV is copied numerous times)

Step 3. Genes within the virus (most commonly the reverse transcriptase and protease genes) are evaluated for mutations

Step 4. Mutations found in the virus are compared to known resistance mutations

Results: If the type and pattern of mutations present in a person's virus match pre-established mutations for a particular drug, the virus has probably developed resistance to that drug.

What Genotypic Test Results Mean

If genotypic testing reveals drug resistance mutations in a person's HIV, certain antiretroviral drugs may be less likely to work. The specific type and placement of the mutations determine which drugs the virus may be resistant to. For example, if the "M184V" mutation is discovered in a person's HIV, the virus is probably resistant to 3TC (lamivudine). Once a healthcare provider understands which drugs are less likely to work, she/he can develop a treatment plan that avoids the use of those drugs. This results in a therapy regimen that is more likely to be effective for a longer period of time.

How Genotypic Results Are Reported

Once the mutations present in a person's virus are identified, they are organized and listed on a report form. Mutations are usually listed by the drug category they pertain to Ñ nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), or protease inhibitors (PIs). Once the mutations are organized, they must be reviewed and compared to the most recent guidelines explaining what a given mutation or collection of mutations means; this step can be subjective.

Below is a sample GeneSeq report form to provide a better idea of how the drug resistance information is reported.

Download Sample GeneSeq Report